proc: faster /proc/$PID lookup

Currently lookup for /proc/$PID first goes through spinlock and whole list
of misc /proc entries only to confirm that, yes, /proc/42 can not possibly
match random proc entry.

List is is several dozens entries long (52 entries on my setup).

None of this is necessary.

Try to convert dentry name to integer first.
If it works, it must be /proc/$PID.
If it doesn't, it must be random proc entry.

Based on patch from Al Viro.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 11375216b493b7ac69f3d994c8b9990e0e138c8a..35afb2eb4a6f5519b35c2f9696c119b97309ea93 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2780,7 +2780,7 @@ out:
 
 struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags)
 {
-       int result = 0;
+       int result = -ENOENT;
        struct task_struct *task;
        unsigned tgid;
        struct pid_namespace *ns;

diff --git a/fs/proc/root.c b/fs/proc/root.c
index 5dbadecb234da01be9cc7eb5705e71363da7dfea..574bafc41f0b7c1f77160971ebb9ca6d5a8121e6 100644 (file)
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -199,10 +199,10 @@ static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct
 
 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
 {
-       if (!proc_lookup(dir, dentry, flags))
+       if (!proc_pid_lookup(dir, dentry, flags))
                return NULL;
        
-       return proc_pid_lookup(dir, dentry, flags);
+       return proc_lookup(dir, dentry, flags);
 }
 
 static int proc_root_readdir(struct file *file, struct dir_context *ctx)