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ext4: Use atomic_t's in struct flex_groups
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Reduce pressure on the sb_bgl_lock family of locks by using atomic_t's
to track the number of free blocks and inodes in each flex_group.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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Theodore Ts'o committed Mar 5, 2009
1 parent b713a5e commit 9f24e42
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Showing 6 changed files with 30 additions and 37 deletions.
5 changes: 2 additions & 3 deletions fs/ext4/balloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -470,9 +470,8 @@ void ext4_add_groupblocks(handle_t *handle, struct super_block *sb,

if (sbi->s_log_groups_per_flex) {
ext4_group_t flex_group = ext4_flex_group(sbi, block_group);
spin_lock(sb_bgl_lock(sbi, flex_group));
sbi->s_flex_groups[flex_group].free_blocks += blocks_freed;
spin_unlock(sb_bgl_lock(sbi, flex_group));
atomic_add(blocks_freed,
&sbi->s_flex_groups[flex_group].free_blocks);
}
/*
* request to reload the buddy with the
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4 changes: 2 additions & 2 deletions fs/ext4/ext4.h
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Original file line number Diff line number Diff line change
Expand Up @@ -170,8 +170,8 @@ struct ext4_group_desc
*/

struct flex_groups {
__u32 free_inodes;
__u32 free_blocks;
atomic_t free_inodes;
atomic_t free_blocks;
};

#define EXT4_BG_INODE_UNINIT 0x0001 /* Inode table/bitmap not in use */
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33 changes: 15 additions & 18 deletions fs/ext4/ialloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,6 @@ void ext4_free_inode(handle_t *handle, struct inode *inode)
struct ext4_super_block *es;
struct ext4_sb_info *sbi;
int fatal = 0, err, count, cleared;
ext4_group_t flex_group;

if (atomic_read(&inode->i_count) > 1) {
printk(KERN_ERR "ext4_free_inode: inode has count=%d\n",
Expand Down Expand Up @@ -277,10 +276,10 @@ void ext4_free_inode(handle_t *handle, struct inode *inode)
percpu_counter_dec(&sbi->s_dirs_counter);

if (sbi->s_log_groups_per_flex) {
flex_group = ext4_flex_group(sbi, block_group);
spin_lock(sb_bgl_lock(sbi, flex_group));
sbi->s_flex_groups[flex_group].free_inodes++;
spin_unlock(sb_bgl_lock(sbi, flex_group));
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");
Expand Down Expand Up @@ -360,9 +359,9 @@ static int find_group_flex(struct super_block *sb, struct inode *parent,
sbi->s_log_groups_per_flex;

find_close_to_parent:
flexbg_free_blocks = flex_group[best_flex].free_blocks;
flexbg_free_blocks = atomic_read(&flex_group[best_flex].free_blocks);
flex_freeb_ratio = flexbg_free_blocks * 100 / blocks_per_flex;
if (flex_group[best_flex].free_inodes &&
if (atomic_read(&flex_group[best_flex].free_inodes) &&
flex_freeb_ratio > free_block_ratio)
goto found_flexbg;

Expand All @@ -375,24 +374,24 @@ static int find_group_flex(struct super_block *sb, struct inode *parent,
if (i == parent_fbg_group || i == parent_fbg_group - 1)
continue;

flexbg_free_blocks = flex_group[i].free_blocks;
flexbg_free_blocks = atomic_read(&flex_group[i].free_blocks);
flex_freeb_ratio = flexbg_free_blocks * 100 / blocks_per_flex;

if (flex_freeb_ratio > free_block_ratio &&
flex_group[i].free_inodes) {
(atomic_read(&flex_group[i].free_inodes))) {
best_flex = i;
goto found_flexbg;
}

