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>

4 files changed, 12 insertions, 1 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 386cb79ac4b6..1ae5004e93fc 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 09cdcd5914d0..655e760212b8 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 8d141a25bbee..4258d3289a6f 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 876e1c620365..511997ef6f0e 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);
         }