The patch titled
Subject: fs: return if direct write will trigger writeback
has been added to the -mm tree. Its filename is
fs-return-if-direct-write-will-trigger-writeback.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fs-return-if-direct-write-will-trigger-writeback.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fs-return-if-direct-write-will-trigger-writeback.patch
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------------------------------------------------------
From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
Subject: fs: return if direct write will trigger writeback
Find out if the write will trigger a wait due to writeback. If yes,
return -EAGAIN.
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.
Link: http://lkml.kernel.org/r/20170615160002.17233-6-rgoldwyn@xxxxxxx
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx>
Cc: Chris Mason <clm@xxxxxx>
Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Cc: David Sterba <dsterba@xxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Josef Bacik <jbacik@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff -puN mm/filemap.c~fs-return-if-direct-write-will-trigger-writeback mm/filemap.c
--- a/mm/filemap.c~fs-return-if-direct-write-will-trigger-writeback
+++ a/mm/filemap.c
@@ -2675,6 +2675,9 @@ inline ssize_t generic_write_checks(stru
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);
@@ -2743,9 +2746,17 @@ generic_file_direct_write(struct kiocb *
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
_
Patches currently in -mm which might be from rgoldwyn@xxxxxxxx are
fs-separate-out-kiocb-flags-setup-based-on-rwf_-flags.patch
fs-introduce-filemap_range_has_page.patch
fs-use-rwf_-flags-for-aio-operations.patch
fs-introduce-rwf_nowait-and-fmode_aio_nowait.patch
fs-return-if-direct-write-will-trigger-writeback.patch
fs-introduce-iomap_nowait.patch
block-return-on-congested-block-device.patch
ext4-nowait-aio-support.patch
xfs-nowait-aio-support.patch
btrfs-nowait-aio-support.patch
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