3.5.1 ext4_ sleeping while atomic bug.

3.5.1 ext4_ sleeping while atomic bug.

[Dave Jones]

BUG: sleeping function called from invalid context at include/linux/buffer_head.h:333
in_atomic(): 1, irqs_disabled(): 0, pid: 9894, name: fstest
3 locks held by fstest/9894:
 #0:  (&type->i_mutex_dir_key#4/1){+.+.+.}, at: [<ffffffff811d5dae>] kern_path_create+0x7e/0x140
 #1:  (&ei->i_data_sem){++++..}, at: [<ffffffff81252e76>] ext4_map_blocks+0xb6/0x250
 #2:  (&(&bgl->locks[i].lock)->rlock){+.+...}, at: [<ffffffff8124a5e7>] ext4_validate_block_bitmap+0x77/0x230
Pid: 9894, comm: fstest Not tainted 3.5.1-1.fc17.x86_64.debug #1
Call Trace:
 [<ffffffff8109cd0a>] __might_sleep+0x18a/0x240
 [<ffffffff811fb430>] __sync_dirty_buffer+0x30/0xf0
 [<ffffffff811fb503>] sync_dirty_buffer+0x13/0x20
 [<ffffffff81273018>] ext4_commit_super+0x1e8/0x260
 [<ffffffff81273283>] save_error_info+0x23/0x30
 [<ffffffff81274539>] __ext4_error+0x89/0xa0
 [<ffffffff8124a5e7>] ? ext4_validate_block_bitmap+0x77/0x230
 [<ffffffff8124a72b>] ext4_validate_block_bitmap+0x1bb/0x230
 [<ffffffff8124b0ae>] ext4_read_block_bitmap_nowait+0x8e/0x3b0
 [<ffffffff812891c0>] ext4_mb_init_cache+0x160/0x990
 [<ffffffff810d16bd>] ? trace_hardirqs_on_caller+0x10d/0x1a0
 [<ffffffff81289b16>] ext4_mb_init_group+0x126/0x250
 [<ffffffff81289d56>] ext4_mb_good_group+0x116/0x130
 [<ffffffff8128c493>] ext4_mb_regular_allocator+0x1a3/0x420
 [<ffffffff811aa920>] ? kmem_cache_alloc+0xe0/0x290
 [<ffffffff8128e2c1>] ext4_mb_new_blocks+0x4f1/0xb90
 [<ffffffff811fad9f>] ? __find_get_block+0xaf/0x220
 [<ffffffff81293e7e>] ext4_alloc_branch+0x42e/0x690
 [<ffffffff816c6030>] ? _raw_spin_unlock_irq+0x30/0x50
 [<ffffffff812949a7>] ext4_ind_map_blocks+0x1e7/0x990
 [<ffffffff816c348a>] ? down_write+0x9a/0xb0
 [<ffffffff81252e76>] ? ext4_map_blocks+0xb6/0x250
 [<ffffffff81252ea5>] ext4_map_blocks+0xe5/0x250
 [<ffffffff8125306b>] ext4_getblk+0x5b/0x1f0
 [<ffffffff81253218>] ext4_bread+0x18/0xa0
 [<ffffffff8125e527>] ext4_mkdir+0x147/0x3d0
 [<ffffffff811d2536>] vfs_mkdir+0xa6/0x130
 [<ffffffff811d6c6e>] sys_mkdirat+0xbe/0xd0
 [<ffffffff811d6c99>] sys_mkdir+0x19/0x20
 [<ffffffff816cefe9>] system_call_fastpath+0x16/0x1b

Re: 3.5.1 ext4_ sleeping while atomic bug.

[Theodore Ts'o]

Hi Dave,

Thanks for the bug report!  The following should address the bug which
you found.

						- Ted

>From 05ca87aa00121756b5d41f3d71eb8b51bed3bc92 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@mit.edu>
Date: Fri, 10 Aug 2012 13:57:52 -0400
Subject: [PATCH] ext4: don't call ext4_error while block group is locked

While in ext4_validate_block_bitmap(), if an block allocation bitmap
is found to be invalid, we call ext4_error() while the block group is
still locked.  This causes ext4_commit_super() to call a function
which might sleep while in an atomic context.

There's no need to keep the block group locked at this point, so hoist
the ext4_error() call up to ext4_validate_block_bitmap() and release
the block group spinlock before calling ext4_error().

