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authorHarshad Shirwadkar <harshads@google.com>2018-01-10 00:13:13 -0500
committerTheodore Ts'o <tytso@mit.edu>2018-01-10 00:13:13 -0500
commitabbc3f9395c76d554a9ed27d4b1ebfb5d9b0e4ca (patch)
tree463181185ebf743f7dbee86b6215b20302b59b33 /fs/ext4
parent9ee93ba3c430d5b5140ab72738dc70c4c54990e0 (diff)
ext4: fix a race in the ext4 shutdown path
This patch fixes a race between the shutdown path and bio completion handling. In the ext4 direct io path with async io, after submitting a bio to the block layer, if journal starting fails, ext4_direct_IO_write() would bail out pretending that the IO failed. The caller would have had no way of knowing whether or not the IO was successfully submitted. So instead, we return -EIOCBQUEUED in this case. Now, the caller knows that the IO was submitted. The bio completion handler takes care of the error. Tested: Ran the shutdown xfstest test 461 in loop for over 2 hours across 4 machines resulting in over 400 runs. Verified that the race didn't occur. Usually the race was seen in about 20-30 iterations. Signed-off-by: Harshad Shirwadkar <harshads@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org
Diffstat (limited to 'fs/ext4')
-rw-r--r--fs/ext4/inode.c16
1 files changed, 12 insertions, 4 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 534a9130f625..4c2f8b57bdc7 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3767,10 +3767,18 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
/* Credits for sb + inode write */
handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
if (IS_ERR(handle)) {
- /* This is really bad luck. We've written the data
- * but cannot extend i_size. Bail out and pretend
- * the write failed... */
- ret = PTR_ERR(handle);
+ /*
+ * We wrote the data but cannot extend
+ * i_size. Bail out. In async io case, we do
+ * not return error here because we have
+ * already submmitted the corresponding
+ * bio. Returning error here makes the caller
+ * think that this IO is done and failed
+ * resulting in race with bio's completion
+ * handler.
+ */
+ if (!ret)
+ ret = PTR_ERR(handle);
if (inode->i_nlink)
ext4_orphan_del(NULL, inode);