linux-ext4 - [PATCH -V2 3/5] ext4: Fix the race between read_block_bitmap and mark_diskspace

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Date:	Fri, 21 Nov 2008 22:14:33 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	cmm@...ibm.com, tytso@....edu, sandeen@...hat.com
Cc:	linux-ext4@...r.kernel.org,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH -V2 3/5] ext4: Fix the race between read_block_bitmap and mark_diskspace_used

We need to make sure we update the block bitmap and clear
EXT4_BG_BLOCK_UNINIT flag with sb_bgl_lock held. We look
at EXT4_BG_BLOCK_UNINIT and reinit the block bitmap each
time in ext4_read_block_bitmap (introduced by
c806e68f5647109350ec546fee5b526962970fd2 )

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
 fs/ext4/mballoc.c |   17 ++++++++++++-----
 1 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index c5dcdf0..1ed949c 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1065,6 +1065,8 @@ static void mb_clear_bits(spinlock_t *lock, void *bm, int cur, int len)
 	__u32 *addr;
 
 	len = cur + len;
+	if (lock)
+		spin_lock(lock);			\
 	while (cur < len) {
 		if ((cur & 31) == 0 && (len - cur) >= 32) {
 			/* fast path: clear whole word at once */
@@ -1073,9 +1075,11 @@ static void mb_clear_bits(spinlock_t *lock, void *bm, int cur, int len)
 			cur += 32;
 			continue;
 		}
-		mb_clear_bit_atomic(lock, cur, bm);
+		mb_clear_bit(cur, bm);
 		cur++;
 	}
+	if (lock)
+		spin_unlock(lock);			\
 }
 
 static void mb_set_bits(spinlock_t *lock, void *bm, int cur, int len)
@@ -1083,6 +1087,8 @@ static void mb_set_bits(spinlock_t *lock, void *bm, int cur, int len)
 	__u32 *addr;
 
 	len = cur + len;
+	if (lock)
+		spin_lock(lock);			\
 	while (cur < len) {
 		if ((cur & 31) == 0 && (len - cur) >= 32) {
 			/* fast path: set whole word at once */
@@ -1091,9 +1097,11 @@ static void mb_set_bits(spinlock_t *lock, void *bm, int cur, int len)
 			cur += 32;
 			continue;
 		}
-		mb_set_bit_atomic(lock, cur, bm);
+		mb_set_bit(cur, bm);
 		cur++;
 	}
+	if (lock)
+		spin_unlock(lock);			\
 }
 
 static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
@@ -3004,10 +3012,9 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
 		}
 	}
 #endif
-	mb_set_bits(sb_bgl_lock(sbi, ac->ac_b_ex.fe_group), bitmap_bh->b_data,
-				ac->ac_b_ex.fe_start, ac->ac_b_ex.fe_len);
-
 	spin_lock(sb_bgl_lock(sbi, ac->ac_b_ex.fe_group));
+	mb_set_bits(NULL, bitmap_bh->b_data,
+				ac->ac_b_ex.fe_start, ac->ac_b_ex.fe_len);
 	if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
 		gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
 		gdp->bg_free_blocks_count =
-- 
1.6.0.4.735.gea4f

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