On Mon, Jan 30, 2017 at 05:02:45PM -0800, Omar Sandoval wrote:
> On Sat, Jan 28, 2017 at 06:06:32AM +0000, fdmanana@xxxxxxxxxx wrote:
> > From: Filipe Manana <fdmanana@xxxxxxxx>
> >
> > Very often we have the checksums for an extent spread in multiple items
> > in the checksums tree, and currently the algorithm to delete them starts
> > by looking for them one by one and then deleting them one by one, which
> > is not optimal since each deletion involves shifting all the other items
> > in the leaf and when the leaf reaches some low threshold, to move items
> > off the leaf into its left and right neighbor leafs. Also, after each
> > item deletion we release our search path and start a new search for other
> > checksums items.
> >
> > So optimize this by deleting in bulk all the items in the same leaf that
> > contain checksums for the extent being freed.
> >
> > Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
> > ---
> > fs/btrfs/file-item.c | 28 +++++++++++++++++++++++++++-
> > 1 file changed, 27 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> > index e97e322..d7d6d4a 100644
> > --- a/fs/btrfs/file-item.c
> > +++ b/fs/btrfs/file-item.c
> > @@ -643,7 +643,33 @@ int btrfs_del_csums(struct btrfs_trans_handle *trans,
> >
> > /* delete the entire item, it is inside our range */
> > if (key.offset >= bytenr && csum_end <= end_byte) {
> > - ret = btrfs_del_item(trans, root, path);
> > + int del_nr = 1;
> > +
> > + /*
> > + * Check how many csum items preceding this one in this
> > + * leaf correspond to our range and then delete them all
> > + * at once.
> > + */
> > + if (key.offset > bytenr && path->slots[0] > 0) {
> > + int slot = path->slots[0] - 1;
> > +
> > + while (slot >= 0) {
> > + struct btrfs_key pk;
> > +
> > + btrfs_item_key_to_cpu(leaf, &pk, slot);
> > + if (pk.offset < bytenr ||
> > + pk.type != BTRFS_EXTENT_CSUM_KEY ||
> > + pk.objectid !=
> > + BTRFS_EXTENT_CSUM_OBJECTID)
> > + break;
> > + path->slots[0] = slot;
> > + del_nr++;
> > + key.offset = pk.offset;
> > + slot--;
> > + }
> > + }
> > + ret = btrfs_del_items(trans, root, path,
> > + path->slots[0], del_nr);
> > if (ret)
> > goto out;
> > if (key.offset == bytenr)
>
> Hmm, this seems like the kind of operation that could use a helper.
> btrfs_del_item_range() or something like that, which takes the maximum
> key to delete. What do you think?
Err, or in this case, the minimum key.
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