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>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 1816eaf..254f1f9 100644 (file)
--- 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 22bd4d7..20b5e7b 100644 (file)
--- 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)