14 files changed, 157 insertions, 146 deletions

diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX
index 43e89b1537d9..cc10ce7dc339 100644
--- a/Documentation/00-INDEX
+++ b/Documentation/00-INDEX
@@ -145,7 +145,7 @@ fb/
 feature-removal-schedule.txt
         - list of files and features that are going to be removed.
 filesystems/
-        - directory with info on the various filesystems that Linux supports.
+        - info on the vfs and the various filesystems that Linux supports.
 firmware_class/
         - request_firmware() hotplug interface info.
 floppy.txt
@@ -230,8 +230,6 @@ local_ops.txt
         - semantics and behavior of local atomic operations.
 lockdep-design.txt
         - documentation on the runtime locking correctness validator.
-locks.txt
-        - info on file locking implementations, flock() vs. fcntl(), etc.
 logo.gif
         - full colour GIF image of Linux logo (penguin - Tux).
 logo.txt
@@ -240,8 +238,6 @@ m68k/
         - directory with info about Linux on Motorola 68k architecture.
 magic-number.txt
         - list of magic numbers used to mark/protect kernel data structures.
-mandatory.txt
-        - info on the Linux implementation of Sys V mandatory file locking.
 mca.txt
         - info on supporting Micro Channel Architecture (e.g. PS/2) systems.
 md.txt
diff --git a/Documentation/filesystems/00-INDEX b/Documentation/filesystems/00-INDEX
index 59db1bca7027..599593a17067 100644
--- a/Documentation/filesystems/00-INDEX
+++ b/Documentation/filesystems/00-INDEX
@@ -52,6 +52,10 @@ isofs.txt
         - info and mount options for the ISO 9660 (CDROM) filesystem.
 jfs.txt
         - info and mount options for the JFS filesystem.
+locks.txt
+        - info on file locking implementations, flock() vs. fcntl(), etc.
+mandatory-locking.txt
+        - info on the Linux implementation of Sys V mandatory file locking.
 ncpfs.txt
         - info on Novell Netware(tm) filesystem using NCP protocol.
 ntfs.txt
diff --git a/Documentation/locks.txt b/Documentation/filesystems/locks.txt
index e3b402ef33bd..fab857accbd6 100644
--- a/Documentation/locks.txt
+++ b/Documentation/filesystems/locks.txt
@@ -53,11 +53,11 @@ fcntl(), with all the problems that implies.
 1.3 Mandatory Locking As A Mount Option
 ---------------------------------------
 
-Mandatory locking, as described in 'Documentation/mandatory.txt' was prior
-to this release a general configuration option that was valid for all
-mounted filesystems. This had a number of inherent dangers, not the least
-of which was the ability to freeze an NFS server by asking it to read a
-file for which a mandatory lock existed.
+Mandatory locking, as described in 'Documentation/filesystems/mandatory.txt'
+was prior to this release a general configuration option that was valid for
+all mounted filesystems.  This had a number of inherent dangers, not the
+least of which was the ability to freeze an NFS server by asking it to read
+a file for which a mandatory lock existed.
 
 From this release of the kernel, mandatory locking can be turned on and off
 on a per-filesystem basis, using the mount options 'mand' and 'nomand'.
diff --git a/Documentation/mandatory.txt b/Documentation/filesystems/mandatory-locking.txt
index bc449d49eee5..0979d1d2ca8b 100644
--- a/Documentation/mandatory.txt
+++ b/Documentation/filesystems/mandatory-locking.txt
@@ -3,7 +3,26 @@
                 Andy Walker <andy@lysaker.kvaerner.no>
 
                            15 April 1996
-
+                     (Updated September 2007)
+
+0. Why you should avoid mandatory locking
+-----------------------------------------
+
+The Linux implementation is prey to a number of difficult-to-fix race
+conditions which in practice make it not dependable:
+
+        - The write system call checks for a mandatory lock only once
+          at its start.  It is therefore possible for a lock request to
+          be granted after this check but before the data is modified.
+          A process may then see file data change even while a mandatory
+          lock was held.
+        - Similarly, an exclusive lock may be granted on a file after
+          the kernel has decided to proceed with a read, but before the
+          read has actually completed, and the reading process may see
+          the file data in a state which should not have been visible
+          to it.
+        - Similar races make the claimed mutual exclusion between lock
+          and mmap similarly unreliable.
 
