* branch 'dcache-word-accesses':
vfs: use 'unsigned long' accesses for dcache name comparison and hashing
This does the name hashing and lookup using word-sized accesses when
that is efficient, namely on x86 (although any little-endian machine
with good unaligned accesses would do).
It does very much depend on little-endian logic, but it's a very hot
couple of functions under some real loads, and this patch improves the
performance of __d_lookup_rcu() and link_path_walk() by up to about 30%.
Giving a 10% improvement on some very pathname-heavy benchmarks.
Because we do make unaligned accesses past the filename, the
optimization is disabled when CONFIG_DEBUG_PAGEALLOC is active, and we
effectively depend on the fact that on x86 we don't really ever have the
last page of usable RAM followed immediately by any IO memory (due to
ACPI tables, BIOS buffer areas etc).
Some of the bit operations we do are a bit "subtle". It's commented,
but you do need to really think about the code. Or just consider it
black magic.
Thanks to people on G+ for some of the optimized bit tricks.
complete_walk() returns either ECHILD or ESTALE. do_last() turns this into
ECHILD unconditionally. If not in RCU mode, this error will reach userspace
which is complete nonsense.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
complete_walk() already puts nd->path, no need to do it again at cleanup time.
This would result in Oopses if triggered, apparently the codepath is not too
well exercised.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Ok, this is hacky, and only works on little-endian machines with goo
unaligned handling. And even then only with CONFIG_DEBUG_PAGEALLOC
disabled, since it can access up to 7 bytes after the pathname.
But it runs like a bat out of hell.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 5707c87f "vfs: uninline full_name_hash()" broke the modular
build, because it needs exporting now that it isn't inlined any more.
Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The code in link_path_walk() that finds out the length and the hash of
the next path component is some of the hottest code in the kernel. And
I have a version of it that does things at the full width of the CPU
wordsize at a time, but that means that we *really* want to split it up
into a separate helper function.
So this re-organizes the code a bit and splits the hashing part into a
helper function called "hash_name()". It returns the length of the
pathname component, while at the same time computing and writing the
hash to the appropriate location.
The code generation is slightly changed by this patch, but generally for
the better - and the added abstraction actually makes the code easier to
read too. And the new interface is well suited for replacing just the
"hash_name()" function with alternative implementations.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
.. and also use it in lookup_one_len() rather than open-coding it.
There aren't any performance-critical users, so inlining it is silly.
But it wouldn't matter if it wasn't for the fact that the word-at-a-time
dentry name patches want to conditionally replace the function, and
uninlining it sets the stage for that.
So again, this is a preparatory patch that doesn't change any semantics,
and only prepares for a much cleaner and testable word-at-a-time dentry
name accessor patch.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Just a code cleanup really. We don't need to make a function call just for
it to return on error. This also makes the VFS function even easier to follow
and removes a conditional on a hot path.
Signed-off-by: Eric Paris <eparis@redhat.com>
vfs_create() ignores everything outside of 16bit subset of its
mode argument; switching it to umode_t is obviously equivalent
and it's the only caller of the method
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
vfs_mkdir() gets int, but immediately drops everything that might not
fit into umode_t and that's the only caller of ->mkdir()...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Mountpoint crossing is similar to following procfs symlinks - we do
not get ->d_revalidate() called for dentry we have arrived at, with
unpleasant consequences for NFS4.
Simple way to reproduce the problem in mainline:
cat >/tmp/a.c <<'EOF'
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
main()
{
struct flock fl = {.l_type = F_RDLCK, .l_whence = SEEK_SET, .l_len = 1};
if (fcntl(0, F_SETLK, &fl))
perror("setlk");
}
EOF
cc /tmp/a.c -o /tmp/test
then on nfs4:
mount --bind file1 file2
/tmp/test < file1 # ok
/tmp/test < file2 # spews "setlk: No locks available"...
What happens is the missing call of ->d_revalidate() after mountpoint
crossing and that's where NFS4 would issue OPEN request to server.
