From 7bdb0d18bfd381cc5491eb95973ec5604b356c7e Mon Sep 17 00:00:00 2001 From: Tristan Ye Date: Mon, 11 Oct 2010 16:46:39 +0800 Subject: ocfs2: Add a mount option "coherency=*" to handle cluster coherency for O_DIRECT writes. Currently, the default behavior of O_DIRECT writes was allowing concurrent writing among nodes to the same file, with no cluster coherency guaranteed (no EX lock held). This can leave stale data in the cache for buffered reads on other nodes. The new mount option introduce a chance to choose two different behaviors for O_DIRECT writes: * coherency=full, as the default value, will disallow concurrent O_DIRECT writes by taking EX locks. * coherency=buffered, allow concurrent O_DIRECT writes without EX lock among nodes, which gains high performance at risk of getting stale data on other nodes. Signed-off-by: Tristan Ye Signed-off-by: Joel Becker --- fs/ocfs2/file.c | 29 +++++++++++++++++++++++++++-- 1 file changed, 27 insertions(+), 2 deletions(-) (limited to 'fs/ocfs2/file.c') diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c index 13af9937bdda..9e8cc4346b76 100644 --- a/fs/ocfs2/file.c +++ b/fs/ocfs2/file.c @@ -2225,6 +2225,8 @@ static ssize_t ocfs2_file_aio_write(struct kiocb *iocb, struct file *file = iocb->ki_filp; struct inode *inode = file->f_path.dentry->d_inode; struct ocfs2_super *osb = OCFS2_SB(inode->i_sb); + int full_coherency = !(osb->s_mount_opt & + OCFS2_MOUNT_COHERENCY_BUFFERED); mlog_entry("(0x%p, %u, '%.*s')\n", file, (unsigned int)nr_segs, @@ -2248,14 +2250,37 @@ relock: have_alloc_sem = 1; } - /* concurrent O_DIRECT writes are allowed */ - rw_level = !direct_io; + /* + * Concurrent O_DIRECT writes are allowed with + * mount_option "coherency=buffered". + */ + rw_level = (!direct_io || full_coherency); + ret = ocfs2_rw_lock(inode, rw_level); if (ret < 0) { mlog_errno(ret); goto out_sems; } + /* + * O_DIRECT writes with "coherency=full" need to take EX cluster + * inode_lock to guarantee coherency. + */ + if (direct_io && full_coherency) { + /* + * We need to take and drop the inode lock to force + * other nodes to drop their caches. Buffered I/O + * already does this in write_begin(). + */ + ret = ocfs2_inode_lock(inode, NULL, 1); + if (ret < 0) { + mlog_errno(ret); + goto out_sems; + } + + ocfs2_inode_unlock(inode, 1); + } + can_do_direct = direct_io; ret = ocfs2_prepare_inode_for_write(file, ppos, iocb->ki_left, appending, -- cgit v1.2.3