 1. What is  mandatory locking?
 ------------------------------
diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 2a40c2946d0a..716691689fd5 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -105,7 +105,7 @@ static int v9fs_file_lock(struct file *filp, int cmd, struct file_lock *fl)
         P9_DPRINTK(P9_DEBUG_VFS, "filp: %p lock: %p\n", filp, fl);
 
         /* No mandatory locks */
-        if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
+        if (__mandatory_lock(inode))
                 return -ENOLCK;
 
         if ((IS_SETLK(cmd) || IS_SETLKW(cmd)) && fl->fl_type != F_UNLCK) {
diff --git a/fs/afs/flock.c b/fs/afs/flock.c
index af6952e39a18..210acafe4a9b 100644
--- a/fs/afs/flock.c
+++ b/fs/afs/flock.c
@@ -524,8 +524,7 @@ int afs_lock(struct file *file, int cmd, struct file_lock *fl)
                (long long) fl->fl_start, (long long) fl->fl_end);
 
         /* AFS doesn't support mandatory locks */
-        if ((vnode->vfs_inode.i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
-            fl->fl_type != F_UNLCK)
+        if (__mandatory_lock(&vnode->vfs_inode) && fl->fl_type != F_UNLCK)
                 return -ENOLCK;
 
         if (IS_GETLK(cmd))
diff --git a/fs/gfs2/ops_file.c b/fs/gfs2/ops_file.c
index 46a9e10ff17b..7eb4b280ac66 100644
--- a/fs/gfs2/ops_file.c
+++ b/fs/gfs2/ops_file.c
@@ -535,7 +535,7 @@ static int gfs2_lock(struct file *file, int cmd, struct file_lock *fl)
 
         if (!(fl->fl_flags & FL_POSIX))
                 return -ENOLCK;
-        if ((ip->i_inode.i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
+        if (__mandatory_lock(&ip->i_inode))
                 return -ENOLCK;
 
         if (sdp->sd_args.ar_localflocks) {
@@ -636,7 +636,7 @@ static int gfs2_flock(struct file *file, int cmd, struct file_lock *fl)
 
         if (!(fl->fl_flags & FL_FLOCK))
                 return -ENOLCK;
-        if ((ip->i_inode.i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
+        if (__mandatory_lock(&ip->i_inode))
                 return -ENOLCK;
 
         if (sdp->sd_args.ar_localflocks)
diff --git a/fs/locks.c b/fs/locks.c
index c795eaaf6c4c..7f9a3ea47418 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -534,7 +534,9 @@ static void locks_insert_block(struct file_lock *blocker,
 static void locks_wake_up_blocks(struct file_lock *blocker)
 {
         while (!list_empty(&blocker->fl_block)) {
-                struct file_lock *waiter = list_entry(blocker->fl_block.next,
+                struct file_lock *waiter;
+
+                waiter = list_first_entry(&blocker->fl_block,
                                 struct file_lock, fl_block);
                 __locks_delete_block(waiter);
                 if (waiter->fl_lmops && waiter->fl_lmops->fl_notify)
@@ -668,7 +670,7 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
         for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
                 if (!IS_POSIX(cfl))
                         continue;
-                if (posix_locks_conflict(cfl, fl))
+                if (posix_locks_conflict(fl, cfl))
                         break;
         }
         if (cfl)
@@ -698,13 +700,12 @@ EXPORT_SYMBOL(posix_test_lock);
 static int posix_locks_deadlock(struct file_lock *caller_fl,
                                 struct file_lock *block_fl)
 {
-        struct list_head *tmp;
+        struct file_lock *fl;
 
 next_task:
         if (posix_same_owner(caller_fl, block_fl))
                 return 1;
-        list_for_each(tmp, &blocked_list) {
-                struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
+        list_for_each_entry(fl, &blocked_list, fl_link) {
                 if (posix_same_owner(fl, block_fl)) {
                         fl = fl->fl_next;
                         block_fl = fl;
@@ -715,8 +716,7 @@ next_task:
 }
 