The reported stack trace can be found at:

	http://article.gmane.org/gmane.comp.file-systems.ext4/33731

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
---
 fs/ext4/balloc.c | 62 +++++++++++++++++++++++++++++++++-----------------------
 fs/ext4/bitmap.c |  1 -
 2 files changed, 37 insertions(+), 26 deletions(-)

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index d23b31c..1b50890 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -280,14 +280,18 @@ struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
 	return desc;
 }
 
-static int ext4_valid_block_bitmap(struct super_block *sb,
-				   struct ext4_group_desc *desc,
-				   unsigned int block_group,
-				   struct buffer_head *bh)
+/*
+ * Return the block number which was discovered to be invalid, or 0 if
+ * the block bitmap is valid.
+ */
+static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb,
+					    struct ext4_group_desc *desc,
+					    unsigned int block_group,
+					    struct buffer_head *bh)
 {
 	ext4_grpblk_t offset;
 	ext4_grpblk_t next_zero_bit;
-	ext4_fsblk_t bitmap_blk;
+	ext4_fsblk_t blk;
 	ext4_fsblk_t group_first_block;
 
 	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
@@ -297,37 +301,33 @@ static int ext4_valid_block_bitmap(struct super_block *sb,
 		 * or it has to also read the block group where the bitmaps
 		 * are located to verify they are set.
 		 */
-		return 1;
+		return 0;
 	}
 	group_first_block = ext4_group_first_block_no(sb, block_group);
 
 	/* check whether block bitmap block number is set */
-	bitmap_blk = ext4_block_bitmap(sb, desc);
-	offset = bitmap_blk - group_first_block;
+	blk = ext4_block_bitmap(sb, desc);
+	offset = blk - group_first_block;
 	if (!ext4_test_bit(offset, bh->b_data))
 		/* bad block bitmap */
-		goto err_out;
+		return blk;
 
 	/* check whether the inode bitmap block number is set */
-	bitmap_blk = ext4_inode_bitmap(sb, desc);
-	offset = bitmap_blk - group_first_block;
+	blk = ext4_inode_bitmap(sb, desc);
+	offset = blk - group_first_block;
 	if (!ext4_test_bit(offset, bh->b_data))
 		/* bad block bitmap */
-		goto err_out;
+		return blk;
 
 	/* check whether the inode table block number is set */
-	bitmap_blk = ext4_inode_table(sb, desc);
-	offset = bitmap_blk - group_first_block;
+	blk = ext4_inode_table(sb, desc);
+	offset = blk - group_first_block;
 	next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
 				offset + EXT4_SB(sb)->s_itb_per_group,
 				offset);
-	if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
-		/* good bitmap for inode tables */
-		return 1;
-
-err_out:
-	ext4_error(sb, "Invalid block bitmap - block_group = %d, block = %llu",
-			block_group, bitmap_blk);
+	if (next_zero_bit < offset + EXT4_SB(sb)->s_itb_per_group)
+		/* bad bitmap for inode tables */
+		return blk;
 	return 0;
 }
 
@@ -336,14 +336,26 @@ void ext4_validate_block_bitmap(struct super_block *sb,
 			       unsigned int block_group,
 			       struct buffer_head *bh)
 {
+	ext4_fsblk_t	blk;
+
 	if (buffer_verified(bh))
 		return;
 
 	ext4_lock_group(sb, block_group);
-	if (ext4_valid_block_bitmap(sb, desc, block_group, bh) &&
-	    ext4_block_bitmap_csum_verify(sb, block_group, desc, bh,
-					  EXT4_BLOCKS_PER_GROUP(sb) / 8))
-		set_buffer_verified(bh);
+	blk = ext4_valid_block_bitmap(sb, desc, block_group, bh);
+	if (unlikely(blk != 0)) {
+		ext4_unlock_group(sb, block_group);
+		ext4_error(sb, "bg %u: block %llu: invalid block bitmap",
+			   block_group, blk);
+		return;
+	}
+	if (unlikely(!ext4_block_bitmap_csum_verify(sb, block_group,
+			desc, bh, EXT4_BLOCKS_PER_GROUP(sb) / 8))) {
+		ext4_unlock_group(sb, block_group);
+		ext4_error(sb, "bg %u: bad block bitmap checksum", block_group);
+		return;
+	}
+	set_buffer_verified(bh);
 	ext4_unlock_group(sb, block_group);
 }
 
diff --git a/fs/ext4/bitmap.c b/fs/ext4/bitmap.c
index f8716ea..5c2d181 100644
--- a/fs/ext4/bitmap.c
+++ b/fs/ext4/bitmap.c
@@ -79,7 +79,6 @@ int ext4_block_bitmap_csum_verify(struct super_block *sb, ext4_group_t group,
 	if (provided == calculated)
 		return 1;
 
-	ext4_error(sb, "Bad block bitmap checksum: block_group = %u", group);
 	return 0;
 }
 
-- 
1.7.12.rc0.22.gcdd159b