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Commit e7dfb246 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Theodore Ts'o
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ext4: Fix mb_find_next_bit not to return larger than max 

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: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarMingming Cao <cmm@us.ibm.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent f3b35f06

fs/ext4/mballoc.c

+12 −8
Original line number Diff line number Diff line
@@ -381,22 +381,28 @@ static inline void mb_clear_bit_atomic(spinlock_t *lock, int bit, void *addr) 


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_buddy *e4b, struct buffer_head *bitmap_bh, 
		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",