[Ubuntu PATCH] fix VFS nr_files accounting

From: Randy Dunlap
Date: Mon Jul 03 2006 - 16:44:13 EST


lkml discussion: http://thread.gmane.org/gmane.linux.kernel/385438/focus=385478

Already in -mm?

From: Dipankar Sarma <dipankar@xxxxxxxxxx>

Ubuntu patch location:
http://www.kernel.org/git/?p=linux/kernel/git/bcollins/ubuntu-dapper.git;a=commitdiff;h=5ce2ed3a63172c6ce0b97069e449960c2d538623

---
fs/dcache.c | 2 -
fs/file_table.c | 86 +++++++++++++++++------------------------------
include/linux/file.h | 2 +
include/linux/fs.h | 1
include/linux/rcupdate.h | 6 ---
kernel/rcupdate.c | 49 +++++++++++++-------------
kernel/sysctl.c | 5 --
net/unix/af_unix.c | 2 -
8 files changed, 62 insertions(+), 91 deletions(-)

--- linux-2617-g21.orig/fs/dcache.c
+++ linux-2617-g21/fs/dcache.c
@@ -1765,7 +1765,7 @@ void __init vfs_caches_init(unsigned lon
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);

filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
- SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
+ SLAB_HWCACHE_ALIGN|SLAB_PANIC, filp_ctor, filp_dtor);

dcache_init(mempages);
inode_init(mempages);
--- linux-2617-g21.orig/fs/file_table.c
+++ linux-2617-g21/fs/file_table.c
@@ -19,67 +19,52 @@
#include <linux/capability.h>
#include <linux/cdev.h>
#include <linux/fsnotify.h>
-#include <linux/sysctl.h>
-#include <linux/percpu_counter.h>
-
-#include <asm/atomic.h>

/* sysctl tunables... */
struct files_stat_struct files_stat = {
.max_files = NR_FILE
};

-/* public. Not pretty! */
-__cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
-
-static struct percpu_counter nr_files __cacheline_aligned_in_smp;
+EXPORT_SYMBOL(files_stat); /* Needed by unix.o */

-static inline void file_free_rcu(struct rcu_head *head)
-{
- struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
- kmem_cache_free(filp_cachep, f);
-}
+/* public. Not pretty! */
+ __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);

-static inline void file_free(struct file *f)
-{
- percpu_counter_dec(&nr_files);
- call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
-}
+static DEFINE_SPINLOCK(filp_count_lock);

-/*
- * Return the total number of open files in the system
+/* slab constructors and destructors are called from arbitrary
+ * context and must be fully threaded - use a local spinlock
+ * to protect files_stat.nr_files
*/
-static int get_nr_files(void)
+void filp_ctor(void *objp, struct kmem_cache *cachep, unsigned long cflags)
{
- return percpu_counter_read_positive(&nr_files);
+ if ((cflags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
+ SLAB_CTOR_CONSTRUCTOR) {
+ unsigned long flags;
+ spin_lock_irqsave(&filp_count_lock, flags);
+ files_stat.nr_files++;
+ spin_unlock_irqrestore(&filp_count_lock, flags);
+ }
}

-/*
- * Return the maximum number of open files in the system
- */
-int get_max_files(void)
+void filp_dtor(void *objp, struct kmem_cache *cachep, unsigned long dflags)
{
- return files_stat.max_files;
+ unsigned long flags;
+ spin_lock_irqsave(&filp_count_lock, flags);
+ files_stat.nr_files--;
+ spin_unlock_irqrestore(&filp_count_lock, flags);
}
-EXPORT_SYMBOL_GPL(get_max_files);

-/*
- * Handle nr_files sysctl
- */
-#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
-int proc_nr_files(ctl_table *table, int write, struct file *filp,
- void __user *buffer, size_t *lenp, loff_t *ppos)
+static inline void file_free_rcu(struct rcu_head *head)
{
- files_stat.nr_files = get_nr_files();
- return proc_dointvec(table, write, filp, buffer, lenp, ppos);
+ struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
+ kmem_cache_free(filp_cachep, f);
}
-#else
-int proc_nr_files(ctl_table *table, int write, struct file *filp,
- void __user *buffer, size_t *lenp, loff_t *ppos)
+
+static inline void file_free(struct file *f)
{
- return -ENOSYS;
+ call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
}
-#endif

