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.c...@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 <mfas...@suse.de>
---
fs/btrfs/compression.c | 6 +++++-
fs/btrfs/extent_io.c | 41 +++++++++++++++++++++++++++++++----------
fs/btrfs/extent_io.h | 3 +++
3 files changed, 39 insertions(+), 11 deletions(-)
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 15b9408..05819c3 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -636,7 +636,11 @@ 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;
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index cdee391..80ce106 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2643,11 +2643,12 @@ static int __extent_read_full_page(struct
extent_io_tree *tree,
struct btrfs_ordered_extent *ordered;
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);
@@ -2659,7 +2660,7 @@ static int __extent_read_full_page(struct extent_io_tree
*tree,
}
end = page_end;
- while (1) {
+ while (!parent_locked) {
lock_extent(tree, start, end);
ordered = btrfs_lookup_ordered_extent(inode, start);
if (!ordered)
@@ -2695,15 +2696,18 @@ static int __extent_read_full_page(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(inode, page, pg_offset, cur,
end - cur + 1, 0);
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;
@@ -2711,7 +2715,7 @@ static int __extent_read_full_page(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);
}
@@ -2755,7 +2759,8 @@ static int __extent_read_full_page(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;
@@ -2765,7 +2770,8 @@ static int __extent_read_full_page(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;
@@ -2783,7 +2789,8 @@ static int __extent_read_full_page(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;
@@ -2811,6 +2818,20 @@ 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 = __extent_read_full_page(tree, page, get_extent, &bio, mirror_num,
+ &bio_flags);
+ 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)
@@ -3666,7 +3687,7 @@ int extent_readpages(struct extent_io_tree *tree,
continue;
for (i = 0; i < nr; i++) {
__extent_read_full_page(tree, pagepool[i], get_extent,
- &bio, 0, &bio_flags);
+ &bio, 0, &bio_flags);
page_cache_release(pagepool[i]);
}
nr = 0;
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 258c921..e3654bd 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -28,6 +28,7 @@
*/
#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 */
@@ -198,6 +199,8 @@ 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);
--
1.8.1.4
--
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