Gitweb:     http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=b5f10e...
Commit:     b5f10eed8125702929e57cca7e5956b1b9b6d015
Parent:     e29d1cde63be0b5f1739416b5574a83c34bf8eeb
Author:     Eric Sandeen <sandeen@redhat.com>
AuthorDate: Sat Aug 2 21:21:08 2008 -0400
Committer:  Theodore Ts'o <tytso@mit.edu>
CommitDate: Sat Aug 2 21:21:08 2008 -0400

    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: Eric Sandeen <sandeen@redhat.com>
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
 fs/ext4/balloc.c  |    3 +++
 fs/ext4/ialloc.c  |    5 ++++-
 fs/ext4/mballoc.c |    3 +++
 fs/ext4/super.c   |    2 ++
 4 files changed, 12 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 386cb79..1ae5004 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -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__,
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 09cdcd5..655e760 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -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 @@ got:
 
 			/* 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
 			 */
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 8d141a2..4258d32 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -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]);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 876e1c6..511997e 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -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);
 	}
--
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