/* Find an unused file structure and return a pointer to it.
* Returns NULL, if there are no more free file structures or
@@ -94,20 +79,14 @@ struct file *get_empty_filp(void)
/*
* Privileged users can go above max_files
*/
- if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
- /*
- * percpu_counters are inaccurate. Do an expensive check before
- * we go and fail.
- */
- if (percpu_counter_sum(&nr_files) >= files_stat.max_files)
- goto over;
- }
+ if (files_stat.nr_files >= files_stat.max_files &&
+ !capable(CAP_SYS_ADMIN))
+ goto over;

f = kmem_cache_alloc(filp_cachep, GFP_KERNEL);
if (f == NULL)
goto fail;

- percpu_counter_inc(&nr_files);
memset(f, 0, sizeof(*f));
if (security_file_alloc(f))
goto fail_sec;
@@ -124,10 +103,10 @@ struct file *get_empty_filp(void)

over:
/* Ran out of filps - report that */
- if (get_nr_files() > old_max) {
+ if (files_stat.nr_files > old_max) {
printk(KERN_INFO "VFS: file-max limit %d reached\n",
- get_max_files());
- old_max = get_nr_files();
+ files_stat.max_files);
+ old_max = files_stat.nr_files;
}
goto fail;

@@ -299,5 +278,4 @@ void __init files_init(unsigned long mem
if (files_stat.max_files < NR_FILE)
files_stat.max_files = NR_FILE;
files_defer_init();
- percpu_counter_init(&nr_files, 0);
}
--- linux-2617-g21.orig/include/linux/file.h
+++ linux-2617-g21/include/linux/file.h
@@ -80,6 +80,8 @@ extern void put_filp(struct file *);
extern int get_unused_fd(void);
extern void FASTCALL(put_unused_fd(unsigned int fd));
struct kmem_cache;
+extern void filp_ctor(void * objp, struct kmem_cache *cachep, unsigned long cflags);
+extern void filp_dtor(void * objp, struct kmem_cache *cachep, unsigned long dflags);

extern struct file ** alloc_fd_array(int);
extern void free_fd_array(struct file **, int);
--- linux-2617-g21.orig/include/linux/fs.h
+++ linux-2617-g21/include/linux/fs.h
@@ -34,7 +34,6 @@ struct files_stat_struct {
int max_files; /* tunable */
};
extern struct files_stat_struct files_stat;
-extern int get_max_files(void);

struct inodes_stat_t {
int nr_inodes;
--- linux-2617-g21.orig/include/linux/rcupdate.h
+++ linux-2617-g21/include/linux/rcupdate.h
@@ -98,17 +98,13 @@ struct rcu_data {
long batch; /* Batch # for current RCU batch */
struct rcu_head *nxtlist;
struct rcu_head **nxttail;
- long qlen; /* # of queued callbacks */
+ long count; /* # of queued items */
struct rcu_head *curlist;
struct rcu_head **curtail;
struct rcu_head *donelist;
struct rcu_head **donetail;
- long blimit; /* Upper limit on a processed batch */
int cpu;
struct rcu_head barrier;
-#ifdef CONFIG_SMP
- long last_rs_qlen; /* qlen during the last resched */
-#endif
};

DECLARE_PER_CPU(struct rcu_data, rcu_data);
--- linux-2617-g21.orig/kernel/rcupdate.c
+++ linux-2617-g21/kernel/rcupdate.c
@@ -66,8 +66,14 @@ static struct rcu_ctrlblk rcu_bh_ctrlblk
DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L };
DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L };

+static atomic_t rcu_barrier_cpu_count;
+static DEFINE_MUTEX(rcu_barrier_mutex);
+static struct completion rcu_barrier_completion;
+
/* Fake initialization required by compiler */
static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
+static int maxbatch = 10000;
+#if 0
static int blimit = 10;
static int qhimark = 10000;
static int qlowmark = 100;
@@ -75,10 +81,6 @@ static int qlowmark = 100;
static int rsinterval = 1000;
#endif

-static atomic_t rcu_barrier_cpu_count;
-static DEFINE_MUTEX(rcu_barrier_mutex);
-static struct completion rcu_barrier_completion;
-
#ifdef CONFIG_SMP
static void force_quiescent_state(struct rcu_data *rdp,
struct rcu_ctrlblk *rcp)
@@ -105,6 +107,7 @@ static inline void force_quiescent_state
set_need_resched();
}
#endif
+#endif

