Commit f41c0750 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Theodore Ts'o
Browse files

ext4: check for need init flag in ext4_mb_load_buddy 



We should check for need init flag with the group's alloc_sem held, to
make sure while we are loading the buddy cache and holding a reference
to it, a file system resize can't add new blocks to same group.

The patch also drops the need init flag check in
ext4_mb_regular_allocator() because doing the check without holding
alloc_sem is racy.

Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
parent b6a758ec

fs/ext4/mballoc.c

+18 −21
Original line number Diff line number Diff line
@@ -1034,8 +1034,26 @@ ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group, 
	 * 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

		 */

		ret = ext4_mb_init_group(sb, group);

		if (ret)

			return ret;

		goto repeat_load_buddy;

	}



	/*

	 * the buddy cache inode stores the block bitmap

	 * and buddy information in consecutive blocks.
@@ -2012,27 +2030,6 @@ repeat: 
			if (grp->bb_free == 0)

				continue;



			/*

			 * if the group is already init we check whether it is

			 * a good group and if not we don't load the buddy

			 */

			if (EXT4_MB_GRP_NEED_INIT(grp)) {

				/*

				 * we need full data about the group

				 * to make a good selection

				 */

				err = ext4_mb_init_group(sb, group);

				if (err)

					goto out;

			}



			/*

			 * If the particular group doesn't satisfy our

			 * criteria we continue with the next group

			 */

			if (!ext4_mb_good_group(ac, group, cr))

				continue;



			err = ext4_mb_load_buddy(sb, group, &e4b);

			if (err)

				goto out;

CRA Git | Maintained and supported by SUSTech CRA and CCSE