 /* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
- * at the head of the list, but that's secret knowledge known only to
- * flock_lock_file and posix_lock_file.
+ * after any leases, but before any posix locks.
  *
  * Note that if called with an FL_EXISTS argument, the caller may determine
  * whether or not a lock was successfully freed by testing the return
@@ -733,6 +733,15 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
         lock_kernel();
         if (request->fl_flags & FL_ACCESS)
                 goto find_conflict;
+
+        if (request->fl_type != F_UNLCK) {
+                error = -ENOMEM;
+                new_fl = locks_alloc_lock();
+                if (new_fl == NULL)
+                        goto out;
+                error = 0;
+        }
+
         for_each_lock(inode, before) {
                 struct file_lock *fl = *before;
                 if (IS_POSIX(fl))
@@ -754,10 +763,6 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
                 goto out;
         }
 
-        error = -ENOMEM;
-        new_fl = locks_alloc_lock();
-        if (new_fl == NULL)
-                goto out;
         /*
          * If a higher-priority process was blocked on the old file lock,
          * give it the opportunity to lock the file.
@@ -819,7 +824,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
         lock_kernel();
         if (request->fl_type != F_UNLCK) {
                 for_each_lock(inode, before) {
-                        struct file_lock *fl = *before;
+                        fl = *before;
                         if (!IS_POSIX(fl))
                                 continue;
                         if (!posix_locks_conflict(request, fl))
@@ -1113,7 +1118,7 @@ int locks_mandatory_area(int read_write, struct inode *inode,
                          * If we've been sleeping someone might have
                          * changed the permissions behind our back.
                          */
-                        if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
+                        if (__mandatory_lock(inode))
                                 continue;
                 }
 
@@ -1337,6 +1342,7 @@ int fcntl_getlease(struct file *filp)
 int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
 {
         struct file_lock *fl, **before, **my_before = NULL, *lease;
+        struct file_lock *new_fl = NULL;
         struct dentry *dentry = filp->f_path.dentry;
         struct inode *inode = dentry->d_inode;
         int error, rdlease_count = 0, wrlease_count = 0;
@@ -1363,6 +1369,11 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
                 || (atomic_read(&inode->i_count) > 1)))
                 goto out;
 
+        error = -ENOMEM;
+        new_fl = locks_alloc_lock();
+        if (new_fl == NULL)
+                goto out;
+
         /*
          * At this point, we know that if there is an exclusive
          * lease on this file, then we hold it on this filp
@@ -1405,18 +1416,15 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
         if (!leases_enable)
                 goto out;
 
-        error = -ENOMEM;
-        fl = locks_alloc_lock();
-        if (fl == NULL)
-                goto out;
-
-        locks_copy_lock(fl, lease);
+        locks_copy_lock(new_fl, lease);
+        locks_insert_lock(before, new_fl);
 
-        locks_insert_lock(before, fl);
+        *flp = new_fl;
+        return 0;
 
-        *flp = fl;
-        error = 0;
 out:
+        if (new_fl != NULL)
+                locks_free_lock(new_fl);
         return error;
 }
 EXPORT_SYMBOL(generic_setlease);
@@ -1752,9 +1760,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
         /* Don't allow mandatory locks on files that may be memory mapped
          * and shared.
          */
-        if (IS_MANDLOCK(inode) &&
-            (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
-            mapping_writably_mapped(filp->f_mapping)) {
+        if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
                 error = -EAGAIN;
                 goto out;
         }
@@ -1878,9 +1884,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
         /* Don't allow mandatory locks on files that may be memory mapped
          * and shared.
          */
-        if (IS_MANDLOCK(inode) &&
-            (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
-            mapping_writably_mapped(filp->f_mapping)) {
+        if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
                 error = -EAGAIN;
                 goto out;
         }
@@ -2062,138 +2066,114 @@ int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
 
 EXPORT_SYMBOL_GPL(vfs_cancel_lock);
 
-static void lock_get_status(char* out, struct file_lock *fl, int id, char *pfx)
+#ifdef CONFIG_PROC_FS
+#include <linux/seq_file.h>
+
+static void lock_get_status(struct seq_file *f, struct file_lock *fl,
+                                                        int id, char *pfx)
 {
         struct inode *inode = NULL;
 
         if (fl->fl_file != NULL)
                 inode = fl->fl_file->f_path.dentry->d_inode;
 
