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Registered in England and Wales under Company Registration No. 3798903 Subject: [RFC PATCH 06/12] netfs: Keep lists of pending, active, dirty and flushed regions From: David Howells To: linux-fsdevel@vger.kernel.org Cc: dhowells@redhat.com, Jeff Layton , "Matthew Wilcox (Oracle)" , Anna Schumaker , Steve French , Dominique Martinet , Mike Marshall , David Wysochanski , Shyam Prasad N , Miklos Szeredi , Linus Torvalds , linux-cachefs@redhat.com, linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net, devel@lists.orangefs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Wed, 21 Jul 2021 14:46:08 +0100 Message-ID: <162687516812.276387.504081062999158040.stgit@warthog.procyon.org.uk> In-Reply-To: <162687506932.276387.14456718890524355509.stgit@warthog.procyon.org.uk> References: <162687506932.276387.14456718890524355509.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org This looks nice, in theory, and has the following features: (*) Things are managed with write records. (-) A WRITE is a region defined by an outer bounding box that spans the pages that are involved and an inner region that contains the actual modifications. (-) The bounding box must encompass all the data that will be necessary to perform a write operation to the server (for example, if we want to encrypt with a 64K block size when we have 4K pages). (*) There are four list of write records: (-) The PENDING LIST holds writes that are blocked by another active write. This list is in order of submission to avoid starvation and may overlap. (-) The ACTIVE LIST holds writes that have been granted exclusive access to a patch. This is in order of starting position and regions held therein may not overlap. (-) The DIRTY LIST holds a list of regions that have been modified. This is also in order of starting position and regions may not overlap, though they can be merged. (-) The FLUSH LIST holds a list of regions that require writing. This is in order of grouping. (*) An active region acts as an exclusion zone on part of the range, allowing the inode sem to be dropped once the region is on a list. (-) A DIO write creates its own exclusive region that must not overlap with any other dirty region. (-) An active write may overlap one or more dirty regions. (-) A dirty region may be overlapped by one or more writes. (-) If an active write overlaps with an incompatible dirty region, that region gets flushed, the active write has to wait for it to complete. (*) When an active write completes, the region is inserted or merged into the dirty list. (-) Merging can only happen between compatible regions. (-) Contiguous dirty regions can be merged. (-) If an inode has all new content, generated locally, dirty regions that have contiguous/ovelapping bounding boxes can be merged, bridging any gaps with zeros. (-) O_DSYNC causes the region to be flushed immediately. (*) There's a queue of groups of regions and those regions must be flushed in order. (-) If a region in a group needs flushing, then all prior groups must be flushed first. TRICKY BITS =========== (*) The active and dirty lists are O(n) search time. An interval tree might be a better option. (*) Having four list_heads is a lot of memory per inode. (*) Activating pending writes. (-) The pending list can contain a bunch of writes that can overlap. (-) When an active write completes, it is removed from the active queue and usually added to the dirty queue (except DIO, DSYNC). This makes a hole. (-) One or more pending writes can then be moved over, but care has to be taken not to misorder them to avoid starvation. (-) When a pending write is added to the active list, it may require part of the dirty list to be flushed. (*) A write that has been put onto the active queue may have to wait for flushing to complete. (*) How should an active write interact with a dirty region? (-) A dirty region may get flushed even whilst it is being modified on the assumption that the active write record will get added to the dirty list and cause a follow up write to the server. (*) RAM pinning. (-) An active write could pin a lot of pages, thereby causing a large write to run the system out of RAM. (-) Allow active writes to start being flushed whilst still being modified. (-) Use a scheduler hook to decant the modified portion into the dirty list when the modifying task is switched away from? (*) Bounding box and variably-sized pages/folios. (-) The bounding box needs to be rounded out to the page boundaries so that DIO writes can claim exclusivity on a series of pages so that they can be invalidated. (-) Allocation of higher-order folios could be limited in scope so that they don't escape the requested bounding box. (-) Bounding boxes could be enlarged to allow for larger folios. (-) Overlarge bounding boxes can be shrunk later, possibly on merging into the dirty list. (-) Ordinary writes can have overlapping bounding boxes, even if they're otherwise incompatible. --- fs/afs/file.c | 30 + fs/afs/internal.h | 7 fs/afs/write.c | 166 -------- fs/netfs/Makefile | 8 fs/netfs/dio_helper.c | 140 ++++++ fs/netfs/internal.h | 32 + fs/netfs/objects.c | 113 +++++ fs/netfs/read_helper.c | 94 ++++ fs/netfs/stats.c | 5 fs/netfs/write_helper.c | 908 ++++++++++++++++++++++++++++++++++++++++++ include/linux/netfs.h | 98 +++++ include/trace/events/netfs.h | 180 ++++++++ 12 files changed, 1604 insertions(+), 177 deletions(-) create mode 100644 fs/netfs/dio_helper.c create mode 100644 fs/netfs/objects.c create mode 100644 fs/netfs/write_helper.c diff --git a/fs/afs/file.c b/fs/afs/file.c index 1861e4ecc2ce..8400cdf086b6 100644 --- a/fs/afs/file.c +++ b/fs/afs/file.c @@ -30,7 +30,7 @@ const struct file_operations afs_file_operations = { .release = afs_release, .llseek = generic_file_llseek, .read_iter = generic_file_read_iter, - .write_iter = afs_file_write, + .write_iter = netfs_file_write_iter, .mmap = afs_file_mmap, .splice_read = generic_file_splice_read, .splice_write = iter_file_splice_write, @@ -53,8 +53,6 @@ const struct address_space_operations afs_file_aops = { .releasepage = afs_releasepage, .invalidatepage = afs_invalidatepage, .direct_IO = afs_direct_IO, - .write_begin = afs_write_begin, - .write_end = afs_write_end, .writepage = afs_writepage, .writepages = afs_writepages, }; @@ -370,12 +368,38 @@ static void afs_priv_cleanup(struct address_space *mapping, void *netfs_priv) key_put(netfs_priv); } +static void afs_init_dirty_region(struct netfs_dirty_region *region, struct file *file) +{ + region->netfs_priv = key_get(afs_file_key(file)); +} + +static void afs_free_dirty_region(struct netfs_dirty_region *region) +{ + key_put(region->netfs_priv); +} + +static void afs_update_i_size(struct file *file, loff_t new_i_size) +{ + struct afs_vnode *vnode = AFS_FS_I(file_inode(file)); + loff_t i_size; + + write_seqlock(&vnode->cb_lock); + i_size = i_size_read(&vnode->vfs_inode); + if (new_i_size > i_size) + i_size_write(&vnode->vfs_inode, new_i_size); + write_sequnlock(&vnode->cb_lock); + fscache_update_cookie(afs_vnode_cache(vnode), NULL, &new_i_size); +} + const struct netfs_request_ops afs_req_ops = { .init_rreq = afs_init_rreq, .begin_cache_operation = afs_begin_cache_operation, .check_write_begin = afs_check_write_begin, .issue_op = afs_req_issue_op, .cleanup = afs_priv_cleanup, + .init_dirty_region = afs_init_dirty_region, + .free_dirty_region = afs_free_dirty_region, + .update_i_size = afs_update_i_size, }; int afs_write_inode(struct inode *inode, struct writeback_control *wbc) diff --git a/fs/afs/internal.h b/fs/afs/internal.h index e0204dde4b50..0d01ed2fe8fa 100644 --- a/fs/afs/internal.h +++ b/fs/afs/internal.h @@ -1511,15 +1511,8 @@ extern int afs_check_volume_status(struct afs_volume *, struct afs_operation *); * write.c */ extern int afs_set_page_dirty(struct page *); -extern int afs_write_begin(struct file *file, struct address_space *mapping, - loff_t pos, unsigned len, unsigned flags, - struct page **pagep, void **fsdata); -extern int afs_write_end(struct file *file, struct address_space *mapping, - loff_t pos, unsigned len, unsigned copied, - struct page *page, void *fsdata); extern int afs_writepage(struct page *, struct writeback_control *); extern int afs_writepages(struct address_space *, struct writeback_control *); -extern ssize_t afs_file_write(struct kiocb *, struct iov_iter *); extern int afs_fsync(struct file *, loff_t, loff_t, int); extern vm_fault_t afs_page_mkwrite(struct vm_fault *vmf); extern void afs_prune_wb_keys(struct afs_vnode *); diff --git a/fs/afs/write.c b/fs/afs/write.c index a244187f3503..e6e2e924c8ae 100644 --- a/fs/afs/write.c +++ b/fs/afs/write.c @@ -27,152 +27,6 @@ int afs_set_page_dirty(struct page *page) return fscache_set_page_dirty(page, afs_vnode_cache(AFS_FS_I(page->mapping->host))); } -/* - * Prepare to perform part of a write to a page. Note that len may extend - * beyond the end of the page. - */ -int afs_write_begin(struct file *file, struct address_space *mapping, - loff_t pos, unsigned len, unsigned flags, - struct page **_page, void **fsdata) -{ - struct afs_vnode *vnode = AFS_FS_I(file_inode(file)); - struct page *page; - unsigned long priv; - unsigned f, from; - unsigned t, to; - int ret; - - _enter("{%llx:%llu},%llx,%x", - vnode->fid.vid, vnode->fid.vnode, pos, len); - - /* Prefetch area to be written into the cache if we're caching this - * file. We need to do this before we get a lock on the page in case - * there's more than one writer competing for the same cache block. - */ - ret = netfs_write_begin(file, mapping, pos, len, flags, &page, fsdata); - if (ret < 0) - return ret; - - from = offset_in_thp(page, pos); - len = min_t(size_t, len, thp_size(page) - from); - to = from + len; - -try_again: - /* See if this page is already partially written in a way that we can - * merge the new write with. - */ - if (PagePrivate(page)) { - priv = page_private(page); - f = afs_page_dirty_from(page, priv); - t = afs_page_dirty_to(page, priv); - ASSERTCMP(f, <=, t); - - if (PageWriteback(page)) { - trace_afs_page_dirty(vnode, tracepoint_string("alrdy"), page); - goto flush_conflicting_write; - } - /* If the file is being filled locally, allow inter-write - * spaces to be merged into writes. If it's not, only write - * back what the user gives us. - */ - if (!test_bit(NETFS_ICTX_NEW_CONTENT, &vnode->netfs_ctx.flags) && - (to < f || from > t)) - goto flush_conflicting_write; - } - - *_page = find_subpage(page, pos / PAGE_SIZE); - _leave(" = 0"); - return 0; - - /* The previous write and this write aren't adjacent or overlapping, so - * flush the page out. - */ -flush_conflicting_write: - _debug("flush conflict"); - ret = write_one_page(page); - if (ret < 0) - goto error; - - ret = lock_page_killable(page); - if (ret < 0) - goto error; - goto try_again; - -error: - put_page(page); - _leave(" = %d", ret); - return ret; -} - -/* - * Finalise part of a write to a page. Note that len may extend beyond the end - * of the page. - */ -int afs_write_end(struct file *file, struct address_space *mapping, - loff_t pos, unsigned len, unsigned copied, - struct page *subpage, void *fsdata) -{ - struct afs_vnode *vnode = AFS_FS_I(file_inode(file)); - struct page *page = thp_head(subpage); - unsigned long priv; - unsigned int f, from = offset_in_thp(page, pos); - unsigned int t, to = from + copied; - loff_t i_size, write_end_pos; - - _enter("{%llx:%llu},{%lx}", - vnode->fid.vid, vnode->fid.vnode, page->index); - - len = min_t(size_t, len, thp_size(page) - from); - if (!PageUptodate(page)) { - if (copied < len) { - copied = 0; - goto out; - } - - SetPageUptodate(page); - } - - if (copied == 0) - goto out; - - write_end_pos = pos + copied; - - i_size = i_size_read(&vnode->vfs_inode); - if (write_end_pos > i_size) { - write_seqlock(&vnode->cb_lock); - i_size = i_size_read(&vnode->vfs_inode); - if (write_end_pos > i_size) - i_size_write(&vnode->vfs_inode, write_end_pos); - write_sequnlock(&vnode->cb_lock); - fscache_update_cookie(afs_vnode_cache(vnode), NULL, &write_end_pos); - } - - if (PagePrivate(page)) { - priv = page_private(page); - f = afs_page_dirty_from(page, priv); - t = afs_page_dirty_to(page, priv); - if (from < f) - f = from; - if (to > t) - t = to; - priv = afs_page_dirty(page, f, t); - set_page_private(page, priv); - trace_afs_page_dirty(vnode, tracepoint_string("dirty+"), page); - } else { - priv = afs_page_dirty(page, from, to); - attach_page_private(page, (void *)priv); - trace_afs_page_dirty(vnode, tracepoint_string("dirty"), page); - } - - if (set_page_dirty(page)) - _debug("dirtied %lx", page->index); - -out: - unlock_page(page); - put_page(page); - return copied; -} - /* * kill all the pages in the given range */ @@ -812,26 +666,6 @@ int afs_writepages(struct address_space *mapping, return ret; } -/* - * write to an AFS file - */ -ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from) -{ - struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp)); - size_t count = iov_iter_count(from); - - _enter("{%llx:%llu},{%zu},", - vnode->fid.vid, vnode->fid.vnode, count); - - if (IS_SWAPFILE(&vnode->vfs_inode)) { - printk(KERN_INFO - "AFS: Attempt to write to active swap file!\n"); - return -EBUSY; - } - - return generic_file_write_iter(iocb, from); -} - /* * flush any dirty pages for this process, and check for write errors. * - the return status from this call provides a reliable indication of diff --git a/fs/netfs/Makefile b/fs/netfs/Makefile index c15bfc966d96..3e11453ad2c5 100644 --- a/fs/netfs/Makefile +++ b/fs/netfs/Makefile @@ -1,5 +1,11 @@ # SPDX-License-Identifier: GPL-2.0 -netfs-y := read_helper.o stats.o +netfs-y := \ + objects.o \ + read_helper.o \ + write_helper.o +# dio_helper.o + +netfs-$(CONFIG_NETFS_STATS) += stats.o obj-$(CONFIG_NETFS_SUPPORT) := netfs.o diff --git a/fs/netfs/dio_helper.c b/fs/netfs/dio_helper.c new file mode 100644 index 000000000000..3072de344601 --- /dev/null +++ b/fs/netfs/dio_helper.c @@ -0,0 +1,140 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Network filesystem high-level DIO support. + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include "internal.h" +#include + +/* + * Perform a direct I/O write to a netfs server. + */ +ssize_t netfs_file_direct_write(struct netfs_dirty_region *region, + struct kiocb *iocb, struct iov_iter *from) +{ + struct file *file = iocb->ki_filp; + struct address_space *mapping = file->f_mapping; + struct inode *inode = mapping->host; + loff_t pos = iocb->ki_pos, last; + ssize_t written; + size_t write_len; + pgoff_t end; + int ret; + + write_len = iov_iter_count(from); + last = pos + write_len - 1; + end = to >> PAGE_SHIFT; + + if (iocb->ki_flags & IOCB_NOWAIT) { + /* If there are pages to writeback, return */ + if (filemap_range_has_page(file->f_mapping, pos, last)) + return -EAGAIN; + } else { + ret = filemap_write_and_wait_range(mapping, pos, last); + if (ret) + return ret; + } + + /* After a write we want buffered reads to be sure to go to disk to get + * the new data. We invalidate clean cached page from the region we're + * about to write. We do this *before* the write so that we can return + * without clobbering -EIOCBQUEUED from ->direct_IO(). + */ + ret = invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT, end); + if (ret) { + /* If the page can't be invalidated, return 0 to fall back to + * buffered write. + */ + return ret == -EBUSY ? 