From 08c3a8133810d955d97f7146c50c43e4073f2148 Mon Sep 17 00:00:00 2001 From: "Aneesh Kumar K.V" Date: Wed, 9 Sep 2009 23:50:17 -0400 Subject: ext4: Clarify the locking details in mballoc We don't need to take the alloc_sem lock when we are adding new groups, since mballoc won't see the new group added until we bump sbi->s_groups_count. Signed-off-by: "Theodore Ts'o" Signed-off-by: Aneesh Kumar K.V diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 484c9d1..d23056d 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -928,8 +928,11 @@ int ext4_mb_init_group(struct super_block *sb, ext4_group_t group) blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize; this_grp = ext4_get_group_info(sb, group); /* - * This ensures we don't add group - * to this buddy cache via resize + * This ensures that we don't reinit the buddy cache + * page which map to the group from which we are already + * allocating. If we are looking at the buddy cache we would + * have taken a reference using ext4_mb_load_buddy and that + * would have taken the alloc_sem lock. */ num_grp_locked = ext4_mb_get_buddy_cache_lock(sb, group); if (!EXT4_MB_GRP_NEED_INIT(this_grp)) { diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c index 68b0351..3cfc343 100644 --- a/fs/ext4/resize.c +++ b/fs/ext4/resize.c @@ -746,7 +746,6 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input) struct inode *inode = NULL; handle_t *handle; int gdb_off, gdb_num; - int num_grp_locked = 0; int err, err2; gdb_num = input->group / EXT4_DESC_PER_BLOCK(sb); @@ -856,7 +855,6 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input) * using the new disk blocks. */ - num_grp_locked = ext4_mb_get_buddy_cache_lock(sb, input->group); /* Update group descriptor block for new group */ gdp = (struct ext4_group_desc *)((char *)primary->b_data + gdb_off * EXT4_DESC_SIZE(sb)); @@ -875,10 +873,8 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input) * descriptor */ err = ext4_mb_add_groupinfo(sb, input->group, gdp); - if (err) { - ext4_mb_put_buddy_cache_lock(sb, input->group, num_grp_locked); + if (err) goto exit_journal; - } /* * Make the new blocks and inodes valid next. We do this before @@ -920,7 +916,6 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input) /* Update the global fs size fields */ sbi->s_groups_count++; - ext4_mb_put_buddy_cache_lock(sb, input->group, num_grp_locked); ext4_handle_dirty_metadata(handle, NULL, primary); -- cgit v0.10.2