[PATCH 014/102] xfs: optimize fsync on directories

Dave Chinner
2012-08-23T05:02:50Z

From: Christoph Hellwig <hch@infradead.org>

Upstream commit: 1da2f2dbf2d2aaa1b0f6ca2f61fcf07e24eb659b

Directories are only updated transactionally, which means fsync only
needs to flush the log the inode is currently dirty, but not bother
with checking for dirty data, non-transactional updates, and most
importanly doesn't have to flush disk caches except as part of a
transaction commit.

While the first two optimizations can't easily be measured, the
latter actually makes a difference when doing lots of fsync that do
not actually have to commit the inode, e.g. because an earlier fsync
already pushed the log far enough.

The new xfs_dir_fsync is identical to xfs_nfs_commit_metadata except
for the prototype, but I'm not sure creating a common helper for the
two is worth it given how simple the functions are.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
---
fs/xfs/linux-2.6/xfs_file.c | 29 ++++++++++++++++++++++++++++-
fs/xfs/linux-2.6/xfs_trace.h | 1 +
2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/linux-2.6/xfs_file.c b/fs/xfs/linux-2.6/xfs_file.c
index 67d392a..185a337 100644
--- a/fs/xfs/linux-2.6/xfs_file.c
+++ b/fs/xfs/linux-2.6/xfs_file.c
@@ -124,6 +124,33 @@ xfs_iozero(
return (-status);
}

+/*
+ * Fsync operations on directories are much simpler than on regular files,
+ * as there is no file data to flush, and thus also no need for explicit
+ * cache flush operations, and there are no non-transaction metadata updates
+ * on directories either.
+ */
+STATIC int
+xfs_dir_fsync(
+ struct file *file,
+ int datasync)
+{
+ struct xfs_inode *ip = XFS_I(file->f_mapping->host);
+ struct xfs_mount *mp = ip->i_mount;
+ xfs_lsn_t lsn = 0;
+
+ trace_xfs_dir_fsync(ip);
+
+ xfs_ilock(ip, XFS_ILOCK_SHARED);
+ if (xfs_ipincount(ip))
+ lsn = ip->i_itemp->ili_last_lsn;
+ xfs_iunlock(ip, XFS_ILOCK_SHARED);
+
+ if (!lsn)
+ return 0;
+ return _xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, NULL);
+}
+
STATIC int
xfs_file_fsync(
struct file *file,
@@ -1141,7 +1168,7 @@ const struct file_operations xfs_dir_file_operations = {
#ifdef CONFIG_COMPAT
.compat_ioctl = xfs_file_compat_ioctl,
#endif
- .fsync = xfs_file_fsync,
+ .fsync = xfs_dir_fsync,
};

static const struct vm_operations_struct xfs_file_vm_ops = {
diff --git a/fs/xfs/linux-2.6/xfs_trace.h b/fs/xfs/linux-2.6/xfs_trace.h
index d48b7a5..fae13a0 100644
--- a/fs/xfs/linux-2.6/xfs_trace.h
+++ b/fs/xfs/linux-2.6/xfs_trace.h
@@ -577,6 +577,7 @@ DEFINE_INODE_EVENT(xfs_vm_bmap);
DEFINE_INODE_EVENT(xfs_file_ioctl);
DEFINE_INODE_EVENT(xfs_file_compat_ioctl);
DEFINE_INODE_EVENT(xfs_ioctl_setattr);
+DEFINE_INODE_EVENT(xfs_dir_fsync);
DEFINE_INODE_EVENT(xfs_file_fsync);
DEFINE_INODE_EVENT(xfs_destroy_inode);
DEFINE_INODE_EVENT(xfs_write_inode);