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There are a few d_obtain_alias callers that are using it to get the
root of a filesystem which may already have an alias somewhere else.
This is not the same as the filehandle-lookup case, and none of them
actually need DCACHE_DISCONNECTED set.
It isn't really a serious problem, but it would really be clearer if we
reserved DCACHE_DISCONNECTED for those cases where it's actually needed.
In the btrfs case this was causing a spurious printk from
nfsd/nfsfh.c:fh_verify when it found an unexpected DCACHE_DISCONNECTED
dentry. Josef worked around this by unsetting DCACHE_DISCONNECTED
manually in 3a0dfa6a12 "Btrfs: unset DCACHE_DISCONNECTED when mounting
default subvol", and this replaces that workaround.
Cc: Josef Bacik <jbacik@fb.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Any IS_ROOT() alias should be safe to use; there's nothing special about
DCACHE_DISCONNECTED dentries.
Note that this is in fact useful for filesystems such as btrfs which can
legimately encounter a directory with a preexisting IS_ROOT alias on a
lookup that crosses into a subvolume. (Those aliases are currently
marked DCACHE_DISCONNECTED--but not really for any good reason, and
we'll change that soon.)
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Currently if d_splice_alias finds a directory with an alias that is not
IS_ROOT or not DCACHE_DISCONNECTED, it creates a duplicate directory.
Duplicate directory dentries are unacceptable; it is better just to
error out.
(In the case of a local filesystem the most likely case is filesystem
corruption: for example, perhaps two directories point to the same child
directory, and the other parent has already been found and cached.)
Note that distributed filesystems may encounter this case in normal
operation if a remote host moves a directory to a location different
from the one we last cached in the dcache. For that reason, such
filesystems should instead use d_materialise_unique, which tries to move
the old directory alias to the right place instead of erroring out.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
d_splice_alias will d_move an IS_ROOT() directory dentry into place if
one exists. This should be safe as long as the dentry remains IS_ROOT,
but I can't see what guarantees that: once we drop the i_lock all we
hold here is the i_mutex on an unrelated parent directory.
Instead copy the logic of d_materialise_unique.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Just a trivial move to locate it near (similar) d_materialise_unique
code and save some forward references in a following patch.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull vfs updates from Al Viro:
"This the bunch that sat in -next + lock_parent() fix. This is the
minimal set; there's more pending stuff.
In particular, I really hope to get acct.c fixes merged this cycle -
we need that to deal sanely with delayed-mntput stuff. In the next
pile, hopefully - that series is fairly short and localized
(kernel/acct.c, fs/super.c and fs/namespace.c). In this pile: more
iov_iter work. Most of prereqs for ->splice_write with sane locking
order are there and Kent's dio rewrite would also fit nicely on top of
this pile"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (70 commits)
lock_parent: don't step on stale ->d_parent of all-but-freed one
kill generic_file_splice_write()
ceph: switch to iter_file_splice_write()
shmem: switch to iter_file_splice_write()
nfs: switch to iter_splice_write_file()
fs/splice.c: remove unneeded exports
ocfs2: switch to iter_file_splice_write()
->splice_write() via ->write_iter()
bio_vec-backed iov_iter
optimize copy_page_{to,from}_iter()
bury generic_file_aio_{read,write}
lustre: get rid of messing with iovecs
ceph: switch to ->write_iter()
ceph_sync_direct_write: stop poking into iov_iter guts
ceph_sync_read: stop poking into iov_iter guts
new helper: copy_page_from_iter()
fuse: switch to ->write_iter()
btrfs: switch to ->write_iter()
ocfs2: switch to ->write_iter()
xfs: switch to ->write_iter()
...
Dentry that had been through (or into) __dentry_kill() might be seen
by shrink_dentry_list(); that's normal, it'll be taken off the shrink
list and freed if __dentry_kill() has already finished. The problem
is, its ->d_parent might be pointing to already freed dentry, so
lock_parent() needs to be careful.
