ext4: Use atomic_t's in struct flex_groups

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>

6 files changed, 30 insertions, 37 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index b37b12875582..53c72ad85877 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -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
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index e5c273ff928b..e52b48f86ed4 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -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 */
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 617f5a2d800a..5f393927fd25 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -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",
@@ -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");
@@ -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;
 
@@ -375,24 +374,24 @@ find_close_to_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:
@@ -960,9 +959,7 @@ got:
 
         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();
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index c4c430977622..e72c72a0b807 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -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);
@@ -4884,9 +4883,7 @@ do_more:
 
         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);
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index c06886abd658..546c7dd869e1 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -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);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 1ec554cc107a..6b5d5c6399fa 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -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;