http://kerneloops.org/raw.php?rawid=176715 and http://bugzilla.kernel.org/show_bug.cgi?id=12433 report a bug when resizing a mounted ext4 filesystem. I could easily reproduce it using 2.6.29-rc2, 2.6.28 and 2.6.27. ext4_error was called just before the NULL derefence from ext4_get_group_desc, indicating a block group beyond s_groups_count. This function returned a NULL. The requested block group was beyond s_groups_count because this is the last changed bit when resizing. The caller, ext4_group_used_meta_blocks, did not check the returned pointer. It needs the gdp anyway. Fortunately, its only caller, ext4_init_block_bitmap, has a gdp and it was simply a matter of adding this parameter to ext4_group_used_meta_blocks and use it. Tested and the oops is gone. Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxxx> --- fs/ext4/balloc.c | 8 ++------ 1 files changed, 2 insertions(+), 6 deletions(-) diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 9a50b80..d7dc22a 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -55,7 +55,7 @@ static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block, } static int ext4_group_used_meta_blocks(struct super_block *sb, - ext4_group_t block_group) + ext4_group_t block_group, struct ext4_group_desc *gdp) { ext4_fsblk_t tmp; struct ext4_sb_info *sbi = EXT4_SB(sb); @@ -63,10 +63,6 @@ static int ext4_group_used_meta_blocks(struct super_block *sb, int used_blocks = sbi->s_itb_per_group + 2; if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) { - struct ext4_group_desc *gdp; - struct buffer_head *bh; - - gdp = ext4_get_group_desc(sb, block_group, &bh); if (!ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) used_blocks--; @@ -177,7 +173,7 @@ unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh, */ mark_bitmap_end(group_blocks, sb->s_blocksize * 8, bh->b_data); } - return free_blocks - ext4_group_used_meta_blocks(sb, block_group); + return free_blocks - ext4_group_used_meta_blocks(sb, block_group, gdp); } -- 1.6.0.6 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