-        out += sprintf(out, "%d:%s ", id, pfx);
+        seq_printf(f, "%d:%s ", id, pfx);
         if (IS_POSIX(fl)) {
-                out += sprintf(out, "%6s %s ",
+                seq_printf(f, "%6s %s ",
                              (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
                              (inode == NULL) ? "*NOINODE*" :
-                             (IS_MANDLOCK(inode) &&
-                              (inode->i_mode & (S_IXGRP | S_ISGID)) == S_ISGID) ?
-                             "MANDATORY" : "ADVISORY ");
+                             mandatory_lock(inode) ? "MANDATORY" : "ADVISORY ");
         } else if (IS_FLOCK(fl)) {
                 if (fl->fl_type & LOCK_MAND) {
-                        out += sprintf(out, "FLOCK  MSNFS     ");
+                        seq_printf(f, "FLOCK  MSNFS     ");
                 } else {
-                        out += sprintf(out, "FLOCK  ADVISORY  ");
+                        seq_printf(f, "FLOCK  ADVISORY  ");
                 }
         } else if (IS_LEASE(fl)) {
-                out += sprintf(out, "LEASE  ");
+                seq_printf(f, "LEASE  ");
                 if (fl->fl_type & F_INPROGRESS)
-                        out += sprintf(out, "BREAKING  ");
+                        seq_printf(f, "BREAKING  ");
                 else if (fl->fl_file)
-                        out += sprintf(out, "ACTIVE    ");
+                        seq_printf(f, "ACTIVE    ");
                 else
-                        out += sprintf(out, "BREAKER   ");
+                        seq_printf(f, "BREAKER   ");
         } else {
-                out += sprintf(out, "UNKNOWN UNKNOWN  ");
+                seq_printf(f, "UNKNOWN UNKNOWN  ");
         }
         if (fl->fl_type & LOCK_MAND) {
-                out += sprintf(out, "%s ",
+                seq_printf(f, "%s ",
                                (fl->fl_type & LOCK_READ)
                                ? (fl->fl_type & LOCK_WRITE) ? "RW   " : "READ "
                                : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
         } else {
-                out += sprintf(out, "%s ",
+                seq_printf(f, "%s ",
                                (fl->fl_type & F_INPROGRESS)
                                ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
                                : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
         }
         if (inode) {
 #ifdef WE_CAN_BREAK_LSLK_NOW
-                out += sprintf(out, "%d %s:%ld ", fl->fl_pid,
+                seq_printf(f, "%d %s:%ld ", fl->fl_pid,
                                 inode->i_sb->s_id, inode->i_ino);
 #else
                 /* userspace relies on this representation of dev_t ;-( */
-                out += sprintf(out, "%d %02x:%02x:%ld ", fl->fl_pid,
+                seq_printf(f, "%d %02x:%02x:%ld ", fl->fl_pid,
                                 MAJOR(inode->i_sb->s_dev),
                                 MINOR(inode->i_sb->s_dev), inode->i_ino);
 #endif
         } else {
-                out += sprintf(out, "%d <none>:0 ", fl->fl_pid);
+                seq_printf(f, "%d <none>:0 ", fl->fl_pid);
         }
         if (IS_POSIX(fl)) {
                 if (fl->fl_end == OFFSET_MAX)
-                        out += sprintf(out, "%Ld EOF\n", fl->fl_start);
+                        seq_printf(f, "%Ld EOF\n", fl->fl_start);
                 else
-                        out += sprintf(out, "%Ld %Ld\n", fl->fl_start,
-                                        fl->fl_end);
+                        seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
         } else {
-                out += sprintf(out, "0 EOF\n");
+                seq_printf(f, "0 EOF\n");
         }
 }
 
-static void move_lock_status(char **p, off_t* pos, off_t offset)
+static int locks_show(struct seq_file *f, void *v)
 {
-        int len;
-        len = strlen(*p);
-        if(*pos >= offset) {
-                /* the complete line is valid */
-                *p += len;
-                *pos += len;
-                return;
-        }
-        if(*pos+len > offset) {
-                /* use the second part of the line */
-                int i = offset-*pos;
-                memmove(*p,*p+i,len-i);
-                *p += len-i;
-                *pos += len;
-                return;
-        }
-        /* discard the complete line */
-        *pos += len;
+        struct file_lock *fl, *bfl;
+
+        fl = list_entry(v, struct file_lock, fl_link);
+
+        lock_get_status(f, fl, (long)f->private, "");
+
+        list_for_each_entry(bfl, &fl->fl_block, fl_block)
+                lock_get_status(f, bfl, (long)f->private, " ->");
+
+        f->private++;
+        return 0;
 }
 
