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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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6
fs/btrfs/compression.c
View File

@ -639,7 +639,11 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
faili = nr_pages - 1;
cb->nr_pages = nr_pages;
add_ra_bio_pages(inode, em_start + em_len, cb);
/* In the parent-locked case, we only locked the range we are
* interested in. In all other cases, we can opportunistically
* cache decompressed data that goes beyond the requested range. */
if (!(bio_flags & EXTENT_BIO_PARENT_LOCKED))
add_ra_bio_pages(inode, em_start + em_len, cb);
/* include any pages we added in add_ra-bio_pages */
uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;

37
fs/btrfs/extent_io.c
View File

@ -2764,11 +2764,12 @@ static int __do_readpage(struct extent_io_tree *tree,
struct block_device *bdev;
int ret;
int nr = 0;
int parent_locked = *bio_flags & EXTENT_BIO_PARENT_LOCKED;
size_t pg_offset = 0;
size_t iosize;
size_t disk_io_size;
size_t blocksize = inode->i_sb->s_blocksize;
unsigned long this_bio_flag = 0;
unsigned long this_bio_flag = *bio_flags & EXTENT_BIO_PARENT_LOCKED;
set_page_extent_mapped(page);
@ -2807,15 +2808,18 @@ static int __do_readpage(struct extent_io_tree *tree,
kunmap_atomic(userpage);
set_extent_uptodate(tree, cur, cur + iosize - 1,
&cached, GFP_NOFS);
unlock_extent_cached(tree, cur, cur + iosize - 1,
&cached, GFP_NOFS);
if (!parent_locked)
unlock_extent_cached(tree, cur,
cur + iosize - 1,
&cached, GFP_NOFS);
break;
}
em = __get_extent_map(inode, page, pg_offset, cur,
end - cur + 1, get_extent, em_cached);
if (IS_ERR_OR_NULL(em)) {
SetPageError(page);
unlock_extent(tree, cur, end);
if (!parent_locked)
unlock_extent(tree, cur, end);
break;
}
extent_offset = cur - em->start;
@ -2823,7 +2827,7 @@ static int __do_readpage(struct extent_io_tree *tree,
BUG_ON(end < cur);
if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
this_bio_flag = EXTENT_BIO_COMPRESSED;
this_bio_flag |= EXTENT_BIO_COMPRESSED;
extent_set_compress_type(&this_bio_flag,
em->compress_type);
}
@ -2867,7 +2871,8 @@ static int __do_readpage(struct extent_io_tree *tree,
if (test_range_bit(tree, cur, cur_end,
EXTENT_UPTODATE, 1, NULL)) {
check_page_uptodate(tree, page);
unlock_extent(tree, cur, cur + iosize - 1);
if (!parent_locked)
unlock_extent(tree, cur, cur + iosize - 1);
cur = cur + iosize;
pg_offset += iosize;
continue;
@ -2877,7 +2882,8 @@ static int __do_readpage(struct extent_io_tree *tree,
*/
if (block_start == EXTENT_MAP_INLINE) {
SetPageError(page);
unlock_extent(tree, cur, cur + iosize - 1);
if (!parent_locked)
unlock_extent(tree, cur, cur + iosize - 1);
cur = cur + iosize;
pg_offset += iosize;
continue;
@ -2895,7 +2901,8 @@ static int __do_readpage(struct extent_io_tree *tree,
*bio_flags = this_bio_flag;
} else {
SetPageError(page);
unlock_extent(tree, cur, cur + iosize - 1);
if (!parent_locked)
unlock_extent(tree, cur, cur + iosize - 1);
}
cur = cur + iosize;
pg_offset += iosize;
@ -3021,6 +3028,20 @@ int extent_read_full_page(struct extent_io_tree *tree, struct page *page,
return ret;
}
int extent_read_full_page_nolock(struct extent_io_tree *tree, struct page *page,
get_extent_t *get_extent, int mirror_num)
{
struct bio *bio = NULL;
unsigned long bio_flags = EXTENT_BIO_PARENT_LOCKED;
int ret;
ret = __do_readpage(tree, page, get_extent, NULL, &bio, mirror_num,
&bio_flags, READ);
if (bio)
ret = submit_one_bio(READ, bio, mirror_num, bio_flags);
return ret;
}
static noinline void update_nr_written(struct page *page,
struct writeback_control *wbc,
unsigned long nr_written)

3
fs/btrfs/extent_io.h
View File

@ -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);