ext4: remove alloc_semp

After taking care of all group init races, all that remains is to
remove alloc_semp from ext4_allocation_context and ext4_buddy structs.

Signed-off-by: Amir Goldstein <amir73il@users.sf.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

2 files changed, 1 insertions, 36 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 1816eafb0a05..254f1f9fc4eb 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1130,24 +1130,8 @@ ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
         e4b->bd_group = group;
         e4b->bd_buddy_page = NULL;
         e4b->bd_bitmap_page = NULL;
-        e4b->alloc_semp = &grp->alloc_sem;
-
-        /* Take the read lock on the group alloc
-         * sem. This would make sure a parallel
-         * ext4_mb_init_group happening on other
-         * groups mapped by the page is blocked
-         * till we are done with allocation
-         */
-repeat_load_buddy:
-        down_read(e4b->alloc_semp);
 
         if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
-                /* we need to check for group need init flag
-                 * with alloc_semp held so that we can be sure
-                 * that new blocks didn't get added to the group
-                 * when we are loading the buddy cache
-                 */
-                up_read(e4b->alloc_semp);
                 /*
                  * we need full data about the group
                  * to make a good selection
@@ -1155,7 +1139,6 @@ repeat_load_buddy:
                 ret = ext4_mb_init_group(sb, group);
                 if (ret)
                         return ret;
-                goto repeat_load_buddy;
         }
 
         /*
@@ -1247,9 +1230,6 @@ err:
                 page_cache_release(e4b->bd_buddy_page);
         e4b->bd_buddy = NULL;
         e4b->bd_bitmap = NULL;
-
-        /* Done with the buddy cache */
-        up_read(e4b->alloc_semp);
         return ret;
 }
 
@@ -1259,9 +1239,6 @@ static void ext4_mb_unload_buddy(struct ext4_buddy *e4b)
                 page_cache_release(e4b->bd_bitmap_page);
         if (e4b->bd_buddy_page)
                 page_cache_release(e4b->bd_buddy_page);
-        /* Done with the buddy cache */
-        if (e4b->alloc_semp)
-                up_read(e4b->alloc_semp);
 }
 
 
@@ -1574,9 +1551,6 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac,
         get_page(ac->ac_bitmap_page);
         ac->ac_buddy_page = e4b->bd_buddy_page;
         get_page(ac->ac_buddy_page);
-        /* on allocation we use ac to track the held semaphore */
-        ac->alloc_semp =  e4b->alloc_semp;
-        e4b->alloc_semp = NULL;
         /* store last allocated for subsequent stream allocation */
         if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) {
                 spin_lock(&sbi->s_md_lock);
@@ -4188,15 +4162,12 @@ static int ext4_mb_release_context(struct ext4_allocation_context *ac)
                         spin_unlock(&pa->pa_lock);
                 }
         }
-        if (ac->alloc_semp)
-                up_read(ac->alloc_semp);
         if (pa) {
                 /*
                  * We want to add the pa to the right bucket.
                  * Remove it from the list and while adding
                  * make sure the list to which we are adding
-                 * doesn't grow big.  We need to release
-                 * alloc_semp before calling ext4_mb_add_n_trim()
+                 * doesn't grow big.
                  */
                 if ((pa->pa_type == MB_GROUP_PA) && likely(pa->pa_free)) {
                         spin_lock(pa->pa_obj_lock);
diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index 22bd4d7f289b..20b5e7bfebd1 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -193,11 +193,6 @@ struct ext4_allocation_context {
         __u8 ac_op;             /* operation, for history only */
         struct page *ac_bitmap_page;
         struct page *ac_buddy_page;
-        /*
-         * pointer to the held semaphore upon successful
-         * block allocation
-         */
-        struct rw_semaphore *alloc_semp;
         struct ext4_prealloc_space *ac_pa;
         struct ext4_locality_group *ac_lg;
 };
@@ -215,7 +210,6 @@ struct ext4_buddy {
         struct super_block *bd_sb;
         __u16 bd_blkbits;
         ext4_group_t bd_group;
-        struct rw_semaphore *alloc_semp;
 };
 #define EXT4_MB_BITMAP(e4b)     ((e4b)->bd_bitmap)
 #define EXT4_MB_BUDDY(e4b)      ((e4b)->bd_buddy)