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@xxxxxxxxxx>
---
fs/direct-io.c | 20 ++++++++++++--------
fs/iomap.c | 41 ++++++++++++++++++++++++-----------------
2 files changed, 36 insertions(+), 25 deletions(-)
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 62cf812ed0e5..1dba6842c349 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);
diff --git a/fs/iomap.c b/fs/iomap.c
index be61cf742b5e..d4801f8dd4fd 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -714,23 +714,9 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
{
struct kiocb *iocb = dio->iocb;
struct inode *inode = file_inode(iocb->ki_filp);
+ loff_t offset = iocb->ki_pos;
ssize_t ret;
- /*
- * 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...
- */
- if (!dio->error &&
- (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
- ret = invalidate_inode_pages2_range(inode->i_mapping,
- iocb->ki_pos >> PAGE_SHIFT,
- (iocb->ki_pos + dio->size - 1) >> PAGE_SHIFT);
- WARN_ON_ONCE(ret);
- }
-
if (dio->end_io) {
ret = dio->end_io(iocb,
dio->error ? dio->error : dio->size,
@@ -742,12 +728,33 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
if (likely(!ret)) {
ret = dio->size;
/* check for short read */
- if (iocb->ki_pos + ret > dio->i_size &&
+ if (offset + ret > dio->i_size &&
!(dio->flags & IOMAP_DIO_WRITE))
- ret = dio->i_size - iocb->ki_pos;
+ ret = dio->i_size - offset;
iocb->ki_pos += ret;
}
+ /*
+ * 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 (!dio->error &&
+ (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
+ int err;
+ err = invalidate_inode_pages2_range(inode->i_mapping,
+ offset >> PAGE_SHIFT,
+ (offset + dio->size - 1) >> PAGE_SHIFT);
+ WARN_ON_ONCE(err);
+ }
+
inode_dio_end(file_inode(iocb->ki_filp));
kfree(dio);
--
2.13.6
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