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btrfs: Implement find_first_clear_extent_bit 

This function is very similar to find_first_extent_bit except that it
locates the first contiguous span of space which does not have bits set.
It's intended use is in the freespace trimming code.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Nikolay Borisov 2019-03-27 14:24:17 +02:00 committed by David Sterba
parent 8811133d8a
commit 45bfcfc168
2 changed files with 75 additions and 0 deletions
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73
fs/btrfs/extent_io.c
View File

@ -1542,6 +1542,79 @@ out:
return ret;
}
/**
* find_first_clear_extent_bit - finds the first range that has @bits not set
* and that starts after @start
*
* @tree - the tree to search
* @start - the offset at/after which the found extent should start
* @start_ret - records the beginning of the range
* @end_ret - records the end of the range (inclusive)
* @bits - the set of bits which must be unset
*
* Since unallocated range is also considered one which doesn't have the bits
* set it's possible that @end_ret contains -1, this happens in case the range
* spans (last_range_end, end of device]. In this case it's up to the caller to
* trim @end_ret to the appropriate size.
*/
void find_first_clear_extent_bit(struct extent_io_tree *tree, u64 start,
u64 *start_ret, u64 *end_ret, unsigned bits)
{
struct extent_state *state;
struct rb_node *node, *prev = NULL, *next;
spin_lock(&tree->lock);
/* Find first extent with bits cleared */
while (1) {
node = __etree_search(tree, start, &next, &prev, NULL, NULL);
if (!node) {
node = next;
if (!node) {
/*
* We are past the last allocated chunk,
* set start at the end of the last extent. The
* device alloc tree should never be empty so
* prev is always set.
*/
ASSERT(prev);
state = rb_entry(prev, struct extent_state, rb_node);
*start_ret = state->end + 1;
*end_ret = -1;
goto out;
}
}
state = rb_entry(node, struct extent_state, rb_node);
if (in_range(start, state->start, state->end - state->start + 1) &&
(state->state & bits)) {
start = state->end + 1;
} else {
*start_ret = start;
break;
}
}
/*
* Find the longest stretch from start until an entry which has the
* bits set
*/
while (1) {
state = rb_entry(node, struct extent_state, rb_node);
if (state->end >= start && !(state->state & bits)) {
*end_ret = state->end;
} else {
*end_ret = state->start - 1;
break;
}
node = rb_next(node);
if (!node)
break;
}
out:
spin_unlock(&tree->lock);
}
/*
* find a contiguous range of bytes in the file marked as delalloc, not
* more than 'max_bytes'. start and end are used to return the range,

2
fs/btrfs/extent_io.h
View File

@ -403,6 +403,8 @@ static inline int set_extent_uptodate(struct extent_io_tree *tree, u64 start,
int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
u64 *start_ret, u64 *end_ret, unsigned bits,
struct extent_state **cached_state);
void find_first_clear_extent_bit(struct extent_io_tree *tree, u64 start,
u64 *start_ret, u64 *end_ret, unsigned bits);
int extent_invalidatepage(struct extent_io_tree *tree,
struct page *page, unsigned long offset);
int extent_write_full_page(struct page *page, struct writeback_control *wbc);