fs: allow for more than 2^31 files

Andrew,

Could you please review this patch, you probably are the right guy to
take it, because it crosses fs and net trees.

Note : /proc/sys/fs/file-nr is a read-only file, so this patch doesnt
depend on previous patch (sysctl: fix min/max handling in
__do_proc_doulongvec_minmax())

Thanks !

[PATCH V4] fs: allow for more than 2^31 files

Robin Holt tried to boot a 16TB system and found af_unix was overflowing
a 32bit value :

<quote>

We were seeing a failure which prevented boot.  The kernel was incapable
of creating either a named pipe or unix domain socket.  This comes down
to a common kernel function called unix_create1() which does:

        atomic_inc(&unix_nr_socks);
        if (atomic_read(&unix_nr_socks) > 2 * get_max_files())
                goto out;

The function get_max_files() is a simple return of files_stat.max_files.
files_stat.max_files is a signed integer and is computed in
fs/file_table.c's files_init().

        n = (mempages * (PAGE_SIZE / 1024)) / 10;
        files_stat.max_files = n;

In our case, mempages (total_ram_pages) is approx 3,758,096,384
(0xe0000000).  That leaves max_files at approximately 1,503,238,553.
This causes 2 * get_max_files() to integer overflow.

</quote>

Fix is to let /proc/sys/fs/file-nr & /proc/sys/fs/file-max use long
integers, and change af_unix to use an atomic_long_t instead of
atomic_t.

get_max_files() is changed to return an unsigned long.
get_nr_files() is changed to return a long.

unix_nr_socks is changed from atomic_t to atomic_long_t, while not
strictly needed to address Robin problem.

Before patch (on a 64bit kernel) :
# echo 2147483648 >/proc/sys/fs/file-max
# cat /proc/sys/fs/file-max
-18446744071562067968

After patch:
# echo 2147483648 >/proc/sys/fs/file-max
# cat /proc/sys/fs/file-max
2147483648
# cat /proc/sys/fs/file-nr
704     0       2147483648

Reported-by: Robin Holt <holt@sgi.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: David Miller <davem@davemloft.net>
Reviewed-by: Robin Holt <holt@sgi.com>
Tested-by: Robin Holt <holt@sgi.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

4 files changed, 21 insertions, 24 deletions

diff --git a/fs/file_table.c b/fs/file_table.c
index a04bdd81c11..c3dee381f1b 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -60,7 +60,7 @@ static inline void file_free(struct file *f)
 /*
  * Return the total number of open files in the system
  */
-static int get_nr_files(void)
+static long get_nr_files(void)
 {
         return percpu_counter_read_positive(&nr_files);
 }
@@ -68,7 +68,7 @@ static int get_nr_files(void)
 /*
  * Return the maximum number of open files in the system
  */
-int get_max_files(void)
+unsigned long get_max_files(void)
 {
         return files_stat.max_files;
 }
@@ -82,7 +82,7 @@ int proc_nr_files(ctl_table *table, int write,
                      void __user *buffer, size_t *lenp, loff_t *ppos)
 {
         files_stat.nr_files = get_nr_files();
-        return proc_dointvec(table, write, buffer, lenp, ppos);
+        return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
 }
 #else
 int proc_nr_files(ctl_table *table, int write,
@@ -105,7 +105,7 @@ int proc_nr_files(ctl_table *table, int write,
 struct file *get_empty_filp(void)
 {
         const struct cred *cred = current_cred();
-        static int old_max;
+        static long old_max;
         struct file * f;
 
         /*
@@ -140,8 +140,7 @@ struct file *get_empty_filp(void)
 over:
         /* Ran out of filps - report that */
         if (get_nr_files() > old_max) {
-                printk(KERN_INFO "VFS: file-max limit %d reached\n",
-                                        get_max_files());
+                pr_info("VFS: file-max limit %lu reached\n", get_max_files());
                 old_max = get_nr_files();
         }
         goto fail;
@@ -487,7 +486,7 @@ retry:
 
 void __init files_init(unsigned long mempages)
 { 
-        int n; 
+        unsigned long n;
 
         filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
                         SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
@@ -498,9 +497,7 @@ void __init files_init(unsigned long mempages)
          */ 
 
         n = (mempages * (PAGE_SIZE / 1024)) / 10;
-        files_stat.max_files = n; 
-        if (files_stat.max_files < NR_FILE)
-                files_stat.max_files = NR_FILE;
+        files_stat.max_files = max_t(unsigned long, n, NR_FILE);
         files_defer_init();
         lg_lock_init(files_lglock);
         percpu_counter_init(&nr_files, 0);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0a5d8363388..0cd6821013a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -34,9 +34,9 @@
 
