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Subject[PATCH] removes filp_count_lock and changes nr_files type to atomic_t
This patch removes filp_count_lock spinlock, used to protect files_stat.nr_files.

Just use atomic_t type and atomic_inc()/atomic_dec() operations.

This patch assumes that atomic_read() is a plain {return v->counter;} on all
architectures. (keywords : sysctl, /proc/sys/fs/file-nr, proc_dointvec)

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
diff -Nru linux-2.6.13-rc7/fs/file_table.c linux-2.6.13-rc7-ed/fs/file_table.c
--- linux-2.6.13-rc7/fs/file_table.c 2005-08-24 05:39:14.000000000 +0200
+++ linux-2.6.13-rc7-ed/fs/file_table.c 2005-08-25 10:41:00.000000000 +0200
@@ -28,29 +28,21 @@
/* public. Not pretty! */
__cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);

-static DEFINE_SPINLOCK(filp_count_lock);

/* slab constructors and destructors are called from arbitrary
- * context and must be fully threaded - use a local spinlock
- * to protect files_stat.nr_files
+ * context and must be fully threaded
*/
void filp_ctor(void * objp, struct kmem_cache_s *cachep, unsigned long cflags)
{
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);
+ atomic_inc(&files_stat.nr_files);
}
}

void filp_dtor(void * objp, struct kmem_cache_s *cachep, unsigned long dflags)
{
- unsigned long flags;
- spin_lock_irqsave(&filp_count_lock, flags);
- files_stat.nr_files--;
- spin_unlock_irqrestore(&filp_count_lock, flags);
+ atomic_dec(&files_stat.nr_files);
}

static inline void file_free(struct file *f)
@@ -70,7 +62,7 @@
/*
* Privileged users can go above max_files
*/
- if (files_stat.nr_files >= files_stat.max_files &&
+ if (atomic_read(&files_stat.nr_files) >= files_stat.max_files &&
!capable(CAP_SYS_ADMIN))
goto over;

@@ -94,10 +86,10 @@

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

diff -Nru linux-2.6.13-rc7/fs/xfs/linux-2.6/xfs_linux.h linux-2.6.13-rc7-ed/fs/xfs/linux-2.6/xfs_linux.h
--- linux-2.6.13-rc7/fs/xfs/linux-2.6/xfs_linux.h 2005-08-24 05:39:14.000000000 +0200
+++ linux-2.6.13-rc7-ed/fs/xfs/linux-2.6/xfs_linux.h 2005-08-25 10:41:00.000000000 +0200
@@ -242,7 +242,7 @@

/* IRIX uses the current size of the name cache to guess a good value */
/* - this isn't the same but is a good enough starting point for now. */
-#define DQUOT_HASH_HEURISTIC files_stat.nr_files
+#define DQUOT_HASH_HEURISTIC atomic_read(&files_stat.nr_files)

/* IRIX inodes maintain the project ID also, zero this field on Linux */
#define DEFAULT_PROJID 0
diff -Nru linux-2.6.13-rc7/include/linux/fs.h linux-2.6.13-rc7-ed/include/linux/fs.h
--- linux-2.6.13-rc7/include/linux/fs.h 2005-08-24 05:39:14.000000000 +0200
+++ linux-2.6.13-rc7-ed/include/linux/fs.h 2005-08-25 10:41:00.000000000 +0200
@@ -30,7 +30,7 @@

/* And dynamically-tunable limits and defaults: */
struct files_stat_struct {
- int nr_files; /* read only */
+ atomic_t nr_files; /* read only */
int nr_free_files; /* read only */
int max_files; /* tunable */
};
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