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Commit 4b384318 authored by Mark Fasheh's avatar Mark Fasheh Committed by Chris Mason
Browse files

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: default avatarMark Fasheh <mfasheh@suse.de>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent 32b7c687

fs/btrfs/compression.c

+5 −1
Original line number Diff line number Diff line
@@ -639,6 +639,10 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, 
	faili = nr_pages - 1;

	cb->nr_pages = nr_pages;



	/* 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 */

fs/btrfs/extent_io.c

+29 −8
Original line number Diff line number Diff line
@@ -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);
@@ -2807,7 +2808,9 @@ 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,

			if (!parent_locked)

				unlock_extent_cached(tree, cur,

						     cur + iosize - 1,

						     &cached, GFP_NOFS);

			break;

		}
@@ -2815,6 +2818,7 @@ static int __do_readpage(struct extent_io_tree *tree, 
				      end - cur + 1, get_extent, em_cached);

		if (IS_ERR_OR_NULL(em)) {

			SetPageError(page);

			if (!parent_locked)

				unlock_extent(tree, cur, end);

			break;

		}
@@ -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);

		}
@@ -2867,6 +2871,7 @@ 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);

			if (!parent_locked)

				unlock_extent(tree, cur, cur + iosize - 1);

			cur = cur + iosize;

			pg_offset += iosize;
@@ -2877,6 +2882,7 @@ static int __do_readpage(struct extent_io_tree *tree, 
		 */

		if (block_start == EXTENT_MAP_INLINE) {

			SetPageError(page);

			if (!parent_locked)

				unlock_extent(tree, cur, cur + iosize - 1);

			cur = cur + iosize;

			pg_offset += iosize;
@@ -2895,6 +2901,7 @@ static int __do_readpage(struct extent_io_tree *tree, 
			*bio_flags = this_bio_flag;

		} else {

			SetPageError(page);

			if (!parent_locked)

				unlock_extent(tree, cur, cur + iosize - 1);

		}

		cur = cur + 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)

fs/btrfs/extent_io.h

+3 −0
Original line number Diff line number Diff line
@@ -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);