linux-ext4 - [PATCH] ext4: BUG_ON triggered in ext4_mb_complex_scan

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Date:	Mon, 5 Apr 2010 12:30:19 +0800
From:	jing zhang <zj.barak@...il.com>
To:	linux-ext4 <linux-ext4@...r.kernel.org>
Cc:	"Theodore Ts'o" <tytso@....edu>,
	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Andreas Dilger <adilger@....com>,
	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
Subject: [PATCH] ext4: BUG_ON triggered in ext4_mb_complex_scan_group()

From: Jing Zhang <zj.barak@...il.com>

Date: Mon Apr 5 12:10:50     2010

BUG_ON is triggered at [line:1762] in ext4_mb_complex_scan_group(),
and fix is to change the return value of mb_find_extent() if the
needed extent can not be found. The fix can also be applied to other
points where mb_find_extent() is called.

Cc: Theodore Ts'o <tytso@....edu>
Cc: Andreas Dilger <adilger@....com>
Cc: Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
Cc: "Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
Signed-off-by: Jing Zhang <zj.barak@...il.com>
---
 fs/ext4/mballoc.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index bba1282..fbb6899 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1321,7 +1321,7 @@ static int mb_find_extent(struct ext4_buddy
*e4b, int order, int block,
 		ex->fe_len = 0;
 		ex->fe_start = 0;
 		ex->fe_group = 0;
-		return 0;
+		return -ENOSPC;
 	}

 	/* FIXME dorp order completely ? */
@@ -1358,6 +1358,8 @@ static int mb_find_extent(struct ext4_buddy
*e4b, int order, int block,
 	}

 	BUG_ON(ex->fe_start + ex->fe_len > (1 << (e4b->bd_blkbits + 3)));
+	if (needed > ex->fe_len)
+		return -ENOSPC;
 	return ex->fe_len;
 }

@@ -1758,7 +1760,8 @@ void ext4_mb_complex_scan_group(struct
ext4_allocation_context *ac,
 			break;
 		}

-		mb_find_extent(e4b, 0, i, ac->ac_g_ex.fe_len, &ex);
+		if (0 > mb_find_extent(e4b, 0, i, ac->ac_g_ex.fe_len, &ex))
+			break;
 		BUG_ON(ex.fe_len <= 0);
 		if (free < ex.fe_len) {
 			ext4_grp_locked_error(sb, e4b->bd_group,
--
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