 /* And dynamically-tunable limits and defaults: */
 struct files_stat_struct {
-        int nr_files;           /* read only */
-        int nr_free_files;      /* read only */
-        int max_files;          /* tunable */
+        unsigned long nr_files;         /* read only */
+        unsigned long nr_free_files;    /* read only */
+        unsigned long max_files;                /* tunable */
 };
 
 struct inodes_stat_t {
@@ -400,7 +400,7 @@ extern void __init inode_init_early(void);
 extern void __init files_init(unsigned long);
 
 extern struct files_stat_struct files_stat;
-extern int get_max_files(void);
+extern unsigned long get_max_files(void);
 extern int sysctl_nr_open;
 extern struct inodes_stat_t inodes_stat;
 extern int leases_enable, lease_break_time;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 3a45c224770..694b140852c 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1352,16 +1352,16 @@ static struct ctl_table fs_table[] = {
         {
                 .procname       = "file-nr",
                 .data           = &files_stat,
-                .maxlen         = 3*sizeof(int),
+                .maxlen         = sizeof(files_stat),
                 .mode           = 0444,
                 .proc_handler   = proc_nr_files,
         },
         {
                 .procname       = "file-max",
                 .data           = &files_stat.max_files,
-                .maxlen         = sizeof(int),
+                .maxlen         = sizeof(files_stat.max_files),
                 .mode           = 0644,
-                .proc_handler   = proc_dointvec,
+                .proc_handler   = proc_doulongvec_minmax,
         },
         {
                 .procname       = "nr_open",
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 0ebc777a666..3c95304a081 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -117,7 +117,7 @@
 
 static struct hlist_head unix_socket_table[UNIX_HASH_SIZE + 1];
 static DEFINE_SPINLOCK(unix_table_lock);
-static atomic_t unix_nr_socks = ATOMIC_INIT(0);
+static atomic_long_t unix_nr_socks;
 
 #define unix_sockets_unbound    (&unix_socket_table[UNIX_HASH_SIZE])
 
@@ -360,13 +360,13 @@ static void unix_sock_destructor(struct sock *sk)
         if (u->addr)
                 unix_release_addr(u->addr);
 
-        atomic_dec(&unix_nr_socks);
+        atomic_long_dec(&unix_nr_socks);
         local_bh_disable();
         sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
         local_bh_enable();
 #ifdef UNIX_REFCNT_DEBUG
-        printk(KERN_DEBUG "UNIX %p is destroyed, %d are still alive.\n", sk,
-                atomic_read(&unix_nr_socks));
+        printk(KERN_DEBUG "UNIX %p is destroyed, %ld are still alive.\n", sk,
+                atomic_long_read(&unix_nr_socks));
 #endif
 }
 
@@ -606,8 +606,8 @@ static struct sock *unix_create1(struct net *net, struct socket *sock)
         struct sock *sk = NULL;
         struct unix_sock *u;
 
-        atomic_inc(&unix_nr_socks);
-        if (atomic_read(&unix_nr_socks) > 2 * get_max_files())
+        atomic_long_inc(&unix_nr_socks);
+        if (atomic_long_read(&unix_nr_socks) > 2 * get_max_files())
                 goto out;
 
         sk = sk_alloc(net, PF_UNIX, GFP_KERNEL, &unix_proto);
@@ -632,7 +632,7 @@ static struct sock *unix_create1(struct net *net, struct socket *sock)
         unix_insert_socket(unix_sockets_unbound, sk);
 out:
         if (sk == NULL)
-                atomic_dec(&unix_nr_socks);
+                atomic_long_dec(&unix_nr_socks);
         else {
                 local_bh_disable();
                 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);