btrfs: Introduce extent_read_full_page_nolock()
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>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index a8d662b..df6e6c2 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2764,11 +2764,12 @@
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 @@
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 @@
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 @@
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 @@
*/
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 @@
*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 @@
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)