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Date: Sat, 17 Apr 2010 14:57:22 +0400
From: Dmitry Monakhov <dmonakhov@...nvz.org>
To: tytso@....edu
Cc: linux-ext4@...r.kernel.org, jack@...e.cz
Subject: Re: [PATCH 2/2] ext4: fix inode bitmaps manipulation in free_inode
tytso@....edu writes:
> Here's my -V3 respin of this patch, which further cleans up the code
> and removes some duplicated code by only calling ext4_clear_bit() from
> one call site.
>
> I think I'm about done for this, so if you agree with my improvements
> as improvements, it might be useful to port this back to ext3 version
> of this patch.
Ok, agree that's looks better.
>
> - Ted
>
> ext4: clean up inode bitmaps manipulation in ext4_free_inode
>
> From: Dmitry Monakhov <dmonakhov@...nvz.org>
>
> - Reorganize locking scheme to batch two atomic operation in to one.
> This also allow us to state what healthy group must obey following rule
> ext4_free_inodes_count(sb, gdp) == ext4_count_free(inode_bitmap, NUM);
> - Fix possible undefined pointer dereference.
> - Even if group descriptor stats aren't accessible we have to update
> inode bitmaps.
> - Move non-group members update out of group_lock.
>
> Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> ---
> fs/ext4/ialloc.c | 81 ++++++++++++++++++++++++-----------------------------
> 1 files changed, 37 insertions(+), 44 deletions(-)
>
> diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
> index 57f6eef..52618d5 100644
> --- a/fs/ext4/ialloc.c
> +++ b/fs/ext4/ialloc.c
> @@ -240,56 +240,49 @@ void ext4_free_inode(handle_t *handle, struct inode *inode)
> if (fatal)
> goto error_return;
>
> - /* Ok, now we can actually update the inode bitmaps.. */
> - cleared = ext4_clear_bit_atomic(ext4_group_lock_ptr(sb, block_group),
> - bit, bitmap_bh->b_data);
> - if (!cleared)
> - ext4_error(sb, "bit already cleared for inode %lu", ino);
> - else {
> - gdp = ext4_get_group_desc(sb, block_group, &bh2);
> -
> + fatal = -ESRCH;
> + gdp = ext4_get_group_desc(sb, block_group, &bh2);
> + if (gdp) {
> BUFFER_TRACE(bh2, "get_write_access");
> fatal = ext4_journal_get_write_access(handle, bh2);
> - if (fatal) goto error_return;
> -
> - if (gdp) {
> - ext4_lock_group(sb, block_group);
> - count = ext4_free_inodes_count(sb, gdp) + 1;
> - ext4_free_inodes_set(sb, gdp, count);
> - if (is_directory) {
> - count = ext4_used_dirs_count(sb, gdp) - 1;
> - ext4_used_dirs_set(sb, gdp, count);
> - if (sbi->s_log_groups_per_flex) {
> - ext4_group_t f;
> -
> - f = ext4_flex_group(sbi, block_group);
> - atomic_dec(&sbi->s_flex_groups[f].used_dirs);
> - }
> + }
> + ext4_lock_group(sb, block_group);
> + cleared = ext4_clear_bit(bit, bitmap_bh->b_data);
> + if (fatal || !cleared) {
> + ext4_unlock_group(sb, block_group);
> + goto out;
> + }
>
> - }
> - gdp->bg_checksum = ext4_group_desc_csum(sbi,
> - block_group, gdp);
> - ext4_unlock_group(sb, block_group);
> - percpu_counter_inc(&sbi->s_freeinodes_counter);
> - if (is_directory)
> - percpu_counter_dec(&sbi->s_dirs_counter);
> -
> - if (sbi->s_log_groups_per_flex) {
> - ext4_group_t f;
> -
> - f = ext4_flex_group(sbi, block_group);
> - atomic_inc(&sbi->s_flex_groups[f].free_inodes);
> - }
> - }
> - BUFFER_TRACE(bh2, "call ext4_handle_dirty_metadata");
> - err = ext4_handle_dirty_metadata(handle, NULL, bh2);
> - if (!fatal) fatal = err;
> + count = ext4_free_inodes_count(sb, gdp) + 1;
> + ext4_free_inodes_set(sb, gdp, count);
> + if (is_directory) {
> + count = ext4_used_dirs_count(sb, gdp) - 1;
> + ext4_used_dirs_set(sb, gdp, count);
> + percpu_counter_dec(&sbi->s_dirs_counter);
> }
> - BUFFER_TRACE(bitmap_bh, "call ext4_handle_dirty_metadata");
> - err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
> - if (!fatal)
> - fatal = err;
> - sb->s_dirt = 1;
> + gdp->bg_checksum = ext4_group_desc_csum(sbi, block_group, gdp);
> + ext4_unlock_group(sb, block_group);
> +
> + percpu_counter_inc(&sbi->s_freeinodes_counter);
> + if (sbi->s_log_groups_per_flex) {
> + ext4_group_t f = ext4_flex_group(sbi, block_group);
> +
> + atomic_inc(&sbi->s_flex_groups[f].free_inodes);
> + if (is_directory)
> + atomic_dec(&sbi->s_flex_groups[f].used_dirs);
> + }
> + BUFFER_TRACE(bh2, "call ext4_handle_dirty_metadata");
> + fatal = ext4_handle_dirty_metadata(handle, NULL, bh2);
> +out:
> + if (cleared) {
> + BUFFER_TRACE(bitmap_bh, "call ext4_handle_dirty_metadata");
> + err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
> + if (!fatal)
> + fatal = err;
> + sb->s_dirt = 1;
> + } else
> + ext4_error(sb, "bit already cleared for inode %lu", ino);
> +
> error_return:
> brelse(bitmap_bh);
> ext4_std_error(sb, fatal);
--
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