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Commit 3272c544 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

vfs: use __getname/__putname for getcwd() system call 



It's a pathname.  It should use the pathname allocators and
deallocators, and PATH_MAX instead of PAGE_SIZE.  Never mind that the
two are commonly the same.

With this, the allocations scale up nicely too, and I can do getcwd()
system calls at a rate of about 300M/s, with no lock contention
anywhere.

Of course, nobody sane does that, especially since getcwd() is
traditionally a very slow operation in Unix.  But this was also the
simplest way to benchmark the prepend_path() improvements by Waiman, and
once I saw the profiles I couldn't leave it well enough alone.

But apart from being an performance improvement (from using per-cpu slab
allocators instead of the raw page allocator), it's actually a valid and
real cleanup.

Signed-off-by: default avatarLinus "OCD" Torvalds <torvalds@linux-foundation.org>
parent ff812d72

fs/dcache.c

+5 −5
Original line number Diff line number Diff line
@@ -3049,7 +3049,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) 
{

	int error;

	struct path pwd, root;

	char *page = (char *) __get_free_page(GFP_USER);

	char *page = __getname();



	if (!page)

		return -ENOMEM;
@@ -3061,8 +3061,8 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) 
	br_read_lock(&vfsmount_lock);

	if (!d_unlinked(pwd.dentry)) {

		unsigned long len;

		char *cwd = page + PAGE_SIZE;

		int buflen = PAGE_SIZE;

		char *cwd = page + PATH_MAX;

		int buflen = PATH_MAX;



		prepend(&cwd, &buflen, "\0", 1);

		error = prepend_path(&pwd, &root, &cwd, &buflen);
@@ -3080,7 +3080,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) 
		}



		error = -ERANGE;

		len = PAGE_SIZE + page - cwd;

		len = PATH_MAX + page - cwd;

		if (len <= size) {

			error = len;

			if (copy_to_user(buf, cwd, len))
@@ -3092,7 +3092,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) 
	}



out:

	free_page((unsigned long) page);

	__putname(page);

	return error;

}