if (flex_group[best_flex].free_inodes == 0 ||
(flex_group[i].free_blocks >
flex_group[best_flex].free_blocks &&
flex_group[i].free_inodes))
if ((atomic_read(&flex_group[best_flex].free_inodes) == 0) ||
((atomic_read(&flex_group[i].free_blocks) >
atomic_read(&flex_group[best_flex].free_blocks)) &&
atomic_read(&flex_group[i].free_inodes)))
best_flex = i;
}

if (!flex_group[best_flex].free_inodes ||
!flex_group[best_flex].free_blocks)
if (!atomic_read(&flex_group[best_flex].free_inodes) ||
!atomic_read(&flex_group[best_flex].free_blocks))
return -1;

found_flexbg:
Expand Down Expand Up @@ -960,9 +959,7 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode)

if (sbi->s_log_groups_per_flex) {
flex_group = ext4_flex_group(sbi, group);
spin_lock(sb_bgl_lock(sbi, flex_group));
sbi->s_flex_groups[flex_group].free_inodes--;
spin_unlock(sb_bgl_lock(sbi, flex_group));
atomic_dec(&sbi->s_flex_groups[flex_group].free_inodes);
}

inode->i_uid = current_fsuid();
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9 changes: 3 additions & 6 deletions fs/ext4/mballoc.c
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Expand Up @@ -3044,9 +3044,8 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
if (sbi->s_log_groups_per_flex) {
ext4_group_t flex_group = ext4_flex_group(sbi,
ac->ac_b_ex.fe_group);
spin_lock(sb_bgl_lock(sbi, flex_group));
sbi->s_flex_groups[flex_group].free_blocks -= ac->ac_b_ex.fe_len;
spin_unlock(sb_bgl_lock(sbi, flex_group));
atomic_sub(ac->ac_b_ex.fe_len,
&sbi->s_flex_groups[flex_group].free_blocks);
}

err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
Expand Down Expand Up @@ -4884,9 +4883,7 @@ void ext4_mb_free_blocks(handle_t *handle, struct inode *inode,

if (sbi->s_log_groups_per_flex) {
ext4_group_t flex_group = ext4_flex_group(sbi, block_group);
spin_lock(sb_bgl_lock(sbi, flex_group));
sbi->s_flex_groups[flex_group].free_blocks += count;
spin_unlock(sb_bgl_lock(sbi, flex_group));
atomic_add(count, &sbi->s_flex_groups[flex_group].free_blocks);
}

ext4_mb_release_desc(&e4b);
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8 changes: 4 additions & 4 deletions fs/ext4/resize.c
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Original file line number Diff line number Diff line change
Expand Up @@ -938,10 +938,10 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
ext4_group_t flex_group;
flex_group = ext4_flex_group(sbi, input->group);
sbi->s_flex_groups[flex_group].free_blocks +=
input->free_blocks_count;
sbi->s_flex_groups[flex_group].free_inodes +=
EXT4_INODES_PER_GROUP(sb);
atomic_add(input->free_blocks_count,
&sbi->s_flex_groups[flex_group].free_blocks);
atomic_add(EXT4_INODES_PER_GROUP(sb),
&sbi->s_flex_groups[flex_group].free_inodes);
}

ext4_handle_dirty_metadata(handle, NULL, sbi->s_sbh);
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8 changes: 4 additions & 4 deletions fs/ext4/super.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1630,10 +1630,10 @@ static int ext4_fill_flex_info(struct super_block *sb)
gdp = ext4_get_group_desc(sb, i, &bh);

flex_group = ext4_flex_group(sbi, i);
sbi->s_flex_groups[flex_group].free_inodes +=
ext4_free_inodes_count(sb, gdp);
sbi->s_flex_groups[flex_group].free_blocks +=
ext4_free_blks_count(sb, gdp);
atomic_set(&sbi->s_flex_groups[flex_group].free_inodes,
ext4_free_inodes_count(sb, gdp));
atomic_set(&sbi->s_flex_groups[flex_group].free_blocks,
ext4_free_blks_count(sb, gdp));
}

return 1;
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