Commit cb689481 authored by Filipe Manana's avatar Filipe Manana Committed by David Sterba
Browse files

btrfs: send: avoid unnecessary generation search at did_overwrite_ref() 



At did_overwrite_ref() we always call get_inode_gen() to find out the
generation of the inode 'ow_inode'. However we don't always need to use
that generation, and in fact it's very common to not use it, so we end
up doing a b+tree search on the send root, allocating a path, etc, for
nothing. So improve on this by getting the generation only if we need
to use it.

This patch is part of a larger patchset and the changelog of the last
patch in the series contains a sample performance test and results.
The patches that comprise the patchset are the following:

  btrfs: send: directly return from did_overwrite_ref() and simplify it
  btrfs: send: avoid unnecessary generation search at did_overwrite_ref()
  btrfs: send: directly return from will_overwrite_ref() and simplify it
  btrfs: send: avoid extra b+tree searches when checking reference overrides
  btrfs: send: remove send_progress argument from can_rmdir()
  btrfs: send: avoid duplicated orphan dir allocation and initialization
  btrfs: send: avoid unnecessary orphan dir rbtree search at can_rmdir()
  btrfs: send: reduce searches on parent root when checking if dir can be removed
  btrfs: send: iterate waiting dir move rbtree only once when processing refs
  btrfs: send: initialize all the red black trees earlier
  btrfs: send: genericize the backref cache to allow it to be reused
  btrfs: adapt lru cache to allow for 64 bits keys on 32 bits systems
  btrfs: send: cache information about created directories
  btrfs: allow a generation number to be associated with lru cache entries
  btrfs: add an api to delete a specific entry from the lru cache
  btrfs: send: use the lru cache to implement the name cache
  btrfs: send: update size of roots array for backref cache entries
  btrfs: send: cache utimes operations for directories if possible

Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent e739ba30

fs/btrfs/send.c

+22 −9
Original line number Diff line number Diff line
@@ -2193,8 +2193,8 @@ static int did_overwrite_ref(struct send_ctx *sctx, 
			    const char *name, int name_len)

{

	int ret;

	u64 gen;

	u64 ow_inode;

	u64 ow_gen = 0;



	if (!sctx->parent_root)

		return 0;
@@ -2204,6 +2204,8 @@ static int did_overwrite_ref(struct send_ctx *sctx, 
		return ret;



	if (dir != BTRFS_FIRST_FREE_OBJECTID) {

		u64 gen;



		ret = get_inode_gen(sctx->send_root, dir, &gen);

		if (ret == -ENOENT)

			return 0;
@@ -2224,12 +2226,15 @@ static int did_overwrite_ref(struct send_ctx *sctx, 
		return ret;

	}



	ret = get_inode_gen(sctx->send_root, ow_inode, &gen);

	if (ow_inode == ino) {

		ret = get_inode_gen(sctx->send_root, ow_inode, &ow_gen);

		if (ret < 0)

			return ret;



	if (ow_inode == ino && gen == ino_gen)

		/* It's the same inode, so no overwrite happened. */

		if (ow_gen == ino_gen)

			return 0;

	}



	/*

	 * We know that it is or will be overwritten. Check this now.
@@ -2237,10 +2242,18 @@ static int did_overwrite_ref(struct send_ctx *sctx, 
	 * inode 'ino' to be orphanized, therefore check if ow_inode matches

	 * the current inode being processed.

	 */

	if ((ow_inode < sctx->send_progress) ||

	    (ino != sctx->cur_ino && ow_inode == sctx->cur_ino &&

	     gen == sctx->cur_inode_gen))

	if (ow_inode < sctx->send_progress)

		return 1;



	if (ino != sctx->cur_ino && ow_inode == sctx->cur_ino) {

		if (ow_gen == 0) {

			ret = get_inode_gen(sctx->send_root, ow_inode, &ow_gen);

			if (ret < 0)

				return ret;

		}

		if (ow_gen == sctx->cur_inode_gen)

			return 1;

	}



	return 0;

}