features/shard: optimization over shard lookup in case of prealloc

Assume that we are preallocating a VM of size 1TB with a shard
block size of 64MB then there will be ~16k shards.

This creation happens in 2 steps shard_fallocate() path i.e

1. lookup for the shards if any already present and
2. mknod over those shards do not exist.

But in case of fresh creation, we dont have to lookup for all
shards which are not present as the the file size will be 0.
Through this, we can save lookup on all shards which are not
present. This optimization is quite useful in the case of
preallocating big vm.

Also if the file is already present and the call is to
extend it to bigger size then we need not to lookup for non-
existent shards. Just lookup preexisting shards, populate
the inodes and issue mknod on extended size.

Fixes: #1425
Change-Id: I60036fe8302c696e0ca80ff11ab0ef5bcdbd7880
Signed-off-by: Vinayakswami Hariharmath <vharihar@redhat.com>

0 files changed, 0 insertions, 0 deletions