[PATCH 0/3] d_prune

From: Sage Weil
Date: Wed May 11 2011 - 21:25:07 EST


The Ceph client is told by the server when it has the entire contents of
a directory in cache, and is notified prior to any changes. However,
the current VFS infrastructure does not allow the client to handle a
lookup on a non-existent entry in a non-racy way.

The first patch addes a new d_prune dentry_operation that is called
before the VFS throws dentries out of cache (specifically, before the
victim dentry is unhashed). The next two patches make the necessary
changes in the Ceph fs code to safely clear a D_COMPLETE flag on the
directory dentry when a child is pruned. The third patch specifically
compensates for calls to dentry_unhash() in vfs_rmdir() and
vfs_rename_dir(). The last patch adjusts the Ceph fs code to take
advantage of the new flag. That change is pretty simple because most of
the infrastructure is already in place (we were previously relying on
d_release for notification of pruning in a racy way).

Adding this interface would more or less codify the idea that the VFS
shouldn't unhash random dentries without first calling d_prune. There
are currently two places where the VFS currently unhashes: vfs_rmdir and
vfs_rename_dir both call dentry_unhash(), which is there to make it easy
for simple file systems to avoid races with directory removal and
lookups. That could arguably be pushed down into those file systems,
but it's a more delicate cleanup.



Sage Weil (3):
vfs: add d_prune dentry operation
ceph: clear parent D_COMPLETE flag when on dentry prune
ceph: switch I_COMPLETE to D_COMPLETE

Documentation/filesystems/Locking | 1 +
fs/ceph/caps.c | 8 +--
fs/ceph/dir.c | 87 +++++++++++++++++++++++++++++++++----
fs/ceph/inode.c | 9 ++--
fs/ceph/mds_client.c | 6 +-
fs/ceph/super.h | 23 +++++++++-
fs/dcache.c | 8 +++
include/linux/dcache.h | 3 +
8 files changed, 121 insertions(+), 24 deletions(-)

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