get rid of NR_OPEN and introduce a sysctl_nr_open

NR_OPEN (historically set to 1024*1024) actually forbids processes to open
more than 1024*1024 handles.

Unfortunatly some production servers hit the not so 'ridiculously high
value' of 1024*1024 file descriptors per process.

Changing NR_OPEN is not considered safe because of vmalloc space potential
exhaust.

This patch introduces a new sysctl (/proc/sys/fs/nr_open) wich defaults to
1024*1024, so that admins can decide to change this limit if their workload
needs it.

[akpm@linux-foundation.org: export it for sparc64]
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

11 files changed, 41 insertions, 10 deletions

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index e2799b5fafea..5681e2fa1496 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1029,6 +1029,14 @@ nr_inodes
 Denotes the  number  of  inodes the system has allocated. This number will
 grow and shrink dynamically.
 
+nr_open
+-------
+
+Denotes the maximum number of file-handles a process can
+allocate. Default value is 1024*1024 (1048576) which should be
+enough for most machines. Actual limit depends on RLIMIT_NOFILE
+resource limit.
+
 nr_free_inodes
 --------------
 
diff --git a/Documentation/sysctl/fs.txt b/Documentation/sysctl/fs.txt
index aa986a35e994..f99254327ae5 100644
--- a/Documentation/sysctl/fs.txt
+++ b/Documentation/sysctl/fs.txt
@@ -23,6 +23,7 @@ Currently, these files are in /proc/sys/fs:
 - inode-max
 - inode-nr
 - inode-state
+- nr_open
 - overflowuid
 - overflowgid
 - suid_dumpable
@@ -91,6 +92,15 @@ usage of file handles and you don't need to increase the maximum.
 
 ==============================================================
 
+nr_open:
+
+This denotes the maximum number of file-handles a process can
+allocate. Default value is 1024*1024 (1048576) which should be
+enough for most machines. Actual limit depends on RLIMIT_NOFILE
+resource limit.
+
+==============================================================
+
 inode-max, inode-nr & inode-state:
 
 As with file handles, the kernel allocates the inode structures
diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c
index 6413c5f23226..72f9a619a66d 100644
--- a/arch/alpha/kernel/osf_sys.c
+++ b/arch/alpha/kernel/osf_sys.c
@@ -430,7 +430,7 @@ sys_getpagesize(void)
 asmlinkage unsigned long
 sys_getdtablesize(void)
 {
-        return NR_OPEN;
+        return sysctl_nr_open;
 }
 
 /*
diff --git a/arch/mips/kernel/sysirix.c b/arch/mips/kernel/sysirix.c
index 4c477c7ff74a..22fd41e946b2 100644
--- a/arch/mips/kernel/sysirix.c
+++ b/arch/mips/kernel/sysirix.c
@@ -356,7 +356,7 @@ asmlinkage int irix_syssgi(struct pt_regs *regs)
                         retval = NGROUPS_MAX;
                         goto out;
                 case 5:
-                        retval = NR_OPEN;
+                        retval = sysctl_nr_open;
                         goto out;
                 case 6:
                         retval = 1;
diff --git a/arch/sparc64/kernel/sparc64_ksyms.c b/arch/sparc64/kernel/sparc64_ksyms.c
index 60765e314bd8..8649635d6d74 100644
--- a/arch/sparc64/kernel/sparc64_ksyms.c
+++ b/arch/sparc64/kernel/sparc64_ksyms.c
@@ -277,6 +277,7 @@ EXPORT_SYMBOL(sys_getpid);
 EXPORT_SYMBOL(sys_geteuid);
 EXPORT_SYMBOL(sys_getuid);
 EXPORT_SYMBOL(sys_getegid);
+EXPORT_SYMBOL(sysctl_nr_open);
 EXPORT_SYMBOL(sys_getgid);
 EXPORT_SYMBOL(svr4_getcontext);
 EXPORT_SYMBOL(svr4_setcontext);
diff --git a/arch/sparc64/solaris/fs.c b/arch/sparc64/solaris/fs.c
index 61be597bf430..9311bfe4f2f7 100644
--- a/arch/sparc64/solaris/fs.c
+++ b/arch/sparc64/solaris/fs.c
@@ -624,7 +624,7 @@ asmlinkage int solaris_ulimit(int cmd, int val)
         case 3: /* UL_GMEMLIM */
                 return current->signal->rlim[RLIMIT_DATA].rlim_cur;
         case 4: /* UL_GDESLIM */
-                return NR_OPEN;
+                return sysctl_nr_open;
         }
         return -EINVAL;
 }
diff --git a/arch/sparc64/solaris/timod.c b/arch/sparc64/solaris/timod.c
index a9d32ceabf26..f53123c02c2b 100644
--- a/arch/sparc64/solaris/timod.c
+++ b/arch/sparc64/solaris/timod.c
@@ -859,7 +859,8 @@ asmlinkage int solaris_getmsg(unsigned int fd, u32 arg1, u32 arg2, u32 arg3)
 
