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nilfs2: refactor nilfs_palloc_find_available_slot()

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The current implementation of nilfs_palloc_find_available_slot() function
is overkill.  The underlying bit search routine is well optimized, so this
uses it more simply in nilfs_palloc_find_available_slot().

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ryusuke Konishi 2015-11-06 16:31:48 -08:00 committed by Linus Torvalds
parent 4e9e63a671
commit 18c41b37f0
1 changed files with 22 additions and 28 deletions
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50
fs/nilfs2/alloc.c
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@ -335,39 +335,33 @@ void *nilfs_palloc_block_get_entry(const struct inode *inode, __u64 nr,
*/
static int nilfs_palloc_find_available_slot(unsigned char *bitmap,
unsigned long target,
int bsize,
unsigned bsize,
spinlock_t *lock)
{
int curr, pos, end, i;
int pos, end = bsize;
if (target > 0) {
end = (target + BITS_PER_LONG - 1) & ~(BITS_PER_LONG - 1);
if (end > bsize)
end = bsize;
pos = nilfs_find_next_zero_bit(bitmap, end, target);
if (pos < end && !nilfs_set_bit_atomic(lock, pos, bitmap))
return pos;
} else {
end = 0;
}
for (i = 0, curr = end;
i < bsize;
i += BITS_PER_LONG, curr += BITS_PER_LONG) {
/* wrap around */
if (curr >= bsize)
curr = 0;
while (*((unsigned long *)bitmap + curr / BITS_PER_LONG)
!= ~0UL) {
end = curr + BITS_PER_LONG;
if (end > bsize)
end = bsize;
pos = nilfs_find_next_zero_bit(bitmap, end, curr);
if (pos < end &&
!nilfs_set_bit_atomic(lock, pos, bitmap))
if (likely(target < bsize)) {
pos = target;
do {
pos = nilfs_find_next_zero_bit(bitmap, end, pos);
if (pos >= end)
break;
if (!nilfs_set_bit_atomic(lock, pos, bitmap))
return pos;
}
} while (++pos < end);
end = target;
}
/* wrap around */
for (pos = 0; pos < end; pos++) {
pos = nilfs_find_next_zero_bit(bitmap, end, pos);
if (pos >= end)
break;
if (!nilfs_set_bit_atomic(lock, pos, bitmap))
return pos;
}
return -ENOSPC;
}