From 207a232ccac0a8cb79d304bd17298dbc96e2e082 Mon Sep 17 00:00:00 2001 From: Arne Jansen Date: Sat, 25 Feb 2012 09:09:47 +0100 Subject: [PATCH] btrfs: don't add both copies of DUP to reada extent tree Normally when there are 2 copies of a block, we add both to the reada extent tree and prefetch only the one that is easier to reach. This way we can better utilize multiple devices. In case of DUP this makes no sense as both copies reside on the same device. Signed-off-by: Arne Jansen --- fs/btrfs/reada.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c index 8dec650099c..ac5d0108588 100644 --- a/fs/btrfs/reada.c +++ b/fs/btrfs/reada.c @@ -326,6 +326,7 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root, struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree; struct btrfs_bio *bbio = NULL; struct btrfs_device *dev; + struct btrfs_device *prev_dev; u32 blocksize; u64 length; int nzones = 0; @@ -405,8 +406,20 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root, spin_unlock(&fs_info->reada_lock); goto error; } + prev_dev = NULL; for (i = 0; i < nzones; ++i) { dev = bbio->stripes[i].dev; + if (dev == prev_dev) { + /* + * in case of DUP, just add the first zone. As both + * are on the same device, there's nothing to gain + * from adding both. + * Also, it wouldn't work, as the tree is per device + * and adding would fail with EEXIST + */ + continue; + } + prev_dev = dev; ret = radix_tree_insert(&dev->reada_extents, index, re); if (ret) { while (--i >= 0) { -- 2.41.0