ext4: Fix mb_find_next_bit not to return larger than max From: "Aneesh Kumar K.V" Some architectures implement ext4_find_next_bit and ext4_find_next_zero_bit in such a way that they return greater than max for some input values. Make sure mb_find_next_bit and mb_find_next_zero_bit return the right values. On 2.6.25 we have include/asm-x86/bitops_32.h static inline unsigned find_first_bit(const unsigned long *addr, unsigned size) { unsigned x = 0; while (x < size) { unsigned long val = *addr++; if (val) return __ffs(val) + x; x += (sizeof(*addr)<<3); } return x; } This can return value greater than size. Reported and fixed here for lustre https://bugzilla.lustre.org/show_bug.cgi?id=15932 https://bugzilla.lustre.org/attachment.cgi?id=17205 Signed-off-by: Aneesh Kumar K.V Signed-off-by: Mingming Cao Signed-off-by: "Theodore Ts'o" --- fs/ext4/mballoc.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) Index: linux-2.6.26-rc9/fs/ext4/mballoc.c =================================================================== --- linux-2.6.26-rc9.orig/fs/ext4/mballoc.c 2008-07-11 16:04:32.000000000 -0700 +++ linux-2.6.26-rc9/fs/ext4/mballoc.c 2008-07-11 16:04:56.000000000 -0700 @@ -381,22 +381,28 @@ static inline void mb_clear_bit_atomic(s static inline int mb_find_next_zero_bit(void *addr, int max, int start) { - int fix = 0; + int fix = 0, ret, tmpmax; addr = mb_correct_addr_and_bit(&fix, addr); - max += fix; + tmpmax = max + fix; start += fix; - return ext4_find_next_zero_bit(addr, max, start) - fix; + ret = ext4_find_next_zero_bit(addr, tmpmax, start) - fix; + if (ret > max) + return max; + return ret; } static inline int mb_find_next_bit(void *addr, int max, int start) { - int fix = 0; + int fix = 0, ret, tmpmax; addr = mb_correct_addr_and_bit(&fix, addr); - max += fix; + tmpmax = max + fix; start += fix; - return ext4_find_next_bit(addr, max, start) - fix; + ret = ext4_find_next_bit(addr, tmpmax, start) - fix; + if (ret > max) + return max; + return ret; } static void *mb_find_buddy(struct ext4_buddy *e4b, int order, int *max) @@ -3473,8 +3479,6 @@ ext4_mb_release_inode_pa(struct ext4_bud if (bit >= end) break; next = mb_find_next_bit(bitmap_bh->b_data, end, bit); - if (next > end) - next = end; start = group * EXT4_BLOCKS_PER_GROUP(sb) + bit + le32_to_cpu(sbi->s_es->s_first_data_block); mb_debug(" free preallocated %u/%u in group %u\n",