/**
* call_rcu - Queue an RCU callback for invocation after a grace period.
@@ -129,13 +132,17 @@ void fastcall call_rcu(struct rcu_head *
rdp = &__get_cpu_var(rcu_data);
*rdp->nxttail = head;
rdp->nxttail = &head->next;
- if (unlikely(++rdp->qlen > qhimark)) {
- rdp->blimit = INT_MAX;
- force_quiescent_state(rdp, &rcu_ctrlblk);
- }
+
+ if (unlikely(++rdp->count > 10000))
+ set_need_resched();
+
local_irq_restore(flags);
}

+static atomic_t rcu_barrier_cpu_count;
+static struct semaphore rcu_barrier_sema;
+static struct completion rcu_barrier_completion;
+
/**
* call_rcu_bh - Queue an RCU for invocation after a quicker grace period.
* @head: structure to be used for queueing the RCU updates.
@@ -164,12 +171,12 @@ void fastcall call_rcu_bh(struct rcu_hea
rdp = &__get_cpu_var(rcu_bh_data);
*rdp->nxttail = head;
rdp->nxttail = &head->next;
-
- if (unlikely(++rdp->qlen > qhimark)) {
- rdp->blimit = INT_MAX;
- force_quiescent_state(rdp, &rcu_bh_ctrlblk);
- }
-
+ rdp->count++;
+/*
+ * Should we directly call rcu_do_batch() here ?
+ * if (unlikely(rdp->count > 10000))
+ * rcu_do_batch(rdp);
+ */
local_irq_restore(flags);
}

@@ -241,12 +248,10 @@ static void rcu_do_batch(struct rcu_data
next = rdp->donelist = list->next;
list->func(list);
list = next;
- rdp->qlen--;
- if (++count >= rdp->blimit)
+ rdp->count--;
+ if (++count >= maxbatch)
break;
}
- if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark)
- rdp->blimit = blimit;
if (!rdp->donelist)
rdp->donetail = &rdp->donelist;
else
@@ -535,7 +540,6 @@ static void rcu_init_percpu_data(int cpu
rdp->quiescbatch = rcp->completed;
rdp->qs_pending = 0;
rdp->cpu = cpu;
- rdp->blimit = blimit;
}

static void __devinit rcu_online_cpu(int cpu)
@@ -621,12 +625,7 @@ void synchronize_rcu(void)
wait_for_completion(&rcu.completion);
}

-module_param(blimit, int, 0);
-module_param(qhimark, int, 0);
-module_param(qlowmark, int, 0);
-#ifdef CONFIG_SMP
-module_param(rsinterval, int, 0);
-#endif
+module_param(maxbatch, int, 0);
EXPORT_SYMBOL_GPL(rcu_batches_completed);
EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
EXPORT_SYMBOL_GPL(call_rcu);
--- linux-2617-g21.orig/kernel/sysctl.c
+++ linux-2617-g21/kernel/sysctl.c
@@ -49,9 +49,6 @@
#include <asm/uaccess.h>
#include <asm/processor.h>

-extern int proc_nr_files(ctl_table *table, int write, struct file *filp,
- void __user *buffer, size_t *lenp, loff_t *ppos);
-
#if defined(CONFIG_SYSCTL)

/* External variables not in a header file. */
@@ -971,7 +968,7 @@ static ctl_table fs_table[] = {
.data = &files_stat,
.maxlen = 3*sizeof(int),
.mode = 0444,
- .proc_handler = &proc_nr_files,
+ .proc_handler = &proc_dointvec,
},
{
.ctl_name = FS_MAXFILE,
--- linux-2617-g21.orig/net/unix/af_unix.c
+++ linux-2617-g21/net/unix/af_unix.c
@@ -570,7 +570,7 @@ static struct sock * unix_create1(struct
struct sock *sk = NULL;
struct unix_sock *u;

- if (atomic_read(&unix_nr_socks) >= 2*get_max_files())
+ if (atomic_read(&unix_nr_socks) >= 2*files_stat.max_files)
goto out;

sk = sk_alloc(PF_UNIX, GFP_KERNEL, &unix_proto, 1);

-
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