0 : ret; + } + + written = mapping->a_ops->direct_IO(iocb, from); + + /* Finally, try again to invalidate clean pages which might have been + * cached by non-direct readahead, or faulted in by get_user_pages() + * if the source of the write was an mmap'ed region of the file + * we're writing. Either one is a pretty crazy thing to do, + * so we don't support it 100%. If this invalidation + * fails, tough, the write still worked... + * + * Most of the time we do not need this since dio_complete() will do + * the invalidation for us. However there are some file systems that + * do not end up with dio_complete() being called, so let's not break + * them by removing it completely. + * + * Noticeable example is a blkdev_direct_IO(). + * + * Skip invalidation for async writes or if mapping has no pages. + */ + if (written > 0 && mapping->nrpages && + invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT, end)) + dio_warn_stale_pagecache(file); + + if (written > 0) { + pos += written; + write_len -= written; + if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { + i_size_write(inode, pos); + mark_inode_dirty(inode); + } + iocb->ki_pos = pos; + } + if (written != -EIOCBQUEUED) + iov_iter_revert(from, write_len - iov_iter_count(from)); +out: +#if 0 + /* + * If the write stopped short of completing, fall back to + * buffered writes. Some filesystems do this for writes to + * holes, for example. For DAX files, a buffered write will + * not succeed (even if it did, DAX does not handle dirty + * page-cache pages correctly). + */ + if (written < 0 || !iov_iter_count(from) || IS_DAX(inode)) + goto out; + + status = netfs_perform_write(region, file, from, pos = iocb->ki_pos); + /* + * If generic_perform_write() returned a synchronous error + * then we want to return the number of bytes which were + * direct-written, or the error code if that was zero. Note + * that this differs from normal direct-io semantics, which + * will return -EFOO even if some bytes were written. + */ + if (unlikely(status < 0)) { + err = status; + goto out; + } + /* + * We need to ensure that the page cache pages are written to + * disk and invalidated to preserve the expected O_DIRECT + * semantics. + */ + endbyte = pos + status - 1; + err = filemap_write_and_wait_range(mapping, pos, endbyte); + if (err == 0) { + iocb->ki_pos = endbyte + 1; + written += status; + invalidate_mapping_pages(mapping, + pos >> PAGE_SHIFT, + endbyte >> PAGE_SHIFT); + } else { + /* + * We don't know how much we wrote, so just return + * the number of bytes which were direct-written + */ + } +#endif + return written; +} diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h index 4805d9fc8808..77ceab694348 100644 --- a/fs/netfs/internal.h +++ b/fs/netfs/internal.h @@ -15,11 +15,41 @@ #define pr_fmt(fmt) "netfs: " fmt +/* + * dio_helper.c + */ +ssize_t netfs_file_direct_write(struct netfs_dirty_region *region, + struct kiocb *iocb, struct iov_iter *from); + +/* + * objects.c + */ +struct netfs_flush_group *netfs_get_flush_group(struct netfs_flush_group *group); +void netfs_put_flush_group(struct netfs_flush_group *group); +struct netfs_dirty_region *netfs_alloc_dirty_region(void); +struct netfs_dirty_region *netfs_get_dirty_region(struct netfs_i_context *ctx, + struct netfs_dirty_region *region, + enum netfs_region_trace what); +void netfs_free_dirty_region(struct netfs_i_context *ctx, struct netfs_dirty_region *region); +void netfs_put_dirty_region(struct netfs_i_context *ctx, + struct netfs_dirty_region *region, + enum netfs_region_trace what); + /* * read_helper.c */ extern unsigned int netfs_debug; +int netfs_prefetch_for_write(struct file *file, struct page *page, loff_t pos, size_t len, + bool always_fill); + +/* + * write_helper.c + */ +void netfs_flush_region(struct netfs_i_context *ctx, + struct netfs_dirty_region *region, + enum netfs_dirty_trace why); + /* * stats.c */ @@ -42,6 +72,8 @@ extern atomic_t netfs_n_rh_write_begin; extern atomic_t netfs_n_rh_write_done; extern atomic_t netfs_n_rh_write_failed; extern atomic_t netfs_n_rh_write_zskip; +extern atomic_t netfs_n_wh_region; +extern atomic_t netfs_n_wh_flush_group; static inline void netfs_stat(atomic_t *stat) diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c new file mode 100644 index 000000000000..ba1e052aa352 --- /dev/null +++ b/fs/netfs/objects.c @@ -0,0 +1,113 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Object lifetime handling and tracing. + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include +#include +#include +#include +#include +#include +#include "internal.h" + +/** + * netfs_new_flush_group - Create a new write flush group + * @inode: The inode for which this is a flush group. + * @netfs_priv: Netfs private data to include in the new group + * + * Create a new flush group and add it to the tail of the inode's group list. + * Flush groups are used to control the order in which dirty data is written + * back to the server. + * + * The caller must hold ctx->lock. + */ +struct netfs_flush_group *netfs_new_flush_group(struct inode *inode, void *netfs_priv) +{ + struct netfs_flush_group *group; + struct netfs_i_context *ctx = netfs_i_context(inode); + + group = kzalloc(sizeof(*group), GFP_KERNEL); + if (group) { + group->netfs_priv = netfs_priv; + INIT_LIST_HEAD(&group->region_list); + refcount_set(&group->ref, 1); + netfs_stat(&netfs_n_wh_flush_group); + list_add_tail(&group->group_link, &ctx->flush_groups); + } + return group; +} +EXPORT_SYMBOL(netfs_new_flush_group); + +struct netfs_flush_group *netfs_get_flush_group(struct netfs_flush_group *group) +{ + refcount_inc(&group->ref); + return group; +} + +void netfs_put_flush_group(struct netfs_flush_group *group) +{ + if (group && refcount_dec_and_test(&group->ref)) { + netfs_stat_d(&netfs_n_wh_flush_group); + kfree(group); + } +} + +struct netfs_dirty_region *netfs_alloc_dirty_region(void) +{ + struct netfs_dirty_region *region; + + region = kzalloc(sizeof(struct netfs_dirty_region), GFP_KERNEL); + if (region) + netfs_stat(&netfs_n_wh_region); + return region; +} + +struct netfs_dirty_region *netfs_get_dirty_region(struct netfs_i_context *ctx, + struct netfs_dirty_region *region, + enum netfs_region_trace what) +{ + int ref; + + __refcount_inc(®ion->ref, &ref); + trace_netfs_ref_region(region->debug_id, ref + 1, what); + return region; +} + +void netfs_free_dirty_region(struct netfs_i_context *ctx, + struct netfs_dirty_region *region) +{ + if (region) { + trace_netfs_ref_region(region->debug_id, 0, netfs_region_trace_free); + if (ctx->ops->free_dirty_region) + ctx->ops->free_dirty_region(region); + netfs_put_flush_group(region->group); + netfs_stat_d(&netfs_n_wh_region); + kfree(region); + } +} + +void netfs_put_dirty_region(struct netfs_i_context *ctx, + struct netfs_dirty_region *region, + enum netfs_region_trace what) +{ + bool dead; + int ref; + + if (!region) + return; + dead = __refcount_dec_and_test(®ion->ref, &ref); + trace_netfs_ref_region(region->debug_id, ref - 1, what); + if (dead) { + if (!list_empty(®ion->active_link) || + !list_empty(®ion->dirty_link)) { + spin_lock(&ctx->lock); + list_del_init(®ion->active_link); + list_del_init(®ion->dirty_link); + spin_unlock(&ctx->lock); + } + netfs_free_dirty_region(ctx, region); + } +} diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c index aa98ecf6df6b..bfcdbbd32f4c 100644 --- a/fs/netfs/read_helper.c +++ b/fs/netfs/read_helper.c @@ -1321,3 +1321,97 @@ int netfs_write_begin(struct file *file, struct address_space *mapping, return ret; } EXPORT_SYMBOL(netfs_write_begin); + +/* + * Preload the data into a page we're proposing to write into. + */ +int netfs_prefetch_for_write(struct file *file, struct page *page, + loff_t pos, size_t len, bool always_fill) +{ + struct address_space *mapping = page_file_mapping(page); + struct netfs_read_request *rreq; + struct netfs_i_context *ctx = netfs_i_context(mapping->host); + struct page *xpage; + unsigned int debug_index = 0; + int ret; + + DEFINE_READAHEAD(ractl, file, NULL, mapping, page_index(page)); + + /* If the page is beyond the EOF, we want to clear it - unless it's + * within the cache granule containing the EOF, in which case we need + * to preload the granule. + */ + if (!netfs_is_cache_enabled(mapping->host)) { + if (netfs_skip_page_read(page, pos, len, always_fill)) { + netfs_stat(&netfs_n_rh_write_zskip); + ret = 0; + goto error; + } + } + + ret = -ENOMEM; + rreq = netfs_alloc_read_request(mapping, file); + if (!rreq) + goto error; + rreq->start = page_offset(page); + rreq->len = thp_size(page); + rreq->no_unlock_page = page_file_offset(page); + __set_bit(NETFS_RREQ_NO_UNLOCK_PAGE, &rreq->flags); + + if (ctx->ops->begin_cache_operation) { + ret = ctx->ops->begin_cache_operation(rreq); + if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) + goto error_put; + } + + netfs_stat(&netfs_n_rh_write_begin); + trace_netfs_read(rreq, pos, len, netfs_read_trace_prefetch_for_write); + + /* Expand the request to meet caching requirements and download + * preferences. + */ + ractl._nr_pages = thp_nr_pages(page); + netfs_rreq_expand(rreq, &ractl); + + /* Set up the output buffer */ + ret = netfs_rreq_set_up_buffer(rreq, &ractl, page, + readahead_index(&ractl), readahead_count(&ractl)); + if (ret < 0) { + while ((xpage = readahead_page(&ractl))) + if (xpage != page) + put_page(xpage); + goto error_put; + } + + netfs_get_read_request(rreq); + atomic_set(&rreq->nr_rd_ops, 1); + do { + if (!netfs_rreq_submit_slice(rreq, &debug_index)) + break; + + } while (rreq->submitted < rreq->len); + + /* Keep nr_rd_ops incremented so that the ref always belongs to us, and + * the service code isn't punted off to a random thread pool to + * process. + */ + for (;;) { + wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1); + netfs_rreq_assess(rreq, false); + if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags)) + break; + cond_resched(); + } + + ret = rreq->error; + if (ret == 0 && rreq->submitted < rreq->len) { + trace_netfs_failure(rreq, NULL, ret, netfs_fail_short_write_begin); + ret = -EIO; + } + +error_put: + netfs_put_read_request(rreq, false); +error: + _leave(" = %d", ret); + return ret; +} diff --git a/fs/netfs/stats.c b/fs/netfs/stats.c index 5510a7a14a40..7c079ca47b5b 100644 --- a/fs/netfs/stats.c +++ b/fs/netfs/stats.c @@ -27,6 +27,8 @@ atomic_t netfs_n_rh_write_begin; atomic_t netfs_n_rh_write_done; atomic_t netfs_n_rh_write_failed; atomic_t netfs_n_rh_write_zskip; +atomic_t netfs_n_wh_region; +atomic_t netfs_n_wh_flush_group; void netfs_stats_show(struct seq_file *m) { @@ -54,5 +56,8 @@ void netfs_stats_show(struct seq_file *m) atomic_read(&netfs_n_rh_write), atomic_read(&netfs_n_rh_write_done), atomic_read(&netfs_n_rh_write_failed)); + seq_printf(m, "WrHelp : R=%u F=%u\n", + atomic_read(&netfs_n_wh_region), + atomic_read(&netfs_n_wh_flush_group)); } EXPORT_SYMBOL(netfs_stats_show); diff --git a/fs/netfs/write_helper.c b/fs/netfs/write_helper.c new file mode 100644 index 000000000000..a8c58eaa84d0 --- /dev/null +++ b/fs/netfs/write_helper.c @@ -0,0 +1,908 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Network filesystem high-level write support. + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include +#include +#include +#include +#include +#include +#include "internal.h" + +static atomic_t netfs_region_debug_ids; + +static bool __overlaps(loff_t start1, loff_t end1, loff_t start2, loff_t end2) +{ + return (start1 < start2) ? end1 > start2 : end2 > start1; +} + +static bool overlaps(struct netfs_range *a, struct netfs_range *b) +{ + return __overlaps(a->start, a->end, b->start, b->end); +} + +static int wait_on_region(struct netfs_dirty_region *region, + enum netfs_region_state state) +{ + return wait_var_event_interruptible(®ion->state, + READ_ONCE(region->state) >= state); +} + +/* + * Grab a page for writing. We don't lock it at this point as we have yet to + * preemptively trigger a fault-in - but we need to know how large the page + * will be before we try that. + */ +static struct page *netfs_grab_page_for_write(struct address_space *mapping, + loff_t pos, size_t len_remaining) +{ + struct page *page; + int fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT; + + page = pagecache_get_page(mapping, pos >> PAGE_SHIFT, fgp_flags, + mapping_gfp_mask(mapping)); + if (!page) + return ERR_PTR(-ENOMEM); + wait_for_stable_page(page); + return page; +} + +/* + * Initialise a new dirty page group. The caller is responsible for setting + * the type and any flags that they want. + */ +static void netfs_init_dirty_region(struct netfs_dirty_region *region, + struct inode *inode, struct file *file, + enum netfs_region_type type, + unsigned long flags, + loff_t start, loff_t end) +{ + struct netfs_flush_group *group; + struct netfs_i_context *ctx = netfs_i_context(inode); + + region->state = NETFS_REGION_IS_PENDING; + region->type = type; + region->flags = flags; + region->reserved.start = start; + region->reserved.end = end; + region->dirty.start = start; + region->dirty.end = start; + region->bounds.start = round_down(start, ctx->bsize); + region->bounds.end = round_up(end, ctx->bsize); + region->i_size = i_size_read(inode); + region->debug_id = atomic_inc_return(&netfs_region_debug_ids); + INIT_LIST_HEAD(®ion->active_link); + INIT_LIST_HEAD(®ion->dirty_link); + INIT_LIST_HEAD(®ion->flush_link); + refcount_set(®ion->ref, 1); + spin_lock_init(®ion->lock); + if (file && ctx->ops->init_dirty_region) + ctx->ops->init_dirty_region(region, file); + if (!region->group) { + group = list_last_entry(&ctx->flush_groups, + struct netfs_flush_group, group_link); + region->group = netfs_get_flush_group(group); + list_add_tail(®ion->flush_link, &group->region_list); + } + trace_netfs_ref_region(region->debug_id, 1, netfs_region_trace_new); + trace_netfs_dirty(ctx, region, NULL, netfs_dirty_trace_new); +} + +/* + * Queue a region for flushing. Regions may need to be flushed in the right + * order (e.g. ceph snaps) and so we may need to chuck other regions onto the + * flush queue first. + * + * The caller must hold ctx->lock. + */ +void netfs_flush_region(struct netfs_i_context *ctx, + struct netfs_dirty_region *region, + enum netfs_dirty_trace why) +{ + struct netfs_flush_group *group; + + LIST_HEAD(flush_queue); + + kenter("%x", region->debug_id); + + if (test_bit(NETFS_REGION_FLUSH_Q, ®ion->flags) || + region->group->flush) + return; + + trace_netfs_dirty(ctx, region, NULL, why); + + /* If the region isn't in the bottom flush group, we need to flush out + * all of the flush groups below it. + */ + while (!list_is_first(®ion->group->group_link, &ctx->flush_groups)) { + group = list_first_entry(&ctx->flush_groups, + struct netfs_flush_group, group_link); + group->flush = true; + list_del_init(&group->group_link); + list_splice_tail_init(&group->region_list, &ctx->flush_queue); + netfs_put_flush_group(group); + } + + set_bit(NETFS_REGION_FLUSH_Q, ®ion->flags); + list_move_tail(®ion->flush_link, &ctx->flush_queue); +} + +/* + * Decide if/how a write can be merged with a dirty region. + */ +static enum netfs_write_compatibility netfs_write_compatibility( + struct netfs_i_context *ctx, + struct netfs_dirty_region *old, + struct netfs_dirty_region *candidate) +{ + if (old->type == NETFS_REGION_DIO || + old->type == NETFS_REGION_DSYNC || + old->state >= NETFS_REGION_IS_FLUSHING || + /* The bounding boxes of DSYNC writes can overlap with those of + * other DSYNC writes and ordinary writes. + */ + candidate->group != old->group || + old->group->flush) + return NETFS_WRITES_INCOMPATIBLE; + if (!ctx->ops->is_write_compatible) { + if (candidate->type == NETFS_REGION_DSYNC) + return NETFS_WRITES_SUPERSEDE; + return NETFS_WRITES_COMPATIBLE; + } + return ctx->ops->is_write_compatible(ctx, old, candidate); +} + +/* + * Split a dirty region. + */ +static struct netfs_dirty_region *netfs_split_dirty_region( + struct netfs_i_context *ctx, + struct netfs_dirty_region *region, + struct netfs_dirty_region **spare, + unsigned long long pos) +{ + struct netfs_dirty_region *tail = *spare; + + *spare = NULL; + *tail = *region; + region->dirty.end = pos; + tail->dirty.start = pos; + tail->debug_id = atomic_inc_return(&netfs_region_debug_ids); + + refcount_set(&tail->ref, 1); + INIT_LIST_HEAD(&tail->active_link); + netfs_get_flush_group(tail->group); + spin_lock_init(&tail->lock); + // TODO: grab cache resources + + // need to split the bounding box? + __set_bit(NETFS_REGION_SUPERSEDED, &tail->flags); + if (ctx->ops->split_dirty_region) + ctx->ops->split_dirty_region(tail); + list_add(&tail->dirty_link, ®ion->dirty_link); + list_add(&tail->flush_link, ®ion->flush_link); + trace_netfs_dirty(ctx, tail, region, netfs_dirty_trace_split); + return tail; +} + +/* + * Queue a write for access to the pagecache. The caller must hold ctx->lock. + * The NETFS_REGION_PENDING flag will be cleared when it's possible to proceed. + */ +static void netfs_queue_write(struct netfs_i_context *ctx, + struct netfs_dirty_region *candidate) +{ + struct netfs_dirty_region *r; + struct list_head *p; + + /* We must wait for any overlapping pending writes */ + list_for_each_entry(r, &ctx->pending_writes, active_link) { + if (overlaps(&candidate->bounds, &r->bounds)) { + if (overlaps(&candidate->reserved, &r->reserved) || + netfs_write_compatibility(ctx, r, candidate) == + NETFS_WRITES_INCOMPATIBLE) + goto add_to_pending_queue; + } + } + + /* We mustn't let the request overlap with