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Commit 518de9b3 authored by Eric Dumazet's avatar Eric Dumazet Committed by Linus Torvalds
Browse files

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: default avatarRobin Holt <holt@sgi.com>
Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Acked-by: default avatarDavid Miller <davem@davemloft.net>
Reviewed-by: default avatarRobin Holt <holt@sgi.com>
Tested-by: default avatarRobin Holt <holt@sgi.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 571428be

fs/file_table.c

+7 −10
Original line number Diff line number Diff line
@@ -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 @@ void mark_files_ro(struct super_block *sb) 


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);

include/linux/fs.h

+4 −4
Original line number Diff line number Diff line
@@ -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;

kernel/sysctl.c

+3 −3
Original line number Diff line number Diff line
@@ -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",

net/unix/af_unix.c

+7 −7
Original line number Diff line number Diff line
@@ -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);