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Commit 18fdc679 authored by Liu Bo's avatar Liu Bo Committed by David Sterba
Browse files

Btrfs: remove bio_flags which indicates a meta block of log-tree 



Since both committing transaction and writing log-tree are doing
plugging on metadata IO, we can unify to use %sync_writers to benefit
both cases, instead of checking bio_flags while writing meta blocks of
log-tree.

We can remove this bio_flags because in order to write dirty blocks,
log tree also uses btrfs_write_marked_extents(), inside which we
have enabled %sync_writers, therefore, every write goes in a
synchronous way, so does checksuming.

Please also note that, bio_flags is applied per-context while
%sync_writers is applied per-inode, so this might incur some overhead, ie.

1) while log tree is flushing its dirty blocks via
   btrfs_write_marked_extents(), in which %sync_writers is increased
   by one.

2) in the meantime, some writeback operations may happen upon btrfs's
   metadata inode, so these writes go synchronously, too.

However, AFAICS, the overhead is not a big one while the win is that
we unify the two places that needs synchronous way and remove a
special hack/flag.

This removes the bio_flags related stuff for writing log-tree.

Signed-off-by: default avatarLiu Bo <bo.li.liu@oracle.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 6300463b

fs/btrfs/disk-io.c

+2 −4
Original line number Diff line number Diff line
@@ -1005,12 +1005,10 @@ static blk_status_t __btree_submit_bio_done(void *private_data, struct bio *bio, 
	return ret;

}



static int check_async_write(struct btrfs_inode *bi, unsigned long bio_flags)

static int check_async_write(struct btrfs_inode *bi)

{

	if (atomic_read(&bi->sync_writers))

		return 0;

	if (bio_flags & EXTENT_BIO_TREE_LOG)

		return 0;

#ifdef CONFIG_X86

	if (static_cpu_has(X86_FEATURE_XMM4_2))

		return 0;
@@ -1024,7 +1022,7 @@ static blk_status_t btree_submit_bio_hook(void *private_data, struct bio *bio, 
{

	struct inode *inode = private_data;

	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

	int async = check_async_write(BTRFS_I(inode), bio_flags);

	int async = check_async_write(BTRFS_I(inode));

	blk_status_t ret;



	if (bio_op(bio) != REQ_OP_WRITE) {

fs/btrfs/extent_io.c

+2 −11
Original line number Diff line number Diff line
@@ -109,7 +109,6 @@ struct extent_page_data { 
	struct bio *bio;

	struct extent_io_tree *tree;

	get_extent_t *get_extent;

	unsigned long bio_flags;



	/* tells writepage not to lock the state bits for this range

	 * it still does the unlocking
@@ -3715,7 +3714,6 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb, 
	u64 offset = eb->start;

	u32 nritems;

	unsigned long i, num_pages;

	unsigned long bio_flags = 0;

	unsigned long start, end;

	unsigned int write_flags = wbc_to_write_flags(wbc) | REQ_META;

	int ret = 0;
@@ -3723,8 +3721,6 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb, 
	clear_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags);

	num_pages = num_extent_pages(eb->start, eb->len);

	atomic_set(&eb->io_pages, num_pages);

	if (btrfs_header_owner(eb) == BTRFS_TREE_LOG_OBJECTID)

		bio_flags = EXTENT_BIO_TREE_LOG;



	/* set btree blocks beyond nritems with 0 to avoid stale content. */

	nritems = btrfs_header_nritems(eb);
@@ -3751,8 +3747,7 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb, 
					 p, offset >> 9, PAGE_SIZE, 0, bdev,

					 &epd->bio,

					 end_bio_extent_buffer_writepage,

					 0, epd->bio_flags, bio_flags, false);

		epd->bio_flags = bio_flags;

					 0, 0, 0, false);

		if (ret) {

			set_btree_ioerr(p);

			if (PageWriteback(p))
@@ -3789,7 +3784,6 @@ int btree_write_cache_pages(struct address_space *mapping, 
		.tree = tree,

		.extent_locked = 0,

		.sync_io = wbc->sync_mode == WB_SYNC_ALL,

		.bio_flags = 0,

	};

	int ret = 0;

	int done = 0;
@@ -4062,7 +4056,7 @@ static void flush_epd_write_bio(struct extent_page_data *epd) 
	if (epd->bio) {

		int ret;



		ret = submit_one_bio(epd->bio, 0, epd->bio_flags);

		ret = submit_one_bio(epd->bio, 0, 0);

		BUG_ON(ret < 0); /* -ENOMEM */

		epd->bio = NULL;

	}
@@ -4085,7 +4079,6 @@ int extent_write_full_page(struct extent_io_tree *tree, struct page *page, 
		.get_extent = get_extent,

		.extent_locked = 0,

		.sync_io = wbc->sync_mode == WB_SYNC_ALL,

		.bio_flags = 0,

	};



	ret = __extent_writepage(page, wbc, &epd);
@@ -4110,7 +4103,6 @@ int extent_write_locked_range(struct extent_io_tree *tree, struct inode *inode, 
		.get_extent = get_extent,

		.extent_locked = 1,

		.sync_io = mode == WB_SYNC_ALL,

		.bio_flags = 0,

	};

	struct writeback_control wbc_writepages = {

		.sync_mode	= mode,
@@ -4150,7 +4142,6 @@ int extent_writepages(struct extent_io_tree *tree, 
		.get_extent = get_extent,

		.extent_locked = 0,

		.sync_io = wbc->sync_mode == WB_SYNC_ALL,

		.bio_flags = 0,

	};



	ret = extent_write_cache_pages(mapping, wbc, __extent_writepage, &epd,

fs/btrfs/extent_io.h

+0 −1
Original line number Diff line number Diff line
@@ -33,7 +33,6 @@ 
 * type for this bio

 */

#define EXTENT_BIO_COMPRESSED 1

#define EXTENT_BIO_TREE_LOG 2

#define EXTENT_BIO_FLAG_SHIFT 16



/* these are bit numbers for test/set bit */