writeback: Fix data corruption on NFS

Commit 4f8ad655dbc8 "writeback: Refactor writeback_single_inode()" added
a condition to skip clean inode. However this is wrong in WB_SYNC_ALL
mode because there we also want to wait for outstanding writeback on
possibly clean inode. This was causing occasional data corruption issues
on NFS because it uses sync_inode() to make sure all outstanding writes
are flushed to the server before truncating the inode and with
sync_inode() returning prematurely file was sometimes extended back
by an outstanding write after it was truncated.

So modify the test to also check for pages under writeback in
WB_SYNC_ALL mode.

CC: stable@vger.kernel.org # >= 3.5
Fixes: 4f8ad655dbc82cf05d2edc11e66b78a42d38bf93
Reported-and-tested-by: Dan Duval <dan.duval@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 1f4a10ece2f1249d5ae9991bfdde4874019b3462..e0259a163f98e69000c28bdb78fcf2b77c2bed2d 100644 (file)
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -516,13 +516,16 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
        }
        WARN_ON(inode->i_state & I_SYNC);
        /*
-        * Skip inode if it is clean. We don't want to mess with writeback
-        * lists in this function since flusher thread may be doing for example
-        * sync in parallel and if we move the inode, it could get skipped. So
-        * here we make sure inode is on some writeback list and leave it there
-        * unless we have completely cleaned the inode.
+        * Skip inode if it is clean and we have no outstanding writeback in
+        * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
+        * function since flusher thread may be doing for example sync in
+        * parallel and if we move the inode, it could get skipped. So here we
+        * make sure inode is on some writeback list and leave it there unless
+        * we have completely cleaned the inode.
         */
-       if (!(inode->i_state & I_DIRTY))
+       if (!(inode->i_state & I_DIRTY) &&
+           (wbc->sync_mode != WB_SYNC_ALL ||
+            !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
                goto out;
        inode->i_state |= I_SYNC;
        spin_unlock(&inode->i_lock);