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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [RFC PATCH 1/2] cifs: Transition from ->readpages() to ->readahead() From: David Howells To: smfrench@gmail.com, nspmangalore@gmail.com Cc: Matthew Wilcox , Jeff Layton , linux-cifs@vger.kernel.org, linux-cachefs@redhat.com, dhowells@redhat.com Date: Mon, 24 Jan 2022 16:58:05 +0000 Message-ID: <164304348524.2349137.12280578401440758411.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org Transition the cifs filesystem from using the old ->readpages() method to using the new ->readahead() method. For the moment, this removes any invocation of fscache to read data from the local cache, leaving that to another patch. Signed-off-by: David Howells cc: Steve French cc: Shyam Prasad N cc: Matthew Wilcox cc: Jeff Layton cc: linux-cifs@vger.kernel.org cc: linux-cachefs@redhat.com --- fs/cifs/file.c | 169 +++++++++++--------------------------------------------- 1 file changed, 33 insertions(+), 136 deletions(-) diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 59334be9ed3b..384a7323702f 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -4269,8 +4269,6 @@ cifs_readv_complete(struct work_struct *work) for (i = 0; i < rdata->nr_pages; i++) { struct page *page = rdata->pages[i]; - lru_cache_add(page); - if (rdata->result == 0 || (rdata->result == -EAGAIN && got_bytes)) { flush_dcache_page(page); @@ -4340,7 +4338,6 @@ readpages_fill_pages(struct TCP_Server_Info *server, * fill them until the writes are flushed. */ zero_user(page, 0, PAGE_SIZE); - lru_cache_add(page); flush_dcache_page(page); SetPageUptodate(page); unlock_page(page); @@ -4350,7 +4347,6 @@ readpages_fill_pages(struct TCP_Server_Info *server, continue; } else { /* no need to hold page hostage */ - lru_cache_add(page); unlock_page(page); put_page(page); rdata->pages[i] = NULL; @@ -4393,92 +4389,16 @@ cifs_readpages_copy_into_pages(struct TCP_Server_Info *server, return readpages_fill_pages(server, rdata, iter, iter->count); } -static int -readpages_get_pages(struct address_space *mapping, struct list_head *page_list, - unsigned int rsize, struct list_head *tmplist, - unsigned int *nr_pages, loff_t *offset, unsigned int *bytes) -{ - struct page *page, *tpage; - unsigned int expected_index; - int rc; - gfp_t gfp = readahead_gfp_mask(mapping); - - INIT_LIST_HEAD(tmplist); - - page = lru_to_page(page_list); - - /* - * Lock the page and put it in the cache. Since no one else - * should have access to this page, we're safe to simply set - * PG_locked without checking it first. - */ - __SetPageLocked(page); - rc = add_to_page_cache_locked(page, mapping, - page->index, gfp); - - /* give up if we can't stick it in the cache */ - if (rc) { - __ClearPageLocked(page); - return rc; - } - - /* move first page to the tmplist */ - *offset = (loff_t)page->index << PAGE_SHIFT; - *bytes = PAGE_SIZE; - *nr_pages = 1; - list_move_tail(&page->lru, tmplist); - - /* now try and add more pages onto the request */ - expected_index = page->index + 1; - list_for_each_entry_safe_reverse(page, tpage, page_list, lru) { - /* discontinuity ? */ - if (page->index != expected_index) - break; - - /* would this page push the read over the rsize? */ - if (*bytes + PAGE_SIZE > rsize) - break; - - __SetPageLocked(page); - rc = add_to_page_cache_locked(page, mapping, page->index, gfp); - if (rc) { - __ClearPageLocked(page); - break; - } - list_move_tail(&page->lru, tmplist); - (*bytes) += PAGE_SIZE; - expected_index++; - (*nr_pages)++; - } - return rc; -} - -static int cifs_readpages(struct file *file, struct address_space *mapping, - struct list_head *page_list, unsigned num_pages) +static void cifs_readahead(struct readahead_control *ractl) { int rc; - int err = 0; - struct list_head tmplist; - struct cifsFileInfo *open_file = file->private_data; - struct cifs_sb_info *cifs_sb = CIFS_FILE_SB(file); + struct cifsFileInfo *open_file = ractl->file->private_data; + struct cifs_sb_info *cifs_sb = CIFS_FILE_SB(ractl->file); struct TCP_Server_Info *server; pid_t pid; unsigned int xid; xid = get_xid(); - /* - * Reads as many pages as possible from fscache. Returns -ENOBUFS - * immediately if the cookie is negative - * - * After this point, every page in the list might have PG_fscache set, - * so we will need to clean that up off of every page we don't use. - */ - rc = cifs_readpages_from_fscache(mapping->host, mapping, page_list, - &num_pages); - if (rc == 0) { - free_xid(xid); - return rc; - } if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RWPIDFORWARD) pid = open_file->pid; @@ -4489,39 +4409,32 @@ static int cifs_readpages(struct file *file, struct address_space *mapping, server = cifs_pick_channel(tlink_tcon(open_file->tlink)->ses); cifs_dbg(FYI, "%s: file=%p mapping=%p num_pages=%u\n", - __func__, file, mapping, num_pages); + __func__, ractl->file, ractl->mapping, readahead_count(ractl)); /* - * Start with the page at end of list and move it to private - * list. Do the same with any following pages until we hit - * the rsize limit, hit an index discontinuity, or run out of - * pages. Issue the async read and then start the loop again - * until the list is empty. - * - * Note that list order is important. The page_list is in - * the order of declining indexes. When we put the pages in - * the rdata->pages, then we want them in increasing order. + * Chop the readahead request up into rsize-sized read requests. */ - while (!list_empty(page_list) && !err) { - unsigned int i, nr_pages, bytes, rsize; - loff_t offset; - struct page *page, *tpage; + while (readahead_count(ractl) - ractl->_batch_count) { + unsigned int i, nr_pages, got, rsize; + struct page *page; struct cifs_readdata *rdata; struct cifs_credits credits_on_stack; struct cifs_credits *credits = &credits_on_stack; if (open_file->invalidHandle) { rc = cifs_reopen_file(open_file, true); - if (rc == -EAGAIN) - continue; - else if (rc) + if (rc) { + if (rc == -EAGAIN) + continue; break; + } } rc = server->ops->wait_mtu_credits(server, cifs_sb->ctx->rsize, &rsize, credits); if (rc) break; + nr_pages = min_t(size_t, rsize / PAGE_SIZE, readahead_count(ractl)); /* * Give up immediately if rsize is too small to read an entire @@ -4529,16 +4442,7 @@ static int cifs_readpages(struct file *file, struct address_space *mapping, * reach this point however since we set ra_pages to 0 when the * rsize is smaller than a cache page. */ - if (unlikely(rsize < PAGE_SIZE)) { - add_credits_and_wake_if(server, credits, 0); - free_xid(xid); - return 0; - } - - nr_pages = 0; - err = readpages_get_pages(mapping, page_list, rsize, &tmplist, - &nr_pages, &offset, &bytes); - if (!nr_pages) { + if (unlikely(!nr_pages)) { add_credits_and_wake_if(server, credits, 0); break; } @@ -4546,36 +4450,31 @@ static int cifs_readpages(struct file *file, struct address_space *mapping, rdata = cifs_readdata_alloc(nr_pages, cifs_readv_complete); if (!rdata) { /* best to give up if we're out of mem */ - list_for_each_entry_safe(page, tpage, &tmplist, lru) { - list_del(&page->lru); - lru_cache_add(page); - unlock_page(page); - put_page(page); - } - rc = -ENOMEM; add_credits_and_wake_if(server, credits, 0); break; } - rdata->cfile = cifsFileInfo_get(open_file); - rdata->server = server; - rdata->mapping = mapping; - rdata->offset = offset; - rdata->bytes = bytes; - rdata->pid = pid; - rdata->pagesz = PAGE_SIZE; - rdata->tailsz = PAGE_SIZE; + got = __readahead_batch(ractl, rdata->pages, nr_pages); + if (got != nr_pages) { + pr_warn("__readahead_batch() returned %u/%u\n", + got, nr_pages); + nr_pages = got; + } + + rdata->nr_pages = nr_pages; + rdata->bytes = readahead_batch_length(ractl); + rdata->cfile = cifsFileInfo_get(open_file); + rdata->server = server; + rdata->mapping = ractl->mapping; + rdata->offset = readahead_pos(ractl); + rdata->pid = pid; + rdata->pagesz = PAGE_SIZE; + rdata->tailsz = PAGE_SIZE; rdata->read_into_pages = cifs_readpages_read_into_pages; rdata->copy_into_pages = cifs_readpages_copy_into_pages; - rdata->credits = credits_on_stack; - - list_for_each_entry_safe(page, tpage, &tmplist, lru) { - list_del(&page->lru); - rdata->pages[rdata->nr_pages++] = page; - } + rdata->credits = credits_on_stack; rc = adjust_credits(server, &rdata->credits, rdata->bytes); - if (!rc) { if (rdata->cfile->invalidHandle) rc = -EAGAIN; @@ -4587,7 +4486,6 @@ static int cifs_readpages(struct file *file, struct address_space *mapping, add_credits_and_wake_if(server, &rdata->credits, 0); for (i = 0; i < rdata->nr_pages; i++) { page = rdata->pages[i]; - lru_cache_add(page); unlock_page(page); put_page(page); } @@ -4600,7 +4498,6 @@ static int cifs_readpages(struct file *file, struct address_space *mapping, } free_xid(xid); - return rc; } /* @@ -4924,7 +4821,7 @@ void cifs_oplock_break(struct work_struct *work) * In the non-cached mode (mount with cache=none), we shunt off direct read and write requests * so this method should never be called. * - * Direct IO is not yet supported in the cached mode. + * Direct IO is not yet supported in the cached mode. */ static ssize_t cifs_direct_io(struct kiocb *iocb, struct iov_iter *iter) @@ -5006,7 +4903,7 @@ static int cifs_set_page_dirty(struct page *page) const struct address_space_operations cifs_addr_ops = { .readpage = cifs_readpage, - .readpages = cifs_readpages, + .readahead = cifs_readahead, .writepage = cifs_writepage, .writepages = cifs_writepages, .write_begin = cifs_write_begin,