the reservation of any other + * active writes, though it can overlap with a bounding box if the + * writes are compatible. + */ + list_for_each(p, &ctx->active_writes) { + r = list_entry(p, struct netfs_dirty_region, active_link); + if (r->bounds.end <= candidate->bounds.start) + continue; + if (r->bounds.start >= candidate->bounds.end) + break; + if (overlaps(&candidate->bounds, &r->bounds)) { + if (overlaps(&candidate->reserved, &r->reserved) || + netfs_write_compatibility(ctx, r, candidate) == + NETFS_WRITES_INCOMPATIBLE) + goto add_to_pending_queue; + } + } + + /* We can install the record in the active list to reserve our slot */ + list_add(&candidate->active_link, p); + + /* Okay, we've reserved our slot in the active queue */ + smp_store_release(&candidate->state, NETFS_REGION_IS_RESERVED); + trace_netfs_dirty(ctx, candidate, NULL, netfs_dirty_trace_reserved); + wake_up_var(&candidate->state); + kleave(" [go]"); + return; + +add_to_pending_queue: + /* We get added to the pending list and then we have to wait */ + list_add(&candidate->active_link, &ctx->pending_writes); + trace_netfs_dirty(ctx, candidate, NULL, netfs_dirty_trace_wait_pend); + kleave(" [wait pend]"); +} + +/* + * Make sure there's a flush group. + */ +static int netfs_require_flush_group(struct inode *inode) +{ + struct netfs_flush_group *group; + struct netfs_i_context *ctx = netfs_i_context(inode); + + if (list_empty(&ctx->flush_groups)) { + kdebug("new flush group"); + group = netfs_new_flush_group(inode, NULL); + if (!group) + return -ENOMEM; + } + return 0; +} + +/* + * Create a dirty region record for the write we're about to do and add it to + * the list of regions. We may need to wait for conflicting writes to + * complete. + */ +static struct netfs_dirty_region *netfs_prepare_region(struct inode *inode, + struct file *file, + loff_t start, size_t len, + enum netfs_region_type type, + unsigned long flags) +{ + struct netfs_dirty_region *candidate; + struct netfs_i_context *ctx = netfs_i_context(inode); + loff_t end = start + len; + int ret; + + ret = netfs_require_flush_group(inode); + if (ret < 0) + return ERR_PTR(ret); + + candidate = netfs_alloc_dirty_region(); + if (!candidate) + return ERR_PTR(-ENOMEM); + + netfs_init_dirty_region(candidate, inode, file, type, flags, start, end); + + spin_lock(&ctx->lock); + netfs_queue_write(ctx, candidate); + spin_unlock(&ctx->lock); + return candidate; +} + +/* + * Activate a write. This adds it to the dirty list and does any necessary + * flushing and superceding there. The caller must provide a spare region + * record so that we can split a dirty record if we need to supersede it. + */ +static void __netfs_activate_write(struct netfs_i_context *ctx, + struct netfs_dirty_region *candidate, + struct netfs_dirty_region **spare) +{ + struct netfs_dirty_region *r; + struct list_head *p; + enum netfs_write_compatibility comp; + bool conflicts = false; + + /* See if there are any dirty regions that need flushing first. */ + list_for_each(p, &ctx->dirty_regions) { + r = list_entry(p, struct netfs_dirty_region, dirty_link); + if (r->bounds.end <= candidate->bounds.start) + continue; + if (r->bounds.start >= candidate->bounds.end) + break; + + if (list_empty(&candidate->dirty_link) && + r->dirty.start > candidate->dirty.start) + list_add_tail(&candidate->dirty_link, p); + + comp = netfs_write_compatibility(ctx, r, candidate); + switch (comp) { + case NETFS_WRITES_INCOMPATIBLE: + netfs_flush_region(ctx, r, netfs_dirty_trace_flush_conflict); + conflicts = true; + continue; + + case NETFS_WRITES_SUPERSEDE: + if (!overlaps(&candidate->reserved, &r->dirty)) + continue; + if (r->dirty.start < candidate->dirty.start) { + /* The region overlaps the beginning of our + * region, we split it and mark the overlapping + * part as superseded. We insert ourself + * between. + */ + r = netfs_split_dirty_region(ctx, r, spare, + candidate->reserved.start); + list_add_tail(&candidate->dirty_link, &r->dirty_link); + p = &r->dirty_link; /* Advance the for-loop */ + } else { + /* The region is after ours, so make sure we're + * inserted before it. + */ + if (list_empty(&candidate->dirty_link)) + list_add_tail(&candidate->dirty_link, &r->dirty_link); + set_bit(NETFS_REGION_SUPERSEDED, &r->flags); + trace_netfs_dirty(ctx, candidate, r, netfs_dirty_trace_supersedes); + } + continue; + + case NETFS_WRITES_COMPATIBLE: + continue; + } + } + + if (list_empty(&candidate->dirty_link)) + list_add_tail(&candidate->dirty_link, p); + netfs_get_dirty_region(ctx, candidate, netfs_region_trace_get_dirty); + + if (conflicts) { + /* The caller must wait for the flushes to complete. */ + trace_netfs_dirty(ctx, candidate, NULL, netfs_dirty_trace_wait_active); + kleave(" [wait flush]"); + return; + } + + /* Okay, we're cleared to proceed. */ + smp_store_release(&candidate->state, NETFS_REGION_IS_ACTIVE); + trace_netfs_dirty(ctx, candidate, NULL, netfs_dirty_trace_active); + wake_up_var(&candidate->state); + kleave(" [go]"); + return; +} + +static int netfs_activate_write(struct netfs_i_context *ctx, + struct netfs_dirty_region *region) +{ + struct netfs_dirty_region *spare; + + spare = netfs_alloc_dirty_region(); + if (!spare) + return -ENOMEM; + + spin_lock(&ctx->lock); + __netfs_activate_write(ctx, region, &spare); + spin_unlock(&ctx->lock); + netfs_free_dirty_region(ctx, spare); + return 0; +} + +/* + * Merge a completed active write into the list of dirty regions. The region + * can be in one of a number of states: + * + * - Ordinary write, error, no data copied. Discard. + * - Ordinary write, unflushed. Dirty + * - Ordinary write, flush started. Dirty + * - Ordinary write, completed/failed. Discard. + * - DIO write, completed/failed. Discard. + * - DSYNC write, error before flush. As ordinary. + * - DSYNC write, flushed in progress, EINTR. Dirty (supersede). + * - DSYNC write, written to server and cache. Dirty (supersede)/Discard. + * - DSYNC write, written to server but not yet cache. Dirty. + * + * Once we've dealt with this record, we see about activating some other writes + * to fill the activity hole. + * + * This eats the caller's ref on the region. + */ +static void netfs_merge_dirty_region(struct netfs_i_context *ctx, + struct netfs_dirty_region *region) +{ + struct netfs_dirty_region *p, *q, *front; + bool new_content = test_bit(NETFS_ICTX_NEW_CONTENT, &ctx->flags); + LIST_HEAD(graveyard); + + list_del_init(®ion->active_link); + + switch (region->type) { + case NETFS_REGION_DIO: + list_move_tail(®ion->dirty_link, &graveyard); + goto discard; + + case NETFS_REGION_DSYNC: + /* A DSYNC write may have overwritten some dirty data + * and caused the writeback of other dirty data. + */ + goto scan_forwards; + + case NETFS_REGION_ORDINARY: + if (region->dirty.end == region->dirty.start) { + list_move_tail(®ion->dirty_link, &graveyard); + goto discard; + } + goto scan_backwards; + } + +scan_backwards: + kdebug("scan_backwards"); + /* Search backwards for a preceding record that we might be able to + * merge with. We skip over any intervening flush-in-progress records. + */ + p = front = region; + list_for_each_entry_continue_reverse(p, &ctx->dirty_regions, dirty_link) { + kdebug("- back %x", p->debug_id); + if (p->state >= NETFS_REGION_IS_FLUSHING) + continue; + if (p->state == NETFS_REGION_IS_ACTIVE) + break; + if (p->bounds.end < region->bounds.start) + break; + if (p->dirty.end >= region->dirty.start || new_content) + goto merge_backwards; + } + goto scan_forwards; + +merge_backwards: + kdebug("merge_backwards"); + if (test_bit(NETFS_REGION_SUPERSEDED, &p->flags) || + netfs_write_compatibility(ctx, p, region) != NETFS_WRITES_COMPATIBLE) + goto scan_forwards; + + front = p; + front->bounds.end = max(front->bounds.end, region->bounds.end); + front->dirty.end = max(front->dirty.end, region->dirty.end); + set_bit(NETFS_REGION_SUPERSEDED, ®ion->flags); + list_del_init(®ion->flush_link); + trace_netfs_dirty(ctx, front, region, netfs_dirty_trace_merged_back); + +scan_forwards: + /* Subsume forwards any records this one covers. There should be no + * non-supersedeable incompatible regions in our range as we would have + * flushed and waited for them before permitting this write to