linux-kernel - [PATCH 51/52] ext4: Don't allow nonextenst mount option for large filesystem

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Message-Id: <1215279378-30504-52-git-send-email-tytso@mit.edu>
Date:	Sat,  5 Jul 2008 13:36:17 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	Linux Kernel Developers List <linux-kernel@...r.kernel.org>
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Mingming Cao <cmm@...ibm.com>, "Theodore Ts'o" <tytso@....edu>
Subject: [PATCH 51/52] ext4: Don't allow nonextenst mount option for large filesystem

From: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>

The block mapped inode format can address only blocks within 2**32. This
causes a number of issues, the biggest of which is that the block
allocator needs to be taught that certain inodes can not utilize block
numbers > 2**32.  So until this is fixed, it is simplest to fail
mounting of file systems with more than 2**32 blocks if the -o noextents
option is given.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@...ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
 fs/ext4/super.c |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 4e104dd..2bf9cdd 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1004,6 +1004,7 @@ static int parse_options (char *options, struct super_block *sb,
 	int qtype, qfmt;
 	char *qname;
 #endif
+	ext4_fsblk_t last_block;
 
 	if (!options)
 		return 1;
@@ -1326,6 +1327,20 @@ set_qf_format:
 			set_opt (sbi->s_mount_opt, EXTENTS);
 			break;
 		case Opt_noextents:
+			/*
+			 * When e2fsprogs support resizing an already existing
+			 * ext3 file system to greater than 2**32 we need to
+			 * add support to block allocator to handle growing
+			 * already existing block  mapped inode so that blocks
+			 * allocated for them fall within 2**32
+			 */
+			last_block = ext4_blocks_count(sbi->s_es) - 1;
+			if (last_block  > 0xffffffffULL) {
+				printk(KERN_ERR "EXT4-fs: Filesystem too "
+						"large to mount with "
+						"-o noextents options\n");
+				return 0;
+			}
 			clear_opt (sbi->s_mount_opt, EXTENTS);
 			break;
 		case Opt_i_version:
-- 
1.5.6.rc3.1.g36b7.dirty

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