When I enabled ext4 debug for fault injection testing, I encountered the
following warning:

  EXT4-fs error (device sda): ext4_read_inode_bitmap:201: comm fsstress:
         Cannot read inode bitmap - block_group = 8, inode_bitmap = 1051
  WARNING: CPU: 0 PID: 511 at fs/buffer.c:1181 mark_buffer_dirty+0x1b3/0x1d0

The root cause of the issue lies in the improper implementation of ext4's
buffer_head read fault injection. The actual completion of buffer_head
read and the buffer_head fault injection are not atomic, which can lead
to the uptodate flag being cleared on normally used buffer_heads in race
conditions.

[CPU0]           [CPU1]         [CPU2]
ext4_read_inode_bitmap
  ext4_read_bh()
  <bh read complete>
                 ext4_read_inode_bitmap
                   if (buffer_uptodate(bh))
                     return bh
                               jbd2_journal_commit_transaction
                                 __jbd2_journal_refile_buffer
                                   __jbd2_journal_unfile_buffer
                                     __jbd2_journal_temp_unlink_buffer
  ext4_simulate_fail_bh()
    clear_buffer_uptodate
                                      mark_buffer_dirty
                                        <report warning>
                                        WARN_ON_ONCE(!buffer_uptodate(bh))

The best approach would be to perform fault injection in the IO completion
callback function, rather than after IO completion. However, the IO
completion callback function cannot get the fault injection code in sb.

Fix it by passing the result of fault injection into the bh read function,
we simulate faults within the bh read function itself. This requires adding
an extra parameter to the bh read functions that need fault injection.

Fixes: 46f870d690fe ("ext4: simulate various I/O and checksum errors when reading metadata")
Signed-off-by: Long Li <leo.lilong@huawei.com>
Link: https://patch.msgid.link/20240906091746.510163-1-leo.lilong@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Check buffer_verified in advance to avoid unneeded ext4_get_group_info().
This could be a simple cleanup as compiler may handle this.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://patch.msgid.link/20240820132234.2759926-8-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

If gdp from ext4_get_group_desc() is not NULL, then returned group_desc_bh
won't be NULL either. Remove check of group_desc_bh and only check
returned gdp from ext4_get_group_desc() like how other callers do.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://patch.msgid.link/20240820132234.2759926-7-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

There are some little improve:
1. remove repeat code to calculate checksum length of inode bitmap
2. remove unnecessary checksum length calculation if checksum is not
enabled.
3. use more efficient bit shift operation instead of div opreation.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://patch.msgid.link/20240820132234.2759926-6-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

If we can't grab any inode, the prvious find_inode_bit() will set ino
to be >= EXT4_INODES_PER_GROUP(sb). So the check of need to repeat
in the same group is not needed.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://patch.msgid.link/20240820132234.2759926-5-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

min_clusters is signed integer and will be converted to unsigned
integer when compared with unsigned number stats.free_clusters.
If min_clusters is negative, it will be converted to a huge unsigned
value in which case all groups may not meet the actual desired free
clusters.
Set negative min_clusters to 0 to avoid unexpected behavior.

Fixes: ac27a0ec112a ("[PATCH] ext4: initial copy of files from ext3")
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://patch.msgid.link/20240820132234.2759926-4-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

If a group is marked EXT4_GROUP_INFO_IBITMAP_CORRUPT after it's inode
bitmap buffer_head was successfully verified, then __ext4_new_inode()
will get a valid inode_bitmap_bh of a corrupted group from
ext4_read_inode_bitmap() in which case inode_bitmap_bh misses a release.
Hnadle "IS_ERR(inode_bitmap_bh)" and group corruption separately like
how ext4_free_inode() does to avoid buffer_head leak.

Fixes: 9008a58e5dce ("ext4: make the bitmap read routines return real error codes")
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://patch.msgid.link/20240820132234.2759926-3-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Release inode_bitmap_bh from ext4_read_inode_bitmap() in
ext4_mark_inode_used() to avoid buffer_head leak.
By the way, remove unneeded goto for invalid ino when inode_bitmap_bh
is NULL.

Fixes: 8016e29f4362 ("ext4: fast commit recovery path")
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://patch.msgid.link/20240820132234.2759926-2-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Call helper function ext4_update_inode_fsync_trans() instead of open
coding it in __ext4_new_inode().  This helper checks both that the handle
is valid *and* that it hasn't been aborted due to some fatal error in the
journalling layer, using is_handle_aborted().

Signed-off-by: Luis Henriques (SUSE) <luis.henriques@linux.dev>
Link: https://patch.msgid.link/20240527161447.21434-1-luis.henriques@linux.dev
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Convert to using the new inode timestamp accessor functions.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20231004185347.80880-33-jlayton@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>