Re: [PATCH -V5] ext4: fix BUG when calling ext4_error with locked block group

Mingming Cao
2008-12-02T22:47:43Z

在 2008-12-02二的 11:39 +0530，Aneesh Kumar K.V写道：
> The mballoc code likes to call ext4_error while it is holding locked
> block groups. This can causes a scheduling in atomic context BUG. We
> can't just unlock the block group and relock it after/if ext4_error
> returns since that might result in race conditions in the case where
> the filesystem is set to continue after finding errors.
>
> -V5 changes:
> update ext4_commit_super to use the percpu free blocks and free inodes
> counter values.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
> ---
> fs/ext4/ext4.h | 47 +++++++++++++++++++++++++++++++++++++++++++++++
> fs/ext4/mballoc.c | 30 +++++++++++++++---------------
> fs/ext4/mballoc.h | 47 -----------------------------------------------
> fs/ext4/super.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
> 4 files changed, 105 insertions(+), 64 deletions(-)

> void ext4_update_dynamic_rev(struct super_block *sb)
> {
> struct ext4_super_block *es = EXT4_SB(sb)->s_es;
> @@ -2820,8 +2858,11 @@ static void ext4_commit_super(struct super_block *sb,
> set_buffer_uptodate(sbh);
> }
> es->s_wtime = cpu_to_le32(get_seconds());
> - ext4_free_blocks_count_set(es, ext4_count_free_blocks(sb));
> - es->s_free_inodes_count = cpu_to_le32(ext4_count_free_inodes(sb));
> + ext4_free_blocks_count_set(es, percpu_counter_sum_positive(
> + &EXT4_SB(sb)->s_freeblocks_counter));
> + es->s_free_inodes_count = cpu_to_le32(percpu_counter_sum_positive(
> + &EXT4_SB(sb)->s_freeinodes_counter));
> +
> BUFFER_TRACE(sbh, "marking dirty");
> mark_buffer_dirty(sbh);
> if (sync) {

I thought the per cpu s_freeblocks_counter is not as accurate as the sum
of group free blocks counters, we are depending on
ext4_count_free_blocks() to gets the accurate free blocks counter
flushed to disk...

Mingming

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