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| author | Pranay Kr. Srivastava <pranjas@gmail.com> | 2016-07-04 10:24:52 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2016-07-04 10:24:52 -0400 |
| commit | 4743f83990614af6adb09ea7aa3c37b78c4031ab (patch) | |
| tree | 86784086a26c2d2181270426145540310de8acd0 /fs/ext4 | |
| parent | 646caa9c8e196880b41cd3e3d33a2ebc752bdb85 (diff) | |
| download | linux-4743f83990614af6adb09ea7aa3c37b78c4031ab.tar.gz | |
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.c | 30 |
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); |