proc: faster /proc/$PID lookup (335eb531) · Commits · 戴 / test

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>

fs/proc/base.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;

fs/proc/root.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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)

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