tree aaf42da2b6086a58d84efd4ef39a312f03cfbefb
parent 35e478f42271673f79066a1ed008c6604621c6fe
author Steven Whitehouse <swhiteho@redhat.com> 1331208623 +0000
committer Steven Whitehouse <swhiteho@redhat.com> 1331208623 +0000

GFS2: Remove a __GFP_NOFAIL allocation

In order to ensure that we've got enough buffer heads for flushing
the journal, the orignal code used __GFP_NOFAIL when performing
this allocation. Here we dispense with that in favour of using a
mempool. This should improve efficiency in low memory conditions
since flushing the journal is a good way to get memory back, we
don't want to be spinning, waiting on memory allocations. The
buffers which are allocated via this mempool are fairly short lived,
so that we'll recycle them pretty quickly.

Although there are other memory allocations which occur during the
journal flush process, this is the one which can potentially require
the most memory, so the most important one to fix.

The amount of memory reserved is a fixed amount, and we should not need
to scale it when there are a greater number of filesystems in use.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>