From 65b6f3403431cd43ef7b0dab679a50f770124a65 Mon Sep 17 00:00:00 2001 From: Joel Becker Date: Tue, 26 Jan 2010 22:14:20 -0800 Subject: ocfs2_dlmfs: Use poll() to signify BASTs. o2dlm's userspace filesystem is an easy way to use the DLM from userspace. It is intentionally simple. For example, it does not allow for asynchronous behavior or lock conversion. This is intentional to keep the interface simple. Because there is no asynchronous notification, there is no way for a process holding a lock to know another node needs the lock. This is the number one complaint of ocfs2_dlmfs users. Turns out, we can solve this very easily. We add poll() support to ocfs2_dlmfs. When a BAST is received, the lock's file descriptor will receive POLLIN. This is trivial to implement. Userdlm already has an appropriate waitqueue, and the lock knows when it is blocked. We add the "bast" capability to tell userspace this is available. Signed-off-by: Joel Becker Acked-by: Mark Fasheh Signed-off-by: Joel Becker --- fs/ocfs2/dlm/dlmfs.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) (limited to 'fs/ocfs2/dlm') diff --git a/fs/ocfs2/dlm/dlmfs.c b/fs/ocfs2/dlm/dlmfs.c index 77d0df42fe02..ddf55dafba2d 100644 --- a/fs/ocfs2/dlm/dlmfs.c +++ b/fs/ocfs2/dlm/dlmfs.c @@ -43,6 +43,7 @@ #include #include #include +#include #include @@ -98,8 +99,12 @@ static const struct dlm_protocol_version user_locking_protocol = { * The ABI features are local to this machine's dlmfs mount. This is * distinct from the locking protocol, which is concerned with inter-node * interaction. + * + * Capabilities: + * - bast : POLLIN against the file descriptor of a held lock + * signifies a bast fired on the lock. */ -#define DLMFS_CAPABILITIES "" +#define DLMFS_CAPABILITIES "bast" extern int param_set_dlmfs_capabilities(const char *val, struct kernel_param *kp) { @@ -215,6 +220,22 @@ static int dlmfs_file_release(struct inode *inode, return 0; } +static unsigned int dlmfs_file_poll(struct file *file, poll_table *wait) +{ + int event = 0; + struct inode *inode = file->f_path.dentry->d_inode; + struct dlmfs_inode_private *ip = DLMFS_I(inode); + + poll_wait(file, &ip->ip_lockres.l_event, wait); + + spin_lock(&ip->ip_lockres.l_lock); + if (ip->ip_lockres.l_flags & USER_LOCK_BLOCKED) + event = POLLIN | POLLRDNORM; + spin_unlock(&ip->ip_lockres.l_lock); + + return event; +} + static ssize_t dlmfs_file_read(struct file *filp, char __user *buf, size_t count, @@ -585,6 +606,7 @@ static int dlmfs_fill_super(struct super_block * sb, static const struct file_operations dlmfs_file_operations = { .open = dlmfs_file_open, .release = dlmfs_file_release, + .poll = dlmfs_file_poll, .read = dlmfs_file_read, .write = dlmfs_file_write, }; -- cgit v1.2.2