We need to check that dentry hasn't already gone into __dentry_kill()
*and* grab rcu_read_lock() before dropping ->d_lock - the latter makes
sure that whatever we see in ->d_parent after dropping ->d_lock it
won't be freed until we drop rcu_read_lock().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This typedef is unnecessary and should just be removed.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lock_parent() very much on purpose does nested locking of dentries, and
is careful to maintain the right order (lock parent first). But because
it didn't annotate the nested locking order, lockdep thought it might be
a deadlock on d_lock, and complained.
Add the proper annotation for the inner locking of the child dentry to
make lockdep happy.
Introduced by commit 046b961b45 ("shrink_dentry_list(): take parent's
->d_lock earlier").
Reported-and-tested-by: Josh Boyer <jwboyer@fedoraproject.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We have the same problem with ->d_lock order in the inner loop, where
we are dropping references to ancestors. Same solution, basically -
instead of using dentry_kill() we use lock_parent() (introduced in the
previous commit) to get that lock in a safe way, recheck ->d_count
(in case if lock_parent() has ended up dropping and retaking ->d_lock
and somebody managed to grab a reference during that window), trylock
the inode->i_lock and use __dentry_kill() to do the rest.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The cause of livelocks there is that we are taking ->d_lock on
dentry and its parent in the wrong order, forcing us to use
trylock on the parent's one. d_walk() takes them in the right
order, and unfortunately it's not hard to create a situation
when shrink_dentry_list() can't make progress since trylock
keeps failing, and shrink_dcache_parent() or check_submounts_and_drop()
keeps calling d_walk() disrupting the very shrink_dentry_list() it's
waiting for.
Solution is straightforward - if that trylock fails, let's unlock
the dentry itself and take locks in the right order. We need to
stabilize ->d_parent without holding ->d_lock, but that's doable
using RCU. And we'd better do that in the very beginning of the
loop in shrink_dentry_list(), since the checks on refcount, etc.
would need to be redone anyway.
That deals with a half of the problem - killing dentries on the
shrink list itself. Another one (dropping their parents) is
in the next commit.
locking parent is interesting - it would be easy to do rcu_read_lock(),
lock whatever we think is a parent, lock dentry itself and check
if the parent is still the right one. Except that we need to check
that *before* locking the dentry, or we are risking taking ->d_lock
out of order. Fortunately, once the D1 is locked, we can check if
D2->d_parent is equal to D1 without the need to lock D2; D2->d_parent
can start or stop pointing to D1 only under D1->d_lock, so taking
D1->d_lock is enough. In other words, the right solution is
rcu_read_lock/lock what looks like parent right now/check if it's
still our parent/rcu_read_unlock/lock the child.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Result will be massaged to saner shape in the next commits. It is
ugly, no questions - the point of that one is to be a provably
equivalent transformation (and it might be worth splitting a bit
more).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
It can happen only when dentry_kill() is called with unlock_on_failure
equal to 0 - other callers had dentry pinned until the moment they've
got ->d_lock and DCACHE_DENTRY_KILLED is set only after lockref_mark_dead().
IOW, only one of three call sites of dentry_kill() might end up reaching
that code. Just move it there.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Since now the shrink list is private and nobody can free the dentry while
it is on the shrink list, we can remove RCU protection from this.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Start with shrink_dcache_parent(), then scan what remains.
First of all, BUG() is very much an overkill here; we are holding
->s_umount, and hitting BUG() means that a lot of interesting stuff
will be hanging after that point (sync(2), for example). Moreover,
in cases when there had been more than one leak, we'll be better
off reporting all of them. And more than just the last component
of pathname - %pd is there for just such uses...
That was the last user of dentry_lru_del(), so kill it off...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
If we find something already on a shrink list, just increment
data->found and do nothing else. Loops in shrink_dcache_parent() and
check_submounts_and_drop() will do the right thing - everything we
did put into our list will be evicted and if there had been nothing,
but data->found got non-zero, well, we have somebody else shrinking
those guys; just try again.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
If the victim in on the shrink list, don't remove it from there.
