tree c9a637653e547f24ed488d0d5956b314b4257597
parent 062c05c46bd4358aad7a0e0cb5ffeb98ab935286
author Alexandre Oliva <oliva@lsd.ic.unicamp.br> 1323306520 -0500
committer Chris Mason <chris.mason@oracle.com> 1323352540 -0500

Btrfs: try cluster but don't advance in search list

When we find an existing cluster, we switch to its block group as the
current block group, possibly skipping multiple blocks in the process.
Furthermore, under heavy contention, multiple threads may fail to
allocate from a cluster and then release just-created clusters just to
proceed to create new ones in a different block group.

This patch tries to allocate from an existing cluster regardless of its
block group, and doesn't switch to that group, instead proceeding to
try to allocate a cluster from the group it was iterating before the
attempt.

Signed-off-by: Alexandre Oliva <oliva@lsd.ic.unicamp.br>
Signed-off-by: Chris Mason <chris.mason@oracle.com>