[PATCH] fix ext3 mounts at 16T
I need to do some actual IO testing now, but this gets things mounting for
a 16T ext3 filesystem. (patched up e2fsprogs is needed too, I'll send that
off the kernel list)
This patch fixes these issues in the kernel:
o sbi->s_groups_count overflows in ext3_fill_super()
sbi->s_groups_count = (le32_to_cpu(es->s_blocks_count) -
le32_to_cpu(es->s_first_data_block) +
EXT3_BLOCKS_PER_GROUP(sb) - 1) /
EXT3_BLOCKS_PER_GROUP(sb);
at 16T, s_blocks_count is already maxed out; adding
EXT3_BLOCKS_PER_GROUP(sb) overflows it and groups_count comes out to 0.
Not really what we want, and causes a failed mount.
Feel free to check my math (actually, please do!), but changing it this
way should work & avoid the overflow:
(A + B - 1)/B changed to: ((A - 1)/B) + 1
o ext3_check_descriptors() overflows range checks
ext3_check_descriptors() iterates over all block groups making sure
that various bits are within the right block ranges... on the last pass
through, it is checking the error case
[item] >= block + EXT3_BLOCKS_PER_GROUP(sb)
where "block" is the first block in the last block group. The last
block in this group (and the last one that will fit in 32 bits) is block
+ EXT3_BLOCKS_PER_GROUP(sb)- 1. block + EXT3_BLOCKS_PER_GROUP(sb) wraps
back around to 0.
so, make things clearer with "first_block" and "last_block" where those
are first and last, inclusive, and use <, > rather than <, >=.
Finally, the last block group may be smaller than the rest, so account
for this on the last pass through: last_block = sb->s_blocks_count - 1;
(a similar patch could be done for ext2; does anyone in their right mind
use ext2 at 16T? I'll send an ext2 patch doing the same thing if that's
warranted)
Signed-off-by: Eric Sandeen <esandeen@redhat.com>
Cc: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
1 file changed