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Subject[PATCH 51/52] ext4: Don't allow nonextenst mount option for large filesystem
Date
From: Aneesh Kumar K.V <aneesh.kumar@linux.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@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.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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