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btrfs: update num_extent_pages to support subpage sized extent buffer 

For subpage sized extent buffer, we have ensured no extent buffer will
cross page boundary, thus we would only need one page for any extent
buffer.

Update function num_extent_pages to handle such case.  Now
num_extent_pages() returns 1 for subpage sized extent buffer.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2020-12-02 14:48:03 +08:00 committed by David Sterba
parent 1aaac38c83
commit 4a3dc93843
1 changed files with 8 additions and 2 deletions
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10
fs/btrfs/extent_io.h
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@ -203,8 +203,14 @@ void btrfs_readahead_node_child(struct extent_buffer *node, int slot);
static inline int num_extent_pages(const struct extent_buffer *eb)
{
return (round_up(eb->start + eb->len, PAGE_SIZE) >> PAGE_SHIFT) -
(eb->start >> PAGE_SHIFT);
/*
* For sectorsize == PAGE_SIZE case, since nodesize is always aligned to
* sectorsize, it's just eb->len >> PAGE_SHIFT.
*
* For sectorsize < PAGE_SIZE case, we could have nodesize < PAGE_SIZE,
* thus have to ensure we get at least one page.
*/
return (eb->len >> PAGE_SHIFT) ?: 1;
}
static inline int extent_buffer_uptodate(const struct extent_buffer *eb)