lkml.org 
[lkml]   [2008]   [Dec]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[Patch/BUG] (ext4) s_mb_maxs[] of ext4_sb_info is too small size
    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.

    Thanks.

    ----

    The size of s_mb_maxs that is defined in ext4_sb_info is too small.
    When block size is 64K, which is possible on ia64,
    the maximum value of s_mb_maxs becomes 256K(0x40000).
    However, s_mb_maxs is defined as unsigned short. This is cause of panic.

    Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
    Cc: Li Zefan <lizf@cn.fujitsu.com>
    Cc: Miao Xie <miaox@cn.fujitsu.com>

    ---
    fs/ext4/ext4_sb.h | 3 ++-
    fs/ext4/mballoc.c | 2 ++
    2 files changed, 4 insertions(+), 1 deletion(-)

    Index: test2/fs/ext4/ext4_sb.h
    ===================================================================
    --- test2.orig/fs/ext4/ext4_sb.h 2008-12-16 11:20:18.000000000 +0900
    +++ test2/fs/ext4/ext4_sb.h 2008-12-16 14:17:32.000000000 +0900
    @@ -101,7 +101,8 @@ struct ext4_sb_info {
    spinlock_t s_reserve_lock;
    spinlock_t s_md_lock;
    tid_t s_last_transaction;
    - unsigned short *s_mb_offsets, *s_mb_maxs;
    + unsigned short *s_mb_offsets;
    + unsigned int *s_mb_maxs;

    /* tunables */
    unsigned long s_stripe;
    Index: test2/fs/ext4/mballoc.c
    ===================================================================
    --- test2.orig/fs/ext4/mballoc.c 2008-12-16 11:20:18.000000000 +0900
    +++ test2/fs/ext4/mballoc.c 2008-12-16 14:23:21.000000000 +0900
    @@ -2493,6 +2493,8 @@ int ext4_mb_init(struct super_block *sb,
    if (sbi->s_mb_offsets == NULL) {
    return -ENOMEM;
    }
    +
    + i = (sb->s_blocksize_bits + 2) * sizeof(unsigned int);
    sbi->s_mb_maxs = kmalloc(i, GFP_KERNEL);
    if (sbi->s_mb_maxs == NULL) {
    kfree(sbi->s_mb_maxs);
    --
    Yasunori Goto




    \
     
     \ /
      Last update: 2008-12-16 09:29    [W:0.025 / U:62.684 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site