[PATCH] ext4: fix sleep inside spinlock issue aka #14739

[Dmitry Monakhov <dmonakhov@openvz.org>]

drop i_block_reservation_lock before vfs_dq_reserve_block().
this patch fix http://bugzilla.kernel.org/show_bug.cgi?id=14739

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
 fs/ext4/inode.c |   29 ++++++++++++++++-------------
 1 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 942e183..f693768 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1852,19 +1852,8 @@ repeat:
 	md_needed = mdblocks - EXT4_I(inode)->i_reserved_meta_blocks;
 	total = md_needed + nrblocks;
 
-	/*
-	 * Make quota reservation here to prevent quota overflow
-	 * later. Real quota accounting is done at pages writeout
-	 * time.
-	 */
-	if (vfs_dq_reserve_block(inode, total)) {
-		spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
-		return -EDQUOT;
-	}
-
 	if (ext4_claim_free_blocks(sbi, total)) {
 		spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
-		vfs_dq_release_reservation_block(inode, total);
 		if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
 			yield();
 			goto repeat;
@@ -1872,10 +1861,24 @@ repeat:
 		return -ENOSPC;
 	}
 	EXT4_I(inode)->i_reserved_data_blocks += nrblocks;
-	EXT4_I(inode)->i_reserved_meta_blocks = mdblocks;
+	EXT4_I(inode)->i_reserved_meta_blocks += md_needed;
+	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
+
+	/*
+	 * Make quota reservation here to prevent quota overflow
+	 * later. Real quota accounting is done at pages writeout
+	 * time.
+	 */
+	if (!vfs_dq_reserve_block(inode, total))
+		return 0;       /* success */
 
+	/* Quota reservation has failed, revert inode's reservation */
+	percpu_counter_sub(&sbi->s_dirtyblocks_counter, total);
+	spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
+	EXT4_I(inode)->i_reserved_data_blocks -= nrblocks;
+	EXT4_I(inode)->i_reserved_meta_blocks -= md_needed;
 	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
-	return 0;       /* success */
+	return -EDQUOT;
 }
 
 static void ext4_da_release_space(struct inode *inode, int to_free)
-- 
1.6.0.4