         SOLD("entry");
         lock_kernel();
-        if(fd >= NR_OPEN) goto out;
+        if (fd >= sysctl_nr_open)
+                goto out;
 
         fdt = files_fdtable(current->files);
         filp = fdt->fd[fd];
@@ -927,7 +928,8 @@ asmlinkage int solaris_putmsg(unsigned int fd, u32 arg1, u32 arg2, u32 arg3)
 
         SOLD("entry");
         lock_kernel();
-        if(fd >= NR_OPEN) goto out;
+        if (fd >= sysctl_nr_open)
+                goto out;
 
         fdt = files_fdtable(current->files);
         filp = fdt->fd[fd];
diff --git a/fs/file.c b/fs/file.c
index c5575de01113..5110acb1c9ef 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -24,6 +24,8 @@ struct fdtable_defer {
         struct fdtable *next;
 };
 
+int sysctl_nr_open __read_mostly = 1024*1024;
+
 /*
  * We use this list to defer free fdtables that have vmalloced
  * sets/arrays. By keeping a per-cpu list, we avoid having to embed
@@ -147,8 +149,8 @@ static struct fdtable * alloc_fdtable(unsigned int nr)
         nr /= (1024 / sizeof(struct file *));
         nr = roundup_pow_of_two(nr + 1);
         nr *= (1024 / sizeof(struct file *));
-        if (nr > NR_OPEN)
-                nr = NR_OPEN;
+        if (nr > sysctl_nr_open)
+                nr = sysctl_nr_open;
 
         fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL);
         if (!fdt)
@@ -233,7 +235,7 @@ int expand_files(struct files_struct *files, int nr)
         if (nr < fdt->max_fds)
                 return 0;
         /* Can we expand? */
-        if (nr >= NR_OPEN)
+        if (nr >= sysctl_nr_open)
                 return -EMFILE;
 
         /* All good, so we try */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 19aab50c3b8e..109734bf6377 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -21,7 +21,7 @@
 
 /* Fixed constants first: */
 #undef NR_OPEN
-#define NR_OPEN (1024*1024)     /* Absolute upper limit on fd num */
+extern int sysctl_nr_open;
 #define INR_OPEN 1024           /* Initial setting for nfile rlimits */
 
 #define BLOCK_SIZE_BITS 10
diff --git a/kernel/sys.c b/kernel/sys.c
index 53de35fc8245..2b8e2daa9d95 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1472,7 +1472,7 @@ asmlinkage long sys_setrlimit(unsigned int resource, struct rlimit __user *rlim)
         if ((new_rlim.rlim_max > old_rlim->rlim_max) &&
             !capable(CAP_SYS_RESOURCE))
                 return -EPERM;
-        if (resource == RLIMIT_NOFILE && new_rlim.rlim_max > NR_OPEN)
+        if (resource == RLIMIT_NOFILE && new_rlim.rlim_max > sysctl_nr_open)
                 return -EPERM;
 
         retval = security_task_setrlimit(resource, &new_rlim);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 5e2ad5bf88e2..86daaa26d120 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1203,6 +1203,14 @@ static struct ctl_table fs_table[] = {
                 .proc_handler   = &proc_dointvec,
         },
         {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "nr_open",
+                .data           = &sysctl_nr_open,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec,
+        },
+        {
                 .ctl_name       = FS_DENTRY,
                 .procname       = "dentry-state",
                 .data           = &dentry_stat,