[PATCH] locks: new procfs lockinfo

[Davidlohr Bueso <dave@gnu.org>]

From: Davidlohr Bueso <dave@gnu.org>

Based on our previous discussion https://lkml.org/lkml/2012/2/10/462 we came to
agree on deprecating the current /proc/locks in favor of a more extensible interface.
The new /proc/lockinfo file exports similar information - except instead of maj:min the
device name is shown - and entries are formated like those in /proc/cpuinfo, allowing us
to add new entries without breaking userspace.

Signed-off-by: Davidlohr Bueso <dave@gnu.org>
---
 Documentation/feature-removal-schedule.txt |    9 +++
 fs/locks.c                                 |  109 ++++++++++++++++++++++++++--
 2 files changed, 113 insertions(+), 5 deletions(-)

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index a0ffac0..1c5e14b 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -524,3 +524,12 @@ Files:	arch/arm/mach-at91/at91cap9.c
 Why:	The code is not actively maintained and platforms are now hard to find.
 Who:	Nicolas Ferre <nicolas.ferre@atmel.com>
 	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
+
+---------------------------
+
+What:	/proc/locks
+When:	2014
+Why:	The current /proc/locks file does not allow modifying entries as it breaks
+        userspace (most notably lslk(8)). A new /proc/lockinfo interface replaces
+        this file in a more extendable format (lines per entry), like /proc/cpuinfo.
+Who:	Davidlohr Bueso <dave@gnu.org>
diff --git a/fs/locks.c b/fs/locks.c
index 637694b..f7b27fe 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -112,6 +112,9 @@
  *  Leases and LOCK_MAND
  *  Matthew Wilcox <willy@debian.org>, June, 2000.
  *  Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
+ *
+ *  Deprecated /proc/locks in favor of /proc/lockinfo
+ *  Davidlohr Bueso <dave@gnu.org>, February, 2012.
  */
 
 #include <linux/capability.h>
@@ -2156,6 +2159,10 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
 	struct inode *inode = NULL;
 	unsigned int fl_pid;
 
+	/* deprecated, see Documentation/feature-removal-schedule.txt */
+	printk_once(KERN_WARNING "%s (%d): /proc/locks is deprecated please use /proc/lockinfo instead.\n",
+		    current->comm, task_pid_nr(current));
+
 	if (fl->fl_nspid)
 		fl_pid = pid_vnr(fl->fl_nspid);
 	else
@@ -2199,15 +2206,10 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
 			       : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
 	}
 	if (inode) {
-#ifdef WE_CAN_BREAK_LSLK_NOW
-		seq_printf(f, "%d %s:%ld ", fl_pid,
-				inode->i_sb->s_id, inode->i_ino);
-#else
 		/* userspace relies on this representation of dev_t ;-( */
 		seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
 				MAJOR(inode->i_sb->s_dev),
 				MINOR(inode->i_sb->s_dev), inode->i_ino);
-#endif
 	} else {
 		seq_printf(f, "%d <none>:0 ", fl_pid);
 	}
@@ -2275,9 +2277,106 @@ static const struct file_operations proc_locks_operations = {
 	.release	= seq_release_private,
 };
 
+static void lockinfo_get_status(struct seq_file *f, struct file_lock *fl,
+				loff_t id)
+{
+	struct inode *inode = NULL;
+	unsigned int fl_pid;
+
+	if (fl->fl_nspid)
+		fl_pid = pid_vnr(fl->fl_nspid);
+	else
+		fl_pid = fl->fl_pid;
+
+	if (fl->fl_file != NULL)
+		inode = fl->fl_file->f_path.dentry->d_inode;
+
+	if (IS_POSIX(fl)) {
+		seq_printf(f, "Personality:\t %s\n",
+			   (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ");
+		seq_printf(f, "Type:\t\t %s\n",
+			   (!inode) ? "*NOINODE*" : mandatory_lock(inode)
+			   ? "MANDATORY" : "ADVISORY ");
+	} else if (IS_FLOCK(fl)) {
+		seq_printf(f, "Personality:\t FLOCK\n");
+		seq_printf(f, "Type:\t\t %s\n",
+			   (fl->fl_type & LOCK_MAND) ? "MSNFS" : "ADVISORY");
+	} else if (IS_LEASE(fl)) {
+		seq_printf(f, "Personality:\t LEASE\n");
+		seq_printf(f, "Type:\t\t %s\n",
+			   (lease_breaking(fl)) ? "BREAKING"
+			   : (fl->fl_file) ? "ACTIVE" : "BREAKER");
+	} else {
+		seq_printf(f, "Personality:\t UNKNOWN\n");
+		seq_printf(f, "Type:\t\t UNKNOWN\n");
+	}
+
+	if (fl->fl_type & LOCK_MAND) {
+		seq_printf(f, "Access:\t\t %s\n",
+			   (fl->fl_type & LOCK_READ)
+			   ? (fl->fl_type & LOCK_WRITE) ? "RW   " : "READ "
+			   : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
+	} else {
+		seq_printf(f, "Access:\t\t %s\n",
+			   (lease_breaking(fl))
+			   ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
+			   : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
+	}
+
+	seq_printf(f, "PID:\t\t %d\n", fl_pid);
+
+	if (inode) {
+		seq_printf(f, "Device:\t\t %s\n",  inode->i_sb->s_id);
+		seq_printf(f, "Inode:\t\t %ld\n", inode->i_ino);
+	}
+
+	if (IS_POSIX(fl)) {
+		if (fl->fl_end == OFFSET_MAX)
+			seq_printf(f, "Start-end:\t %Ld-EOF\n\n", fl->fl_start);
+		else
+			seq_printf(f, "Start-end:\t %Ld-%Ld\n\n", fl->fl_start, fl->fl_end);
+	} else {
+		seq_printf(f, "Start-end:\t 0-EOF\n\n");
+	}
+}
+
+static int lockinfo_show(struct seq_file *f, void *v)
+{
+	struct file_lock *fl, *bfl;
+
+	fl = list_entry(v, struct file_lock, fl_link);
+
+	lockinfo_get_status(f, fl, *((loff_t *)f->private));
+
+	list_for_each_entry(bfl, &fl->fl_block, fl_block)
+		lockinfo_get_status(f, bfl, *((loff_t *)f->private));
+
+	return 0;
+}
+
+static const struct seq_operations lockinfo_seq_operations = {
+	.start	= locks_start,
+	.next	= locks_next,
+	.stop	= locks_stop,
+	.show	= lockinfo_show,
+};
+
+static int lockinfo_open(struct inode *inode, struct file *filp)
+{
+	return seq_open_private(filp, &lockinfo_seq_operations, sizeof(loff_t));
+}
+
+static const struct file_operations proc_lockinfo_operations = {
+	.open		= lockinfo_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release,
+};
+
 static int __init proc_locks_init(void)
 {
 	proc_create("locks", 0, NULL, &proc_locks_operations);
+	proc_create("lockinfo", 0, NULL, &proc_lockinfo_operations);
 	return 0;
 }
 module_init(proc_locks_init);
-- 
1.7.4.1