summaryrefslogtreecommitdiffstats
path: root/fs/ext4
diff options
context:
space:
mode:
authorPranay Kr. Srivastava <pranjas@gmail.com>2016-07-04 10:24:52 -0400
committerTheodore Ts'o <tytso@mit.edu>2016-07-04 10:24:52 -0400
commit4743f83990614af6adb09ea7aa3c37b78c4031ab (patch)
tree86784086a26c2d2181270426145540310de8acd0 /fs/ext4
parent646caa9c8e196880b41cd3e3d33a2ebc752bdb85 (diff)
downloadlinux-4743f83990614af6adb09ea7aa3c37b78c4031ab.tar.bz2
ext4: Fix WARN_ON_ONCE in ext4_commit_super()
If there are racing calls to ext4_commit_super() it's possible for another writeback of the superblock to result in the buffer being marked with an error after we check if the buffer is marked as having a write error and the buffer up-to-date flag is set again. If that happens mark_buffer_dirty() can end up throwing a WARN_ON_ONCE. Fix this by moving this check to write before we call write_buffer_dirty(), and keeping the buffer locked during this whole sequence. Signed-off-by: Pranay Kr. Srivastava <pranjas@gmail.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4')
-rw-r--r--fs/ext4/super.c30
1 files changed, 16 insertions, 14 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 6e2f9d628c48..5664ee66b301 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4327,20 +4327,6 @@ static int ext4_commit_super(struct super_block *sb, int sync)
if (!sbh || block_device_ejected(sb))
return error;
- if (buffer_write_io_error(sbh)) {
- /*
- * Oh, dear. A previous attempt to write the
- * superblock failed. This could happen because the
- * USB device was yanked out. Or it could happen to
- * be a transient write error and maybe the block will
- * be remapped. Nothing we can do but to retry the
- * write and hope for the best.
- */
- ext4_msg(sb, KERN_ERR, "previous I/O error to "
- "superblock detected");
- clear_buffer_write_io_error(sbh);
- set_buffer_uptodate(sbh);
- }
/*
* If the file system is mounted read-only, don't update the
* superblock write time. This avoids updating the superblock
@@ -4371,7 +4357,23 @@ static int ext4_commit_super(struct super_block *sb, int sync)
&EXT4_SB(sb)->s_freeinodes_counter));
BUFFER_TRACE(sbh, "marking dirty");
ext4_superblock_csum_set(sb);
+ lock_buffer(sbh);
+ if (buffer_write_io_error(sbh)) {
+ /*
+ * Oh, dear. A previous attempt to write the
+ * superblock failed. This could happen because the
+ * USB device was yanked out. Or it could happen to
+ * be a transient write error and maybe the block will
+ * be remapped. Nothing we can do but to retry the
+ * write and hope for the best.
+ */
+ ext4_msg(sb, KERN_ERR, "previous I/O error to "
+ "superblock detected");
+ clear_buffer_write_io_error(sbh);
+ set_buffer_uptodate(sbh);
+ }
mark_buffer_dirty(sbh);
+ unlock_buffer(sbh);
if (sync) {
error = __sync_dirty_buffer(sbh,
test_opt(sb, BARRIER) ? WRITE_FUA : WRITE_SYNC);