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Commit b5f10eed authored by Eric Sandeen's avatar Eric Sandeen Committed by Theodore Ts'o
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ext4: lock block groups when initializing 



I noticed when filling a 1T filesystem with 4 threads using the
fs_mark benchmark:

fs_mark -d /mnt/test -D 256 -n 100000 -t 4 -s 20480 -F -S 0

that I occasionally got checksum mismatch errors:

EXT4-fs error (device sdb): ext4_init_inode_bitmap: Checksum bad for group 6935

etc.  I'd reliably get 4-5 of them during the run.

It appears that the problem is likely a race to init the bg's
when the uninit_bg feature is enabled.

With the patch below, which adds sb_bgl_locking around initialization,
I was able to complete several runs with no errors or warnings.

Signed-off-by: default avatarEric Sandeen <sandeen@redhat.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent e29d1cde

fs/ext4/balloc.c

+3 −0
Original line number Diff line number Diff line
@@ -321,12 +321,15 @@ ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group) 
	if (bh_uptodate_or_lock(bh))

		return bh;



	spin_lock(sb_bgl_lock(EXT4_SB(sb), block_group));

	if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {

		ext4_init_block_bitmap(sb, bh, block_group, desc);

		set_buffer_uptodate(bh);

		unlock_buffer(bh);

		spin_unlock(sb_bgl_lock(EXT4_SB(sb), block_group));

		return bh;

	}

	spin_unlock(sb_bgl_lock(EXT4_SB(sb), block_group));

	if (bh_submit_read(bh) < 0) {

		put_bh(bh);

		ext4_error(sb, __func__,

fs/ext4/ialloc.c

+4 −1
Original line number Diff line number Diff line
@@ -118,12 +118,15 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group) 
	if (bh_uptodate_or_lock(bh))

		return bh;



	spin_lock(sb_bgl_lock(EXT4_SB(sb), block_group));

	if (desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {

		ext4_init_inode_bitmap(sb, bh, block_group, desc);

		set_buffer_uptodate(bh);

		unlock_buffer(bh);

		spin_unlock(sb_bgl_lock(EXT4_SB(sb), block_group));

		return bh;

	}

	spin_unlock(sb_bgl_lock(EXT4_SB(sb), block_group));

	if (bh_submit_read(bh) < 0) {

		put_bh(bh);

		ext4_error(sb, __func__,
@@ -735,7 +738,7 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode * dir, int mode) 


			/* When marking the block group with

			 * ~EXT4_BG_INODE_UNINIT we don't want to depend

			 * on the value of bg_itable_unsed even though

			 * on the value of bg_itable_unused even though

			 * mke2fs could have initialized the same for us.

			 * Instead we calculated the value below

			 */

fs/ext4/mballoc.c

+3 −0
Original line number Diff line number Diff line
@@ -787,13 +787,16 @@ static int ext4_mb_init_cache(struct page *page, char *incore) 
		if (bh_uptodate_or_lock(bh[i]))

			continue;



		spin_lock(sb_bgl_lock(EXT4_SB(sb), first_group + i));

		if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {

			ext4_init_block_bitmap(sb, bh[i],

						first_group + i, desc);

			set_buffer_uptodate(bh[i]);

			unlock_buffer(bh[i]);

			spin_unlock(sb_bgl_lock(EXT4_SB(sb), first_group + i));

			continue;

		}

		spin_unlock(sb_bgl_lock(EXT4_SB(sb), first_group + i));

		get_bh(bh[i]);

		bh[i]->b_end_io = end_buffer_read_sync;

		submit_bh(READ, bh[i]);

fs/ext4/super.c

+2 −0
Original line number Diff line number Diff line
@@ -1621,6 +1621,7 @@ static int ext4_check_descriptors(struct super_block *sb) 
			       "(block %llu)!", i, inode_table);

			return 0;

		}

		spin_lock(sb_bgl_lock(sbi, i));

		if (!ext4_group_desc_csum_verify(sbi, i, gdp)) {

			printk(KERN_ERR "EXT4-fs: ext4_check_descriptors: "

			       "Checksum for group %lu failed (%u!=%u)\n",
@@ -1629,6 +1630,7 @@ static int ext4_check_descriptors(struct super_block *sb) 
			if (!(sb->s_flags & MS_RDONLY))

				return 0;

		}

		spin_unlock(sb_bgl_lock(sbi, i));

		if (!flexbg_flag)

			first_block += EXT4_BLOCKS_PER_GROUP(sb);

	}