start. + * + * There can, however, be regions undergoing flushing which we need to + * skip over and not merge with. + */ + kdebug("scan_forwards"); + p = region; + list_for_each_entry_safe_continue(p, q, &ctx->dirty_regions, dirty_link) { + kdebug("- forw %x", p->debug_id); + if (p->state >= NETFS_REGION_IS_FLUSHING) + continue; + if (p->state == NETFS_REGION_IS_ACTIVE) + break; + if (p->dirty.start > region->dirty.end && + (!new_content || p->bounds.start > p->bounds.end)) + break; + + if (region->dirty.end >= p->dirty.end) { + /* Entirely subsumed */ + list_move_tail(&p->dirty_link, &graveyard); + list_del_init(&p->flush_link); + trace_netfs_dirty(ctx, front, p, netfs_dirty_trace_merged_sub); + continue; + } + + goto merge_forwards; + } + goto merge_complete; + +merge_forwards: + kdebug("merge_forwards"); + if (test_bit(NETFS_REGION_SUPERSEDED, &p->flags) || + netfs_write_compatibility(ctx, p, front) == NETFS_WRITES_SUPERSEDE) { + /* If a region was partially superseded by us, we need to roll + * it forwards and remove the superseded flag. + */ + if (p->dirty.start < front->dirty.end) { + p->dirty.start = front->dirty.end; + clear_bit(NETFS_REGION_SUPERSEDED, &p->flags); + } + trace_netfs_dirty(ctx, p, front, netfs_dirty_trace_superseded); + goto merge_complete; + } + + /* Simply merge overlapping/contiguous ordinary areas together. */ + front->bounds.end = max(front->bounds.end, p->bounds.end); + front->dirty.end = max(front->dirty.end, p->dirty.end); + list_move_tail(&p->dirty_link, &graveyard); + list_del_init(&p->flush_link); + trace_netfs_dirty(ctx, front, p, netfs_dirty_trace_merged_forw); + +merge_complete: + if (test_bit(NETFS_REGION_SUPERSEDED, ®ion->flags)) { + list_move_tail(®ion->dirty_link, &graveyard); + } +discard: + while (!list_empty(&graveyard)) { + p = list_first_entry(&graveyard, struct netfs_dirty_region, dirty_link); + list_del_init(&p->dirty_link); + smp_store_release(&p->state, NETFS_REGION_IS_COMPLETE); + trace_netfs_dirty(ctx, p, NULL, netfs_dirty_trace_complete); + wake_up_var(&p->state); + netfs_put_dirty_region(ctx, p, netfs_region_trace_put_merged); + } +} + +/* + * Start pending writes in a window we've created by the removal of an active + * write. The writes are bundled onto the given queue and it's left as an + * exercise for the caller to actually start them. + */ +static void netfs_start_pending_writes(struct netfs_i_context *ctx, + struct list_head *prev_p, + struct list_head *queue) +{ + struct netfs_dirty_region *prev = NULL, *next = NULL, *p, *q; + struct netfs_range window = { 0, ULLONG_MAX }; + + if (prev_p != &ctx->active_writes) { + prev = list_entry(prev_p, struct netfs_dirty_region, active_link); + window.start = prev->reserved.end; + if (!list_is_last(prev_p, &ctx->active_writes)) { + next = list_next_entry(prev, active_link); + window.end = next->reserved.start; + } + } else if (!list_empty(&ctx->active_writes)) { + next = list_last_entry(&ctx->active_writes, + struct netfs_dirty_region, active_link); + window.end = next->reserved.start; + } + + list_for_each_entry_safe(p, q, &ctx->pending_writes, active_link) { + bool skip = false; + + if (!overlaps(&p->reserved, &window)) + continue; + + /* Narrow the window when we find a region that requires more + * than we can immediately provide. The queue is in submission + * order and we need to prevent starvation. + */ + if (p->type == NETFS_REGION_DIO) { + if (p->bounds.start < window.start) { + window.start = p->bounds.start; + skip = true; + } + if (p->bounds.end > window.end) { + window.end = p->bounds.end; + skip = true; + } + } else { + if (p->reserved.start < window.start) { + window.start = p->reserved.start; + skip = true; + } + if (p->reserved.end > window.end) { + window.end = p->reserved.end; + skip = true; + } + } + if (window.start >= window.end) + break; + if (skip) + continue; + + /* Okay, we have a gap that's large enough to start this write + * in. Make sure it's compatible with any region its bounds + * overlap. + */ + if (prev && + p->bounds.start < prev->bounds.end && + netfs_write_compatibility(ctx, prev, p) == NETFS_WRITES_INCOMPATIBLE) { + window.start = max(window.start, p->bounds.end); + skip = true; + } + + if (next && + p->bounds.end > next->bounds.start && + netfs_write_compatibility(ctx, next, p) == NETFS_WRITES_INCOMPATIBLE) { + window.end = min(window.end, p->bounds.start); + skip = true; + } + if (window.start >= window.end) + break; + if (skip) + continue; + + /* Okay, we can start this write. */ + trace_netfs_dirty(ctx, p, NULL, netfs_dirty_trace_start_pending); + list_move(&p->active_link, + prev ? &prev->active_link : &ctx->pending_writes); + list_add_tail(&p->dirty_link, queue); + if (p->type == NETFS_REGION_DIO) + window.start = p->bounds.end; + else + window.start = p->reserved.end; + prev = p; + } +} + +/* + * We completed the modification phase of a write. We need to fix up the dirty + * list, remove this region from the active list and start waiters. + */ +static void netfs_commit_write(struct netfs_i_context *ctx, + struct netfs_dirty_region *region) +{ + struct netfs_dirty_region *p; + struct list_head *prev; + LIST_HEAD(queue); + + spin_lock(&ctx->lock); + smp_store_release(®ion->state, NETFS_REGION_IS_DIRTY); + trace_netfs_dirty(ctx, region, NULL, netfs_dirty_trace_commit); + wake_up_var(®ion->state); + + prev = region->active_link.prev; + netfs_merge_dirty_region(ctx, region); + if (!list_empty(&ctx->pending_writes)) + netfs_start_pending_writes(ctx, prev, &queue); + spin_unlock(&ctx->lock); + + while (!list_empty(&queue)) { + p = list_first_entry(&queue, struct netfs_dirty_region, dirty_link); + list_del_init(&p->dirty_link); + smp_store_release(&p->state, NETFS_REGION_IS_DIRTY); + wake_up_var(&p->state); + } +} + +/* + * Write data into a prereserved region of the pagecache attached to a netfs + * inode. + */ +static ssize_t netfs_perform_write(struct netfs_dirty_region *region, + struct kiocb *iocb, struct iov_iter *i) +{ + struct file *file = iocb->ki_filp; + struct netfs_i_context *ctx = netfs_i_context(file_inode(file)); + struct page *page; + ssize_t written = 0, ret; + loff_t new_pos, i_size; + bool always_fill = false; + + do { + size_t plen; + size_t offset; /* Offset into pagecache page */ + size_t bytes; /* Bytes to write to page */ + size_t copied; /* Bytes copied from user */ + bool relock = false; + + page = netfs_grab_page_for_write(file->f_mapping, region->dirty.end, + iov_iter_count(i)); + if (!page) + return -ENOMEM; + + plen = thp_size(page); + offset = region->dirty.end - page_file_offset(page); + bytes = min_t(size_t, plen - offset, iov_iter_count(i)); + + kdebug("segment %zx @%zx", bytes, offset); + + if (!PageUptodate(page)) { + unlock_page(page); /* Avoid deadlocking fault-in */ + relock = true; + } + + /* Bring in the user page that we will copy from _first_. + * Otherwise there's a nasty deadlock on copying from the + * same page as we're writing to, without it being marked + * up-to-date. + * + * Not only is this an optimisation, but it is also required + * to check that the address is actually valid, when atomic + * usercopies are used, below. + */ + if (unlikely(iov_iter_fault_in_readable(i, bytes))) { + kdebug("fault-in"); + ret = -EFAULT; + goto error_page; + } + + if (fatal_signal_pending(current)) { + ret = -EINTR; + goto error_page; + } + + if (relock) { + ret = lock_page_killable(page); + if (ret < 0) + goto error_page; + } + +redo_prefetch: + /* Prefetch area to be written into the cache if we're caching + * this file. We need to do this before we get a lock on the + * page in case there's more than one writer competing for the + * same cache block. + */ + if (!PageUptodate(page)) { + ret = netfs_prefetch_for_write(file, page, region->dirty.end, + bytes, always_fill); + kdebug("prefetch %zx", ret); + if (ret < 0) + goto error_page; + } + + if (mapping_writably_mapped(page->mapping)) + flush_dcache_page(page); + copied = copy_page_from_iter_atomic(page, offset, bytes, i); + flush_dcache_page(page); + kdebug("copied %zx", copied); + + /* Deal with a (partially) failed copy */ + if (!PageUptodate(page)) { + if (copied == 0) { + ret = -EFAULT; + goto error_page; + } + if (copied < bytes) { + iov_iter_revert(i, copied); + always_fill = true; + goto redo_prefetch; + } + SetPageUptodate(page); + } + + /* Update the inode size if we moved the EOF marker */ + new_pos = region->dirty.end + copied; + i_size = i_size_read(file_inode(file)); + if (new_pos > i_size) { + if (ctx->ops->update_i_size) { + ctx->ops->update_i_size(file, new_pos); + } else { + i_size_write(file_inode(file), new_pos); + fscache_update_cookie(ctx->cache, NULL, &new_pos); + } + } + + /* Update the region appropriately */ + if (i_size > region->i_size) + region->i_size = i_size; + smp_store_release(®ion->dirty.end, new_pos); + + trace_netfs_dirty(ctx, region, NULL, netfs_dirty_trace_modified); + set_page_dirty(page); + unlock_page(page); + put_page(page); + page = NULL; + + cond_resched(); + + written += copied; + + balance_dirty_pages_ratelimited(file->f_mapping); + } while (iov_iter_count(i)); + +out: + if (likely(written)) { + kdebug("written"); + iocb->ki_pos += written; + + /* Flush and wait for a write that requires immediate synchronisation. */ + if (region->type == NETFS_REGION_DSYNC) { + kdebug("dsync"); + spin_lock(&ctx->lock); + netfs_flush_region(ctx, region, netfs_dirty_trace_flush_dsync); + spin_unlock(&ctx->lock); + + ret = wait_on_region(region, NETFS_REGION_IS_COMPLETE); + if (ret < 0) + written = ret; + } + } + + netfs_commit_write(ctx, region); + return written ? written : ret; + +error_page: + unlock_page(page); + put_page(page); + goto out; +} + +/** + * netfs_file_write_iter - write data to a file + * @iocb: IO state structure + * @from: iov_iter with data to write + * + * This is a wrapper around __generic_file_write_iter() to be used by most + * filesystems. It takes care of syncing the file in case of O_SYNC file + * and acquires i_mutex as needed. + * Return: + * * negative error code if no data has been written at all of + * vfs_fsync_range() failed for a synchronous write + * * number of bytes written, even for truncated writes + */ +ssize_t netfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from) +{ + struct netfs_dirty_region *region = NULL; + struct file *file = iocb->ki_filp; + struct inode *inode = file->f_mapping->host; + struct netfs_i_context *ctx = netfs_i_context(inode); + enum netfs_region_type type; + unsigned long flags = 0; + ssize_t ret; + + printk("\n"); + kenter("%llx,%zx,%llx", iocb->ki_pos, iov_iter_count(from), i_size_read(inode)); + + inode_lock(inode); + ret = generic_write_checks(iocb, from); + if (ret <= 0) + goto error_unlock; + + if (iocb->ki_flags & IOCB_DIRECT) + type = NETFS_REGION_DIO; + if (iocb->ki_flags & IOCB_DSYNC) + type = NETFS_REGION_DSYNC; + else + type = NETFS_REGION_ORDINARY; + if (iocb->ki_flags & IOCB_SYNC) + __set_bit(NETFS_REGION_SYNC, &flags); + + region = netfs_prepare_region(inode, file, iocb->ki_pos, + iov_iter_count(from), type, flags); + if (IS_ERR(region)) { + ret = PTR_ERR(region); + goto error_unlock; + } + + trace_netfs_write_iter(region, iocb, from); + + /* We can write back this queue in page reclaim */ + current->backing_dev_info = inode_to_bdi(inode); + ret = file_remove_privs(file); + if (ret) + goto error_unlock; + + ret = file_update_time(file); + if (ret) + goto error_unlock; + + inode_unlock(inode); + + ret = wait_on_region(region, NETFS_REGION_IS_RESERVED); + if (ret < 0) + goto error; + + ret = netfs_activate_write(ctx, region); + if (ret < 0) + goto error; + + /* The region excludes overlapping writes and is used to synchronise + * versus flushes. + */ + if (iocb->ki_flags & IOCB_DIRECT) + ret = -EOPNOTSUPP; //netfs_file_direct_write(region, iocb, from); + else + ret = netfs_perform_write(region, iocb, from); + +out: + netfs_put_dirty_region(ctx, region, netfs_region_trace_put_write_iter); + current->backing_dev_info = NULL; + return ret; + +error_unlock: + inode_unlock(inode); +error: + if (region) + netfs_commit_write(ctx, region); + goto out; +} +EXPORT_SYMBOL(netfs_file_write_iter); diff --git a/include/linux/netfs.h b/include/linux/netfs.h index 35bcd916c3a0..fc91711d3178 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -165,17 +165,95 @@ struct netfs_read_request { */ struct netfs_i_context { const struct netfs_request_ops *ops; + struct list_head pending_writes; /* List of writes waiting to be begin */ + struct list_head active_writes; /* List of writes being applied */ + struct list_head dirty_regions; /* List of dirty regions in the pagecache */ + struct list_head flush_groups; /* Writeable region ordering queue */ + struct list_head flush_queue; /* Regions that need to be flushed */ #ifdef CONFIG_FSCACHE struct fscache_cookie *cache; #endif unsigned long flags; #define NETFS_ICTX_NEW_CONTENT 0 /* Set if file has new content (create/trunc-0) */ + spinlock_t lock; + unsigned int rsize; /* Maximum read size */ + unsigned int wsize; /* Maximum write size */ + unsigned int bsize; /* Min block size for bounding box */ + unsigned int inval_counter; /* Number of invalidations made */ +}; + +/* + * Descriptor for a set of writes that will need to be flushed together. + */ +struct netfs_flush_group { + struct list_head group_link; /* Link in i_context->flush_groups */ + struct list_head region_list; /* List of regions in this group */ + void *netfs_priv; + refcount_t ref; + bool flush; +}; + +struct netfs_range { + unsigned long long start; /* Start of region */ + unsigned long long end; /* End of region */ +}; + +/* State of a netfs_dirty_region */ +enum netfs_region_state { + NETFS_REGION_IS_PENDING, /* Proposed write is waiting on an active write */ + NETFS_REGION_IS_RESERVED, /* Writable region is reserved, waiting on flushes */ + NETFS_REGION_IS_ACTIVE, /* Write is actively modifying the pagecache */ + NETFS_REGION_IS_DIRTY, /* Region is dirty */ + NETFS_REGION_IS_FLUSHING, /* Region is being flushed */ + NETFS_REGION_IS_COMPLETE, /* Region has been completed (stored/invalidated) */ +} __attribute__((mode(byte))); + +enum netfs_region_type { + NETFS_REGION_ORDINARY, /* Ordinary write */ + NETFS_REGION_DIO, /* Direct I/O write */ + NETFS_REGION_DSYNC, /* O_DSYNC/RWF_DSYNC write */ +} __attribute__((mode(byte))); + +/* + * Descriptor for a dirty region that has a common set of parameters and can + * feasibly be written back in one go. These are held in an ordered list. + * + * Regions are not allowed to overlap, though they may be merged. + */ +struct netfs_dirty_region { + struct netfs_flush_group *group; + struct list_head active_link; /* Link in i_context->pending/active_writes */ + struct list_head dirty_link; /* Link in i_context->dirty_regions */ + struct list_head flush_link; /* Link in group->region_list or + * i_context->flush_queue */ + spinlock_t lock; + void *netfs_priv; /* Private data for the netfs */ + struct netfs_range bounds; /* Bounding box including all affected pages */ + struct netfs_range reserved; /* The region reserved against other writes */ + struct netfs_range dirty; /* The region that has been modified */ + loff_t i_size; /* Size of the file */ + enum netfs_region_type type; + enum netfs_region_state state; + unsigned long flags; +#define NETFS_REGION_SYNC 0 /* Set if metadata sync required (RWF_SYNC) */ +#define NETFS_REGION_FLUSH_Q 1 /* Set if region is on flush queue */ +#define NETFS_REGION_SUPERSEDED 2 /* Set if region is being superseded */ + unsigned int debug_id; + refcount_t ref; +}; + +enum netfs_write_compatibility { + NETFS_WRITES_COMPATIBLE, /* Dirty regions can be directly merged */ + NETFS_WRITES_SUPERSEDE, /* Second write can supersede the first without first + * having to be flushed (eg. authentication, DSYNC) */ + NETFS_WRITES_INCOMPATIBLE, /* Second write must wait for first (eg. DIO, ceph snap) */ }; /* * Operations the network filesystem can/must provide to the helpers. */ struct netfs_request_ops { + /* Read request handling */ void (*init_rreq)(struct netfs_read_request *rreq, struct file *file); int (*begin_cache_operation)(struct netfs_read_request *rreq); void (*expand_readahead)(struct netfs_read_request *rreq); @@ -186,6 +264,17 @@ struct netfs_request_ops { struct page *page, void **_fsdata); void (*done)(struct netfs_read_request *rreq); void (*cleanup)(struct address_space *mapping, void *netfs_priv); + + /* Dirty region