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authorLukas Czerner <lczerner@redhat.com>2017-09-21 08:16:29 -0600
committerJens Axboe <axboe@kernel.dk>2017-09-25 08:56:05 -0600
commit332391a9935da939319e473b4680e173df75afcf (patch)
tree52609917ecaadeea19dab63feaa4229af5a88561 /mm
parentbb1cc74790eb51f52d23c6e5fd9a3bb16030c3d8 (diff)
download96b-common-332391a9935da939319e473b4680e173df75afcf.tar.gz
fs: Fix page cache inconsistency when mixing buffered and AIO DIO
Currently when mixing buffered reads and asynchronous direct writes it is possible to end up with the situation where we have stale data in the page cache while the new data is already written to disk. This is permanent until the affected pages are flushed away. Despite the fact that mixing buffered and direct IO is ill-advised it does pose a thread for a data integrity, is unexpected and should be fixed. Fix this by deferring completion of asynchronous direct writes to a process context in the case that there are mapped pages to be found in the inode. Later before the completion in dio_complete() invalidate the pages in question. This ensures that after the completion the pages in the written area are either unmapped, or populated with up-to-date data. Also do the same for the iomap case which uses iomap_dio_complete() instead. This has a side effect of deferring the completion to a process context for every AIO DIO that happens on inode that has pages mapped. However since the consensus is that this is ill-advised practice the performance implication should not be a problem. This was based on proposal from Jeff Moyer, thanks! Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Lukas Czerner <lczerner@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'mm')
-rw-r--r--mm/filemap.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 870971e20967..db250d0e0565 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2926,9 +2926,15 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
* 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...
+ *
+ * Most of the time we do not need this since dio_complete() will do
+ * the invalidation for us. However there are some file systems that
+ * do not end up with dio_complete() being called, so let's not break
+ * them by removing it completely
*/
- invalidate_inode_pages2_range(mapping,
- pos >> PAGE_SHIFT, end);
+ if (mapping->nrpages)
+ invalidate_inode_pages2_range(mapping,
+ pos >> PAGE_SHIFT, end);
if (written > 0) {
pos += written;