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: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 23442747363ed920cf395af4c233f739888e3c3c..90310d9e647a802f647b9e2267848299dbe17403 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -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) {

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 970190cd347edd5878479618222dc814b4736573..0dfcef37352b0127d25fbe561acafe7f139be950 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -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,

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index faffa28ba707f3733e841aff16b02da259730249..861dacb371c7f92759fc816feffeb01864f02778 100644 (file)
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -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 */