From: Goldwyn Rodrigues <rgoldwyn@suse.de> To: linux-fsdevel@vger.kernel.org Cc: jack@suse.com, hch@infradead.org, linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, sagi@grimberg.me, avi@scylladb.com, axboe@kernel.dk, linux-api@vger.kernel.org, willy@infradead.org, Goldwyn Rodrigues <rgoldwyn@suse.com> Subject: [PATCH 3/8] nowait aio: return if direct write will trigger writeback Date: Wed, 15 Mar 2017 16:51:02 -0500 [thread overview] Message-ID: <20170315215107.5628-4-rgoldwyn@suse.de> (raw) In-Reply-To: <20170315215107.5628-1-rgoldwyn@suse.de> From: Goldwyn Rodrigues <rgoldwyn@suse.com> Find out if the write will trigger a wait due to writeback. If yes, return -EAGAIN. This introduces a new function filemap_range_has_page() which returns true if the file's mapping has a page within the range mentioned. Return -EINVAL for buffered AIO: there are multiple causes of delay such as page locks, dirty throttling logic, page loading from disk etc. which cannot be taken care of. Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> --- include/linux/fs.h | 2 ++ mm/filemap.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 49 insertions(+), 3 deletions(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index e8d9346..4a30e8f 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2514,6 +2514,8 @@ extern int filemap_fdatawait(struct address_space *); extern void filemap_fdatawait_keep_errors(struct address_space *); extern int filemap_fdatawait_range(struct address_space *, loff_t lstart, loff_t lend); +extern int filemap_range_has_page(struct address_space *, loff_t lstart, + loff_t lend); extern int filemap_write_and_wait(struct address_space *mapping); extern int filemap_write_and_wait_range(struct address_space *mapping, loff_t lstart, loff_t lend); diff --git a/mm/filemap.c b/mm/filemap.c index e08f3b9..c020e23 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -376,6 +376,39 @@ int filemap_flush(struct address_space *mapping) } EXPORT_SYMBOL(filemap_flush); +/** + * filemap_range_has_page - check if a page exists in range. + * @mapping: address space structure to wait for + * @start_byte: offset in bytes where the range starts + * @end_byte: offset in bytes where the range ends (inclusive) + * + * Find at least one page in the range supplied, usually used to check if + * direct writing in this range will trigger a writeback. + */ +int filemap_range_has_page(struct address_space *mapping, + loff_t start_byte, loff_t end_byte) +{ + pgoff_t index = start_byte >> PAGE_SHIFT; + pgoff_t end = end_byte >> PAGE_SHIFT; + struct pagevec pvec; + int ret; + + if (end_byte < start_byte) + return 0; + + if (mapping->nrpages == 0) + return 0; + + pagevec_init(&pvec, 0); + ret = pagevec_lookup(&pvec, mapping, index, 1); + if (!ret) + return 0; + ret = (pvec.pages[0]->index <= end); + pagevec_release(&pvec); + return ret; +} +EXPORT_SYMBOL(filemap_range_has_page); + static int __filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, loff_t end_byte) { @@ -2640,6 +2673,9 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) pos = iocb->ki_pos; + if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT)) + return -EINVAL; + if (limit != RLIM_INFINITY) { if (iocb->ki_pos >= limit) { send_sig(SIGXFSZ, current, 0); @@ -2709,9 +2745,17 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from) write_len = iov_iter_count(from); end = (pos + write_len - 1) >> PAGE_SHIFT; - written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); - if (written) - goto out; + if (iocb->ki_flags & IOCB_NOWAIT) { + /* If there are pages to writeback, return */ + if (filemap_range_has_page(inode->i_mapping, pos, + pos + iov_iter_count(from))) + return -EAGAIN; + } else { + written = filemap_write_and_wait_range(mapping, pos, + pos + write_len - 1); + if (written) + goto out; + } /* * After a write we want buffered reads to be sure to go to disk to get -- 2.10.2
next prev parent reply other threads:[~2017-03-15 21:51 UTC|newest] Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-03-15 21:50 [PATCH 0/8 v3] No wait AIO Goldwyn Rodrigues 2017-03-15 21:51 ` [PATCH 1/8] nowait aio: Introduce IOCB_RW_FLAG_NOWAIT Goldwyn Rodrigues 2017-03-15 21:51 ` [PATCH 2/8] nowait aio: Return if cannot get hold of i_rwsem Goldwyn Rodrigues 2017-03-15 21:51 ` Goldwyn Rodrigues [this message] 2017-03-16 13:08 ` [PATCH 3/8] nowait aio: return if direct write will trigger writeback Matthew Wilcox 2017-03-16 13:46 ` Goldwyn Rodrigues 2017-03-16 13:20 ` Matthew Wilcox [not found] ` <20170316132052.GG4033-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org> 2017-03-16 13:46 ` Goldwyn Rodrigues 2017-03-15 21:51 ` [PATCH 4/8] nowait-aio: Introduce IOMAP_NOWAIT Goldwyn Rodrigues 2017-03-15 21:51 ` [PATCH 5/8] nowait aio: return on congested block device Goldwyn Rodrigues [not found] ` <20170315215107.5628-6-rgoldwyn-l3A5Bk7waGM@public.gmane.org> 2017-03-16 14:33 ` Jens Axboe 2017-03-17 2:03 ` Ming Lei 2017-03-17 12:23 ` Goldwyn Rodrigues [not found] ` <eee4683d-9f44-434f-b97f-b0b24c7b3dab-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org> 2017-03-24 11:32 ` Goldwyn Rodrigues 2017-03-24 14:39 ` Jens Axboe 2017-03-16 21:31 ` Dave Chinner 2017-03-17 12:23 ` Goldwyn Rodrigues 2017-03-20 17:33 ` Jan Kara 2017-03-15 21:51 ` [PATCH 6/8] nowait aio: ext4 Goldwyn Rodrigues 2017-03-15 21:51 ` [PATCH 7/8] nowait aio: xfs Goldwyn Rodrigues 2017-03-15 21:51 ` [PATCH 8/8] nowait aio: btrfs Goldwyn Rodrigues 2017-04-03 18:52 [PATCH 0/8 v4] No wait AIO Goldwyn Rodrigues 2017-04-03 18:53 ` [PATCH 3/8] nowait aio: return if direct write will trigger writeback Goldwyn Rodrigues 2017-04-14 12:02 [PATCH 0/8 v6] No wait AIO Goldwyn Rodrigues 2017-04-14 12:02 ` [PATCH 3/8] nowait aio: return if direct write will trigger writeback Goldwyn Rodrigues 2017-05-09 12:22 [PATCH 0/8 v7] No wait AIO Goldwyn Rodrigues 2017-05-09 12:22 ` [PATCH 3/8] nowait aio: return if direct write will trigger writeback Goldwyn Rodrigues 2017-05-11 7:42 ` Christoph Hellwig
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