-/**
- *      get_locks_status        -       reports lock usage in /proc/locks
- *      @buffer: address in userspace to write into
- *      @start: ?
- *      @offset: how far we are through the buffer
- *      @length: how much to read
- */
+static void *locks_start(struct seq_file *f, loff_t *pos)
+{
+        lock_kernel();
+        f->private = (void *)1;
+        return seq_list_start(&file_lock_list, *pos);
+}
 
-int get_locks_status(char *buffer, char **start, off_t offset, int length)
+static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
 {
-        struct list_head *tmp;
-        char *q = buffer;
-        off_t pos = 0;
-        int i = 0;
+        return seq_list_next(v, &file_lock_list, pos);
+}
 
-        lock_kernel();
-        list_for_each(tmp, &file_lock_list) {
-                struct list_head *btmp;
-                struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
-                lock_get_status(q, fl, ++i, "");
-                move_lock_status(&q, &pos, offset);
-
-                if(pos >= offset+length)
-                        goto done;
-
-                list_for_each(btmp, &fl->fl_block) {
-                        struct file_lock *bfl = list_entry(btmp,
-                                        struct file_lock, fl_block);
-                        lock_get_status(q, bfl, i, " ->");
-                        move_lock_status(&q, &pos, offset);
-
-                        if(pos >= offset+length)
-                                goto done;
-                }
-        }
-done:
+static void locks_stop(struct seq_file *f, void *v)
+{
         unlock_kernel();
-        *start = buffer;
-        if(q-buffer < length)
-                return (q-buffer);
-        return length;
 }
 
+struct seq_operations locks_seq_operations = {
+        .start  = locks_start,
+        .next   = locks_next,
+        .stop   = locks_stop,
+        .show   = locks_show,
+};
+#endif
+
 /**
  *      lock_may_read - checks that the region is free of locks
  *      @inode: the inode that is being read
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index c664bb921425..08c7c7387fce 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -577,8 +577,7 @@ static int nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
         nfs_inc_stats(inode, NFSIOS_VFSLOCK);
 
         /* No mandatory locks over NFS */
-        if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
-            fl->fl_type != F_UNLCK)
+        if (__mandatory_lock(inode) && fl->fl_type != F_UNLCK)
                 return -ENOLCK;
 
         if (IS_GETLK(cmd))
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 6f182d25793d..31673cd251c3 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -2035,7 +2035,7 @@ static inline int
 io_during_grace_disallowed(struct inode *inode, int flags)
 {
         return nfs4_in_grace() && (flags & (RD_STATE | WR_STATE))
-                && MANDATORY_LOCK(inode);
+                && mandatory_lock(inode);
 }
 
 /*
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index cec78c82b1f9..2a8d665b134b 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -61,12 +61,6 @@
 #define NFSDDBG_FACILITY                NFSDDBG_FILEOP
 
 
-/* We must ignore files (but only files) which might have mandatory
- * locks on them because there is no way to know if the accesser has
- * the lock.
- */
-#define IS_ISMNDLK(i)   (S_ISREG((i)->i_mode) && MANDATORY_LOCK(i))
-
 /*
  * This is a cache of readahead params that help us choose the proper
  * readahead strategy. Initially, we set all readahead parameters to 0
@@ -689,7 +683,12 @@ nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
         err = nfserr_perm;
         if (IS_APPEND(inode) && (access & MAY_WRITE))
                 goto out;
-        if (IS_ISMNDLK(inode))
+        /*
+         * We must ignore files (but only files) which might have mandatory
+         * locks on them because there is no way to know if the accesser has
+         * the lock.
+         */
+        if (S_ISREG((inode)->i_mode) && mandatory_lock(inode))
                 goto out;
 
         if (!inode->i_fop)
diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c
index b872a01ad3af..0071939c0095 100644
--- a/fs/proc/proc_misc.c
+++ b/fs/proc/proc_misc.c
@@ -66,7 +66,6 @@ extern int get_stram_list(char *);
 extern int get_filesystem_list(char *);
 extern int get_exec_domain_list(char *);
 extern int get_dma_list(char *);
-extern int get_locks_status (char *, char **, off_t, int);
 
 static int proc_calc_metrics(char *page, char **start, off_t off,
                                  int count, int *eof, int len)
@@ -624,16 +623,18 @@ static int cmdline_read_proc(char *page, char **start, off_t off,
         return proc_calc_metrics(page, start, off, count, eof, len);
 }
 
