Btrfs: reduce CPU usage in the extent_state tree

Btrfs is currently mirroring some of the page state bits into
its extent state tree.  The goal behind this was to use it in supporting
blocksizes other than the page size.

But, we don't currently support that, and we're using quite a lot of CPU
on the rb tree and its spin lock.  This commit starts a series of
cleanups to reduce the amount of work done in the extent state tree as
part of each IO.

This commit:

* Adds the ability to lock an extent in the state tree and also set
other bits.  The idea is to do locking and delalloc in one call

* Removes the EXTENT_WRITEBACK and EXTENT_DIRTY bits.  Btrfs is using
a combination of the page bits and the ordered write code for this
instead.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 0 insertions, 19 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 8a9c76aecdf3..ef66c3d989b9 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -113,8 +113,6 @@ static noinline int dirty_and_release_pages(struct btrfs_trans_handle *trans,
         int err = 0;
         int i;
         struct inode *inode = fdentry(file)->d_inode;
-        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
-        u64 hint_byte;
         u64 num_bytes;
         u64 start_pos;
         u64 end_of_last_block;
@@ -126,20 +124,6 @@ static noinline int dirty_and_release_pages(struct btrfs_trans_handle *trans,
                     root->sectorsize - 1) & ~((u64)root->sectorsize - 1);
 
         end_of_last_block = start_pos + num_bytes - 1;
-
-        lock_extent(io_tree, start_pos, end_of_last_block, GFP_NOFS);
-        trans = btrfs_join_transaction(root, 1);
-        if (!trans) {
-                err = -ENOMEM;
-                goto out_unlock;
-        }
-        btrfs_set_trans_block_group(trans, inode);
-        hint_byte = 0;
-
-        /* check for reserved extents on each page, we don't want
-         * to reset the delalloc bit on things that already have
-         * extents reserved.
-         */
         btrfs_set_extent_delalloc(inode, start_pos, end_of_last_block);
         for (i = 0; i < num_pages; i++) {
                 struct page *p = pages[i];
@@ -154,9 +138,6 @@ static noinline int dirty_and_release_pages(struct btrfs_trans_handle *trans,
                  * at this time.
                  */
         }
-        err = btrfs_end_transaction(trans, root);
-out_unlock:
-        unlock_extent(io_tree, start_pos, end_of_last_block, GFP_NOFS);
         return err;
 }