lkml.org 
[lkml]   [2008]   [Dec]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [Patch/BUG] (ext4) s_mb_maxs[] of ext4_sb_info is too small size
    > Yasunori Goto wrote:
    > > Hello.
    > >
    > > I chased the cause of following ext4 oops report which is tested on
    > > ia64 box.
    > >
    > > http://bugzilla.kernel.org/show_bug.cgi?id=12018
    > >
    > > The cause is the size of s_mb_maxs array that is
    > > defined as "unsigned short" in ext4_sb_info structure.
    > > Unsigned short is too small.
    > >
    > > In this bug report, Li-san formatted with 64Kbyte block size like
    > > the following. Ia64 has 64Kbyte page size, then this
    > > block size is acceptable.
    > >
    > > # mkfs.ext4 -b 65536 /dev/md0
    > >
    > > In this case, the maximum value of s_mb_maxs[] becomes
    > > (blocksize << 2) = 256K by the following code.
    > >
    > > 2482 int ext4_mb_init(struct super_block *sb, int needs_recovery)
    > > :
    > > :
    > > 2508 max = sb->s_blocksize << 2; <---- max becomes 0x40000.
    > > 2509 do {
    > > 2510 sbi->s_mb_offsets[i] = offset;
    > > 2511 sbi->s_mb_maxs[i] = max; <--- over flow!!!
    > > 2512 offset += 1 << (sb->s_blocksize_bits - i);
    > > 2513 max = max >> 1;
    > > 2514 i++;
    > > 2515 } while (i <= sb->s_blocksize_bits + 1);
    > >
    > > Then, some s_mb_maxs[] becomes 0 due to overflow.
    > > It is cause of this oops. The following patch is to fix it.
    >
    > Looks good to mee; and these lines before it:
    >
    > sbi->s_mb_maxs[0] = sb->s_blocksize << 3;
    > sbi->s_mb_offsets[0] = 0;
    >
    > mean that we would have a problem "even" on 8k blocks, yes?

    Oh, Yes. :-)

    Thanks.

    --
    Yasunori Goto




    \
     
     \ /
      Last update: 2008-12-17 03:49    [W:0.031 / U:0.512 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site