The fix is simple - treat mountpoint crossing the same way we deal with
following procfs-style symlinks. I.e. set LOOKUP_JUMPED...
Cc: stable@kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since the commit below which added O_PATH support to the *at() calls, the
error return for readlink/readlinkat for the empty pathname has switched
from ENOENT to EINVAL:
commit 65cfc67223
Author: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun Mar 13 15:56:26 2011 -0400
readlinkat(), fchownat() and fstatat() with empty relative pathnames
This is both unexpected for userspace and makes readlink/readlinkat
inconsistant with all other interfaces; and inconsistant with our stated
return for these pathnames.
As the readlinkat call does not have a flags parameter we cannot use the
AT_EMPTY_PATH approach used in the other calls. Therefore expose whether
the original path is infact entry via a new user_path_at_empty() path
lookup function. Use this to determine whether to default to EINVAL or
ENOENT for failures.
Addresses http://bugs.launchpad.net/bugs/817187
[akpm@linux-foundation.org: remove unused getname_flags()]
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
In setlease, we use i_writecount to decide whether we can give out a
read lease.
In open, we break leases before incrementing i_writecount.
There is therefore a window between the break lease and the i_writecount
increment when setlease could add a new read lease.
This would leave us with a simultaneous write open and read lease, which
shouldn't happen.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
That flag no longer makes sense, since we don't look up automount points
as eagerly any more. Additionally, it turns out that the NO_AUTOMOUNT
handling was buggy to begin with: it would avoid automounting even for
cases where we really *needed* to do the automount handling, and could
return ENOENT for autofs entries that hadn't been instantiated yet.
With our new non-eager automount semantics, one discussion has been
about adding a AT_AUTOMOUNT flag to vfs_fstatat (and thus the
newfstatat() and fstatat64() system calls), but it's probably not worth
it: you can always force at least directory automounting by simply
adding the final '/' to the filename, which works for *all* of the stat
family system calls, old and new.
So AT_NO_AUTOMOUNT (and thus LOOKUP_NO_AUTOMOUNT) really were just a
result of our bad default behavior.
Acked-by: Ian Kent <raven@themaw.net>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since we've now turned around and made LOOKUP_FOLLOW *not* force an
automount, we want to add the ability to force an automount event on
lookup even if we don't happen to have one of the other flags that force
it implicitly (LOOKUP_OPEN, LOOKUP_DIRECTORY, LOOKUP_PARENT..)
Most cases will never want to use this, since you'd normally want to
delay automounting as long as possible, which usually implies
LOOKUP_OPEN (when we open a file or directory, we really cannot avoid
the automount any more).
But Trond argued sufficiently forcefully that at a minimum bind mounting
a file and quotactl will want to force the automount lookup. Some other
cases (like nfs_follow_remote_path()) could use it too, although
LOOKUP_DIRECTORY would work there as well.
This commit just adds the flag and logic, no users yet, though. It also
doesn't actually touch the LOOKUP_NO_AUTOMOUNT flag that is related, and
was made irrelevant by the same change that made us not follow on
LOOKUP_FOLLOW.
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Ian Kent <raven@themaw.net>
Cc: Jeff Layton <jlayton@redhat.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Greg KH <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We used to get the victim pinned by dentry_unhash() prior to commit
64252c75a2 ("vfs: remove dget() from dentry_unhash()") and ->rmdir()
and ->rename() instances relied on that; most of them don't care, but
ones that used d_delete() themselves do. As the result, we are getting
rmdir() oopses on NFS now.
Just grab the reference before locking the victim and drop it explicitly
after unlocking, same as vfs_rename_other() does.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Simon Kirby <sim@hostway.ca>
Cc: stable@kernel.org (3.0.x)
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Prior to 2.6.38 automount would not trigger on either stat(2) or
lstat(2) on the automount point.
After 2.6.38, with the introduction of the ->d_automount()
infrastructure, stat(2) and others would start triggering automount
while lstat(2), etc. still would not. This is a regression and a
userspace ABI change.
