ext4: Don't allow new groups to be added during block allocation
After we mark the blocks in the buddy cache as allocated,
we need to ensure that we don't reinit the buddy cache until
the block bitmap is updated. This commit achieves this by holding
the group_info alloc_semaphore till ext4_mb_release_context
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 7d7f6f9..0c7e247 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1052,7 +1052,8 @@
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 @@
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 @@
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 @@
}
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 @@
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 95d4c7f..10a2921 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -195,6 +195,11 @@
__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;
};