btrfs: move page locking from lock_extent_buffer_for_io to write_one_eb

Locking the pages in lock_extent_buffer_for_io only for the non-subpage
case is very confusing.  Move it to write_one_eb to mirror the subpage
case and simplify the code. Now lock_extent_buffer_for_io does not leave
all the pages locked and each is individually locked/unlocked in
write_one_eb.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 40b612c..6284dfd 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1636,7 +1636,6 @@ static noinline_for_stack bool lock_extent_buffer_for_io(struct extent_buffer *e
 {
        struct btrfs_fs_info *fs_info = eb->fs_info;
        bool ret = false;
-       int i;
 
        btrfs_tree_lock(eb);
        while (test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags)) {
@@ -1664,20 +1663,7 @@ static noinline_for_stack bool lock_extent_buffer_for_io(struct extent_buffer *e
        } else {
                spin_unlock(&eb->refs_lock);
        }
-
        btrfs_tree_unlock(eb);
-
-       /*
-        * Either we don't need to submit any tree block, or we're submitting
-        * subpage eb.
-        * Subpage metadata doesn't use page locking at all, so we can skip
-        * the page locking.
-        */
-       if (!ret || fs_info->nodesize < PAGE_SIZE)
-               return ret;
-
-       for (i = 0; i < num_extent_pages(eb); i++)
-               lock_page(eb->pages[i]);
        return ret;
 }
 
@@ -1960,6 +1946,7 @@ static noinline_for_stack void write_one_eb(struct extent_buffer *eb,
        for (i = 0; i < num_pages; i++) {
                struct page *p = eb->pages[i];
 
+               lock_page(p);
                clear_page_dirty_for_io(p);
                set_page_writeback(p);
                submit_extent_page(&bio_ctrl, disk_bytenr, p, PAGE_SIZE, 0);