Problem originally reported here:
http://thread.gmane.org/gmane.linux.kernel.autofs/6098
It appears that there was an attempt at fixing various userspace tools
to not trigger the automount. But since the stat system call is
rather common it is impossible to "fix" all userspace.
This patch reverts the original behavior, which is to not trigger on
stat(2) and other symlink following syscalls.
[ It's not really clear what the right behavior is. Apparently Solaris
does the "automount on stat, leave alone on lstat". And some programs
can get unhappy when "stat+open+fstat" ends up giving a different
result from the fstat than from the initial stat.
But the change in 2.6.38 resulted in problems for some people, so
we're going back to old behavior. Maybe we can re-visit this
discussion at some future date - Linus ]
Reported-by: Leonardo Chiquitto <leonardo.lists@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Acked-by: Ian Kent <raven@themaw.net>
Cc: David Howells <dhowells@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Al points out that the do_follow_link() helper function really is
misnamed - it's about whether we should try to follow a symlink or not,
not about actually doing the following.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
After commit 3567866bf2: "RCUify freeing acls, let check_acl() go ahead in
RCU mode if acl is cached" posix_acl_permission is being called with an
unsupported flag and the permission check fails. This patch fixes the issue.
Signed-off-by: Ari Savolainen <ari.m.savolainen@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The inode structure layout is largely random, and some of the vfs paths
really do care. The path lookup in particular is already quite D$
intensive, and profiles show that accessing the 'inode->i_op->xyz'
fields is quite costly.
We already optimized the dcache to not unnecessarily load the d_op
structure for members that are often NULL using the DCACHE_OP_xyz bits
in dentry->d_flags, and this does something very similar for the inode
ops that are used during pathname lookup.
It also re-orders the fields so that the fields accessed by 'stat' are
together at the beginning of the inode structure, and roughly in the
order accessed.
The effect of this seems to be in the 1-2% range for an empty kernel
"make -j" run (which is fairly kernel-intensive, mostly in filename
lookup), so it's visible. The numbers are fairly noisy, though, and
likely depend a lot on exact microarchitecture. So there's more tuning
to be done.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Autofs may set the DCACHE_NEED_AUTOMOUNT flag on negative dentries. These
need attention from the automounter daemon regardless of the LOOKUP_FOLLOW flag.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Commit e77819e57f ("vfs: move ACL cache lookup into generic code")
didn't take the FS_POSIX_ACL config variable into account - when that is
not set, ACL's go away, and the cache helper functions do not exist,
causing compile errors like
fs/namei.c: In function 'check_acl':
fs/namei.c:191:10: error: implicit declaration of function 'negative_cached_acl'
fs/namei.c:196:2: error: implicit declaration of function 'get_cached_acl'
fs/namei.c:196:6: warning: assignment makes pointer from integer without a cast
fs/namei.c:212:11: error: implicit declaration of function 'set_cached_acl'
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The "fsuid is the inode owner" case is not necessarily always the likely
case, but it's the case that doesn't do anything odd and that we want in
straight-line code. Make gcc not generate random "jump around for the
fun of it" code.
This just helps me read profiles. That thing is one of the hottest
parts of the whole pathname lookup.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Replace the ->check_acl method with a ->get_acl method that simply reads an
ACL from disk after having a cache miss. This means we can replace the ACL
checking boilerplate code with a single implementation in namei.c.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This moves logic for checking the cached ACL values from low-level
filesystems into generic code. The end result is a streamlined ACL
check that doesn't need to load the inode->i_op->check_acl pointer at
all for the common cached case.
The filesystems also don't need to check for a non-blocking RCU walk
case in their acl_check() functions, because that is all handled at a
VFS layer.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The flags parameter went away in
d749519b444db985e40b897f73ce1898b11f997e
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
combination of kern_path_parent() and lookup_create(). Does *not*
expose struct nameidata to caller. Syscalls converted to that...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
