@@ -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)
@@ -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 *);
@@ -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
@@ -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
new file mode 100644
@@ -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 <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/uio.h>
+#include <linux/sched/mm.h>
+#include <linux/backing-dev.h>
+#include <linux/task_io_accounting_ops.h>
+#include <linux/netfs.h>
+#include "internal.h"
+#include <trace/events/netfs.h>
+
+/*
+ * 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;
+}
@@ -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)
new file mode 100644
@@ -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 <linux/export.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/backing-dev.h>
+#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);
+ }
+}
@@ -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;
+}
@@ -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);
new file mode 100644
@@ -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 <linux/export.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/backing-dev.h>
+#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);
@@ -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);
}
/**
@@ -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 */
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