vfs: use __getname/__putname for getcwd() system call (3272c544) · Commits · 戴 / test

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:

Linus "OCD" Torvalds <torvalds@linux-foundation.org>

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;
		}

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