-static int locks_read_proc(char *page, char **start, off_t off,
-                                 int count, int *eof, void *data)
+static int locks_open(struct inode *inode, struct file *filp)
 {
-        int len = get_locks_status(page, start, off, count);
-
-        if (len < count)
-                *eof = 1;
-        return len;
+        return seq_open(filp, &locks_seq_operations);
 }
 
+static const struct file_operations proc_locks_operations = {
+        .open           = locks_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = seq_release,
+};
+
 static int execdomains_read_proc(char *page, char **start, off_t off,
                                  int count, int *eof, void *data)
 {
@@ -691,7 +692,6 @@ void __init proc_misc_init(void)
 #endif
                 {"filesystems", filesystems_read_proc},
                 {"cmdline",     cmdline_read_proc},
-                {"locks",       locks_read_proc},
                 {"execdomains", execdomains_read_proc},
                 {NULL,}
         };
@@ -709,6 +709,7 @@ void __init proc_misc_init(void)
                         entry->proc_fops = &proc_kmsg_operations;
         }
 #endif
+        create_seq_entry("locks", 0, &proc_locks_operations);
         create_seq_entry("devices", 0, &proc_devinfo_operations);
         create_seq_entry("cpuinfo", 0, &proc_cpuinfo_operations);
 #ifdef CONFIG_BLOCK
diff --git a/fs/read_write.c b/fs/read_write.c
index 507ddff48a9a..124693e8d3fa 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -205,7 +205,7 @@ int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count
         if (unlikely((pos < 0) || (loff_t) (pos + count) < 0))
                 goto Einval;
 
-        if (unlikely(inode->i_flock && MANDATORY_LOCK(inode))) {
+        if (unlikely(inode->i_flock && mandatory_lock(inode))) {
                 int retval = locks_mandatory_area(
                         read_write == READ ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE,
                         inode, file, pos, count);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6d760f1ad875..4a6a21077bae 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -883,6 +883,7 @@ extern int vfs_setlease(struct file *, long, struct file_lock **);
 extern int lease_modify(struct file_lock **, int);
 extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
 extern int lock_may_write(struct inode *, loff_t start, unsigned long count);
+extern struct seq_operations locks_seq_operations;
 
 struct fasync_struct {
         int     magic;
@@ -1375,12 +1376,25 @@ extern int locks_mandatory_area(int, struct inode *, struct file *, loff_t, size
  * Candidates for mandatory locking have the setgid bit set
  * but no group execute bit -  an otherwise meaningless combination.
  */
-#define MANDATORY_LOCK(inode) \
-        (IS_MANDLOCK(inode) && ((inode)->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
+
+static inline int __mandatory_lock(struct inode *ino)
+{
+        return (ino->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID;
+}
+
+/*
+ * ... and these candidates should be on MS_MANDLOCK mounted fs,
+ * otherwise these will be advisory locks
+ */
+
+static inline int mandatory_lock(struct inode *ino)
+{
+        return IS_MANDLOCK(ino) && __mandatory_lock(ino);
+}
 
 static inline int locks_verify_locked(struct inode *inode)
 {
-        if (MANDATORY_LOCK(inode))
+        if (mandatory_lock(inode))
                 return locks_mandatory_locked(inode);
         return 0;
 }
@@ -1391,7 +1405,7 @@ static inline int locks_verify_truncate(struct inode *inode,
                                     struct file *filp,
                                     loff_t size)
 {
-        if (inode->i_flock && MANDATORY_LOCK(inode))
+        if (inode->i_flock && mandatory_lock(inode))
                 return locks_mandatory_area(
                         FLOCK_VERIFY_WRITE, inode, filp,
                         size < inode->i_size ? size : inode->i_size,