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btrfs: Introduce extent_read_full_page_nolock()

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We want this for btrfs_extent_same. Basically readpage and friends do their
own extent locking but for the purposes of dedupe, we want to have both
files locked down across a set of readpage operations (so that we can
compare data). Introduce this variant and a flag which can be set for
extent_read_full_page() to indicate that we are already locked.

Partial credit for this patch goes to Gabriel de Perthuis <g2p.code@gmail.com>
as I have included a fix from him to the original patch which avoids a
deadlock on compressed extents.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
This commit is contained in:
Mark Fasheh
2013-08-06 11:42:50 -07:00
committed by Chris Mason
parent 32b7c687c5
commit 4b384318a7
3 changed files with 37 additions and 9 deletions
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3
fs/btrfs/extent_io.h
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@@ -29,6 +29,7 @@
*/
#define EXTENT_BIO_COMPRESSED 1
#define EXTENT_BIO_TREE_LOG 2
#define EXTENT_BIO_PARENT_LOCKED 4
#define EXTENT_BIO_FLAG_SHIFT 16
/* these are bit numbers for test/set bit */
@@ -199,6 +200,8 @@ int unlock_extent_cached(struct extent_io_tree *tree, u64 start, u64 end,
int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end);
int extent_read_full_page(struct extent_io_tree *tree, struct page *page,
get_extent_t *get_extent, int mirror_num);
int extent_read_full_page_nolock(struct extent_io_tree *tree, struct page *page,
get_extent_t *get_extent, int mirror_num);
int __init extent_io_init(void);
void extent_io_exit(void);