handling */ + void (*init_dirty_region)(struct netfs_dirty_region *region, struct file *file); + void (*split_dirty_region)(struct netfs_dirty_region *region); + void (*free_dirty_region)(struct netfs_dirty_region *region); + enum netfs_write_compatibility (*is_write_compatible)( + struct netfs_i_context *ctx, + struct netfs_dirty_region *old_region, + struct netfs_dirty_region *candidate); + bool (*check_compatible_write)(struct netfs_dirty_region *region, struct file *file); + void (*update_i_size)(struct file *file, loff_t i_size); }; /* @@ -234,9 +323,11 @@ extern int netfs_readpage(struct file *, struct page *); extern int netfs_write_begin(struct file *, struct address_space *, loff_t, unsigned int, unsigned int, struct page **, void **); +extern ssize_t netfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from); extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool); extern void netfs_stats_show(struct seq_file *); +extern struct netfs_flush_group *netfs_new_flush_group(struct inode *, void *); /** * netfs_i_context - Get the netfs inode context from the inode @@ -256,6 +347,13 @@ static inline void netfs_i_context_init(struct inode *inode, struct netfs_i_context *ctx = netfs_i_context(inode); ctx->ops = ops; + ctx->bsize = PAGE_SIZE; + INIT_LIST_HEAD(&ctx->pending_writes); + INIT_LIST_HEAD(&ctx->active_writes); + INIT_LIST_HEAD(&ctx->dirty_regions); + INIT_LIST_HEAD(&ctx->flush_groups); + INIT_LIST_HEAD(&ctx->flush_queue); + spin_lock_init(&ctx->lock); } /** diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h index 04ac29fc700f..808433e6ddd3 100644 --- a/include/trace/events/netfs.h +++ b/include/trace/events/netfs.h @@ -23,6 +23,7 @@ enum netfs_read_trace { netfs_read_trace_readahead, netfs_read_trace_readpage, netfs_read_trace_write_begin, + netfs_read_trace_prefetch_for_write, }; enum netfs_rreq_trace { @@ -56,12 +57,43 @@ enum netfs_failure { netfs_fail_prepare_write, }; +enum netfs_dirty_trace { + netfs_dirty_trace_active, + netfs_dirty_trace_commit, + netfs_dirty_trace_complete, + netfs_dirty_trace_flush_conflict, + netfs_dirty_trace_flush_dsync, + netfs_dirty_trace_merged_back, + netfs_dirty_trace_merged_forw, + netfs_dirty_trace_merged_sub, + netfs_dirty_trace_modified, + netfs_dirty_trace_new, + netfs_dirty_trace_reserved, + netfs_dirty_trace_split, + netfs_dirty_trace_start_pending, + netfs_dirty_trace_superseded, + netfs_dirty_trace_supersedes, + netfs_dirty_trace_wait_active, + netfs_dirty_trace_wait_pend, +}; + +enum netfs_region_trace { + netfs_region_trace_get_dirty, + netfs_region_trace_get_wreq, + netfs_region_trace_put_discard, + netfs_region_trace_put_merged, + netfs_region_trace_put_write_iter, + netfs_region_trace_free, + netfs_region_trace_new, +}; + #endif #define netfs_read_traces \ EM(netfs_read_trace_expanded, "EXPANDED ") \ EM(netfs_read_trace_readahead, "READAHEAD") \ EM(netfs_read_trace_readpage, "READPAGE ") \ + EM(netfs_read_trace_prefetch_for_write, "PREFETCHW") \ E_(netfs_read_trace_write_begin, "WRITEBEGN") #define netfs_rreq_traces \ @@ -98,6 +130,46 @@ enum netfs_failure { EM(netfs_fail_short_write_begin, "short-write-begin") \ E_(netfs_fail_prepare_write, "prep-write") +#define netfs_region_types \ + EM(NETFS_REGION_ORDINARY, "ORD") \ + EM(NETFS_REGION_DIO, "DIO") \ + E_(NETFS_REGION_DSYNC, "DSY") + +#define netfs_region_states \ + EM(NETFS_REGION_IS_PENDING, "pend") \ + EM(NETFS_REGION_IS_RESERVED, "resv") \ + EM(NETFS_REGION_IS_ACTIVE, "actv") \ + EM(NETFS_REGION_IS_DIRTY, "drty") \ + EM(NETFS_REGION_IS_FLUSHING, "flsh") \ + E_(NETFS_REGION_IS_COMPLETE, "done") + +#define netfs_dirty_traces \ + EM(netfs_dirty_trace_active, "ACTIVE ") \ + EM(netfs_dirty_trace_commit, "COMMIT ") \ + EM(netfs_dirty_trace_complete, "COMPLETE ") \ + EM(netfs_dirty_trace_flush_conflict, "FLSH CONFL") \ + EM(netfs_dirty_trace_flush_dsync, "FLSH DSYNC") \ + EM(netfs_dirty_trace_merged_back, "MERGE BACK") \ + EM(netfs_dirty_trace_merged_forw, "MERGE FORW") \ + EM(netfs_dirty_trace_merged_sub, "SUBSUMED ") \ + EM(netfs_dirty_trace_modified, "MODIFIED ") \ + EM(netfs_dirty_trace_new, "NEW ") \ + EM(netfs_dirty_trace_reserved, "RESERVED ") \ + EM(netfs_dirty_trace_split, "SPLIT ") \ + EM(netfs_dirty_trace_start_pending, "START PEND") \ + EM(netfs_dirty_trace_superseded, "SUPERSEDED") \ + EM(netfs_dirty_trace_supersedes, "SUPERSEDES") \ + EM(netfs_dirty_trace_wait_active, "WAIT ACTV ") \ + E_(netfs_dirty_trace_wait_pend, "WAIT PEND ") + +#define netfs_region_traces \ + EM(netfs_region_trace_get_dirty, "GET DIRTY ") \ + EM(netfs_region_trace_get_wreq, "GET WREQ ") \ + EM(netfs_region_trace_put_discard, "PUT DISCARD") \ + EM(netfs_region_trace_put_merged, "PUT MERGED ") \ + EM(netfs_region_trace_put_write_iter, "PUT WRITER ") \ + EM(netfs_region_trace_free, "FREE ") \ + E_(netfs_region_trace_new, "NEW ") /* * Export enum symbols via userspace. @@ -112,6 +184,9 @@ netfs_rreq_traces; netfs_sreq_sources; netfs_sreq_traces; netfs_failures; +netfs_region_types; +netfs_region_states; +netfs_dirty_traces; /* * Now redefine the EM() and E_() macros to map the enums to the strings that @@ -255,6 +330,111 @@ TRACE_EVENT(netfs_failure, __entry->error) ); +TRACE_EVENT(netfs_write_iter, + TP_PROTO(struct netfs_dirty_region *region, struct kiocb *iocb, + struct iov_iter *from), + + TP_ARGS(region, iocb, from), + + TP_STRUCT__entry( + __field(unsigned int, region ) + __field(unsigned long long, start ) + __field(size_t, len ) + __field(unsigned int, flags ) + ), + + TP_fast_assign( + __entry->region = region->debug_id; + __entry->start = iocb->ki_pos; + __entry->len = iov_iter_count(from); + __entry->flags = iocb->ki_flags; + ), + + TP_printk("D=%x WRITE-ITER s=%llx l=%zx f=%x", + __entry->region, __entry->start, __entry->len, __entry->flags) + ); + +TRACE_EVENT(netfs_ref_region, + TP_PROTO(unsigned int region_debug_id, int ref, + enum netfs_region_trace what), + + TP_ARGS(region_debug_id, ref, what), + + TP_STRUCT__entry( + __field(unsigned int, region ) + __field(int, ref ) + __field(enum netfs_region_trace, what ) + ), + + TP_fast_assign( + __entry->region = region_debug_id; + __entry->ref = ref; + __entry->what = what; + ), + + TP_printk("D=%x %s r=%u", + __entry->region, + __print_symbolic(__entry->what, netfs_region_traces), + __entry->ref) + ); + +TRACE_EVENT(netfs_dirty, + TP_PROTO(struct netfs_i_context *ctx, + struct netfs_dirty_region *region, + struct netfs_dirty_region *region2, + enum netfs_dirty_trace why), + + TP_ARGS(ctx, region, region2, why), + + TP_STRUCT__entry( + __field(ino_t, ino ) + __field(unsigned long long, bounds_start ) + __field(unsigned long long, bounds_end ) + __field(unsigned long long, reserved_start ) + __field(unsigned long long, reserved_end ) + __field(unsigned long long, dirty_start ) + __field(unsigned long long, dirty_end ) + __field(unsigned int, debug_id ) + __field(unsigned int, debug_id2 ) + __field(enum netfs_region_type, type ) + __field(enum netfs_region_state, state ) + __field(unsigned short, flags ) + __field(unsigned int, ref ) + __field(enum netfs_dirty_trace, why ) + ), + + TP_fast_assign( + __entry->ino = (((struct inode *)ctx) - 1)->i_ino; + __entry->why = why; + __entry->bounds_start = region->bounds.start; + __entry->bounds_end = region->bounds.end; + __entry->reserved_start = region->reserved.start; + __entry->reserved_end = region->reserved.end; + __entry->dirty_start = region->dirty.start; + __entry->dirty_end = region->dirty.end; + __entry->debug_id = region->debug_id; + __entry->type = region->type; + __entry->state = region->state; + __entry->flags = region->flags; + __entry->debug_id2 = region2 ? region2->debug_id : 0; + ), + + TP_printk("i=%lx D=%x %s %s dt=%04llx-%04llx bb=%04llx-%04llx rs=%04llx-%04llx %s f=%x XD=%x", + __entry->ino, __entry->debug_id, + __print_symbolic(__entry->why, netfs_dirty_traces), + __print_symbolic(__entry->type, netfs_region_types), + __entry->dirty_start, + __entry->dirty_end, + __entry->bounds_start, + __entry->bounds_end, + __entry->reserved_start, + __entry->reserved_end, + __print_symbolic(__entry->state, netfs_region_states), + __entry->flags, + __entry->debug_id2 + ) + ); + #endif /* _TRACE_NETFS_H */ /* This part must be outside protection */