2 files changed, 18 insertions, 3 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 7d7f6f91d555..0c7e247f714c 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1052,7 +1052,8 @@ static void ext4_mb_release_desc(struct ext4_buddy *e4b)
         if (e4b->bd_buddy_page)
                 page_cache_release(e4b->bd_buddy_page);
         /* Done with the buddy cache */
-        up_read(e4b->alloc_semp);
+        if (e4b->alloc_semp)
+                up_read(e4b->alloc_semp);
 }
 
 
@@ -1371,7 +1372,9 @@ 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_HINT_DATA)) {
                 spin_lock(&sbi->s_md_lock);
@@ -4289,6 +4292,7 @@ ext4_mb_initialize_context(struct ext4_allocation_context *ac,
         ac->ac_pa = NULL;
         ac->ac_bitmap_page = NULL;
         ac->ac_buddy_page = NULL;
+        ac->alloc_semp = NULL;
         ac->ac_lg = NULL;
 
         /* we have to define context: we'll we work with a file or
@@ -4469,6 +4473,8 @@ static int ext4_mb_release_context(struct ext4_allocation_context *ac)
                 }
                 ext4_mb_put_pa(ac, ac->ac_sb, pa);
         }
+        if (ac->alloc_semp)
+                up_read(ac->alloc_semp);
         if (ac->ac_bitmap_page)
                 page_cache_release(ac->ac_bitmap_page);
         if (ac->ac_buddy_page)
@@ -4569,10 +4575,14 @@ repeat:
                                 ac->ac_o_ex.fe_len < ac->ac_b_ex.fe_len)
                         ext4_mb_new_preallocation(ac);
         }
-
         if (likely(ac->ac_status == AC_STATUS_FOUND)) {
                 *errp = ext4_mb_mark_diskspace_used(ac, handle, reserv_blks);
                 if (*errp ==  -EAGAIN) {
+                        /*
+                         * drop the reference that we took
+                         * in ext4_mb_use_best_found
+                         */
+                        ext4_mb_release_context(ac);
                         ac->ac_b_ex.fe_group = 0;
                         ac->ac_b_ex.fe_start = 0;
                         ac->ac_b_ex.fe_len = 0;
diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index 95d4c7f29a8a..10a2921baf14 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -195,6 +195,11 @@ 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;
 };