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authorEryu Guan <eguan@redhat.com>2017-10-13 09:47:46 -0700
committerDarrick J. Wong <darrick.wong@oracle.com>2017-10-16 12:11:56 -0700
commit5e25c269e17de4c5a23ce886cda612b01365a944 (patch)
treeb89ee04551f1160174b58954002a268c3647b927 /fs/direct-io.c
parent793d7dbe6d82a50b9d14bf992b9eaacb70a11ce6 (diff)
downloadlwn-5e25c269e17de4c5a23ce886cda612b01365a944.tar.gz
lwn-5e25c269e17de4c5a23ce886cda612b01365a944.zip
fs: invalidate page cache after end_io() in dio completion
Commit 332391a9935d ("fs: Fix page cache inconsistency when mixing buffered and AIO DIO") moved page cache invalidation from iomap_dio_rw() to iomap_dio_complete() for iomap based direct write path, but before the dio->end_io() call, and it re-introdued the bug fixed by commit c771c14baa33 ("iomap: invalidate page caches should be after iomap_dio_complete() in direct write"). I found this because fstests generic/418 started failing on XFS with v4.14-rc3 kernel, which is the regression test for this specific bug. So similarly, fix it by moving dio->end_io() (which does the unwritten extent conversion) before page cache invalidation, to make sure next buffer read reads the final real allocations not unwritten extents. I also add some comments about why should end_io() go first in case we get it wrong again in the future. Note that, there's no such problem in the non-iomap based direct write path, because we didn't remove the page cache invalidation after the ->direct_IO() in generic_file_direct_write() call, but I decided to fix dio_complete() too so we don't leave a landmine there, also be consistent with iomap_dio_complete(). Fixes: 332391a9935d ("fs: Fix page cache inconsistency when mixing buffered and AIO DIO") Signed-off-by: Eryu Guan <eguan@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Diffstat (limited to 'fs/direct-io.c')
-rw-r--r--fs/direct-io.c20
1 files changed, 12 insertions, 8 deletions
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 96415c65bbdc..19ac3fe57deb 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -259,12 +259,24 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
if (ret == 0)
ret = transferred;
+ if (dio->end_io) {
+ // XXX: ki_pos??
+ err = dio->end_io(dio->iocb, offset, ret, dio->private);
+ if (err)
+ ret = err;
+ }
+
/*
* 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...
+ *
+ * And this page cache invalidation has to be after dio->end_io(), as
+ * some filesystems convert unwritten extents to real allocations in
+ * end_io() when necessary, otherwise a racing buffer read would cache
+ * zeros from unwritten extents.
*/
if (ret > 0 && dio->op == REQ_OP_WRITE &&
dio->inode->i_mapping->nrpages) {
@@ -274,14 +286,6 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
WARN_ON_ONCE(err);
}
- if (dio->end_io) {
-
- // XXX: ki_pos??
- err = dio->end_io(dio->iocb, offset, ret, dio->private);
- if (err)
- ret = err;
- }
-
if (!(dio->flags & DIO_SKIP_DIO_COUNT))
inode_dio_end(dio->inode);