[PATCH] get rid of NR_OPEN and introduce a sysctl_nr_open
- From: Eric Dumazet <dada1@xxxxxxxxxxxxx>
- Date: Tue, 27 Nov 2007 08:09:19 +0100
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 ++++++++++
fs/file.c | 8 +++++---
include/linux/fs.h | 2 +-
kernel/sys.c | 2 +-
kernel/sysctl.c | 8 ++++++++
6 files changed, 33 insertions(+), 5 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/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,
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