[PATCH, v2] get rid of NR_OPEN and introduce a sysctl_nr_open

From: Eric Dumazet
Date: Wed Nov 28 2007 - 02:53:09 EST

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V1->V2

Some NR_OPEN were left unchanged for alpha, mips & sparc64.

As changing NR_OPEN from 1024*1024 to 16*1024*1024 was considered a litle
bit dangerous, just let it default to 1024*1024 but adds a new sysctl
to let sysadmins change this value.

Thank you

[PATCH] 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.

Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx>
Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>

Documentation/filesystems/proc.txt | 8 ++++++++
Documentation/sysctl/fs.txt | 10 ++++++++++
arch/alpha/kernel/osf_sys.c | 2 +-
arch/mips/kernel/sysirix.c | 2 +-
arch/sparc64/solaris/fs.c | 2 +-
arch/sparc64/solaris/timod.c | 6 ++++--
fs/file.c | 8 +++++---
include/linux/fs.h | 2 +-
kernel/sys.c | 2 +-
kernel/sysctl.c | 8 ++++++++
10 files changed, 40 insertions(+), 10 deletions(-)
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index dec9945..9b390d7 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -989,6 +989,14 @@ 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 aa986a3..f992543 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 6413c5f..72f9a61 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 4c477c7..22fd41e 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/solaris/fs.c b/arch/sparc64/solaris/fs.c
index 61be597..9311bfe 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 a9d32ce..f53123c 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 c5575de..5110acb 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 b3ec4a4..1cda287 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 d1fe71e..99c6ce1 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 0deed82..de22f7b 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1127,6 +1127,14 @@ 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,

Next message: Arkadiusz Miskiewicz: "Re: git guidance"
Previous message: Christoph Hellwig: "Re: [ANNOUNCE] Open-FCoE - Fibre Channel over Ethernet Project"
In reply to: Eric Dumazet: "Re: [PATCH] get rid of NR_OPEN and introduce a sysctl_nr_open"
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