If shrink_dentry_list() manages to remove it from the list before
we are done - fine, we'll just free it as usual. If not - mark
it with new flag (DCACHE_MAY_FREE) and leave it there.
Eventually, shrink_dentry_list() will get to it, remove the sucker
from shrink list and call dentry_kill(dentry, 0). Which is where
we'll deal with freeing.
Since now dentry_kill(dentry, 0) may happen after or during
dentry_kill(dentry, 1), we need to recognize that (by seeing
DCACHE_DENTRY_KILLED already set), unlock everything
and either free the sucker (in case DCACHE_MAY_FREE has been
set) or leave it for ongoing dentry_kill(dentry, 1) to deal with.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The part of old d_free() that dealt with actual freeing of dentry.
Taken out of dentry_kill() into a separate function.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
in non-lazy walk we need to be careful about dentry switching from
negative to positive - both ->d_flags and ->d_inode are updated,
and in some places we might see only one store. The cases where
dentry has been obtained by dcache lookup with ->i_mutex held on
parent are safe - ->d_lock and ->i_mutex provide all the barriers
we need. However, there are several places where we run into
trouble:
* do_last() fetches ->d_inode, then checks ->d_flags and
assumes that inode won't be NULL unless d_is_negative() is true.
Race with e.g. creat() - we might have fetched the old value of
->d_inode (still NULL) and new value of ->d_flags (already not
DCACHE_MISS_TYPE). Lin Ming has observed and reported the resulting
oops.
* a bunch of places checks ->d_inode for being non-NULL,
then checks ->d_flags for "is it a symlink". Race with symlink(2)
in case if our CPU sees ->d_inode update first - we see non-NULL
there, but ->d_flags still contains DCACHE_MISS_TYPE instead of
DCACHE_SYMLINK_TYPE. Result: false negative on "should we follow
link here?", with subsequent unpleasantness.
Cc: stable@vger.kernel.org # 3.13 and 3.14 need that one
Reported-and-tested-by: Lin Ming <minggr@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
If flags contain RENAME_EXCHANGE then exchange source and destination files.
There's no restriction on the type of the files; e.g. a directory can be
exchanged with a symlink.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: J. Bruce Fields <bfields@redhat.com>
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Merge tag 'v3.14' into drm-intel-next-queued
Linux 3.14
The vt-d w/a merged late in 3.14-rc needs a bit of fine-tuning, hence
backmerge.
Conflicts:
drivers/gpu/drm/i915/i915_gem_gtt.c
drivers/gpu/drm/i915/intel_ddi.c
drivers/gpu/drm/i915/intel_dp.c
All trivial adjacent lines changed type conflicts, so trivial git
doesn't even show them in the merg commit.
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
In all callchains leading to prepend_name(), the value left in *buflen
is eventually discarded unused if prepend_name() has returned a negative.
So we are free to do what prepend() does, and subtract from *buflen
*before* checking for underflow (which turns into checking the sign
of subtraction result, of course).
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Our current DRM design uses a single address_space for all users of the
same DRM device. However, there is no way to create an anonymous
address_space without an underlying inode. Therefore, we wait for the
first ->open() callback on a registered char-dev and take-over the inode
of the char-dev. This worked well so far, but has several drawbacks:
- We screw with FS internals and rely on some non-obvious invariants like
inode->i_mapping being the same as inode->i_data for char-devs.
- We don't have any address_space prior to the first ->open() from
user-space. This leads to ugly fallback code and we cannot allocate
global objects early.
As pointed out by Al-Viro, fs/anon_inode.c is *not* supposed to be used by
drivers for anonymous inode-allocation. Therefore, this patch follows the
proposed alternative solution and adds a pseudo filesystem mount-point to
DRM. We can then allocate private inodes including a private address_space
for each DRM device at initialization time.
Note that we could use:
sysfs_get_inode(sysfs_mnt->mnt_sb, drm_device->dev->kobj.sd);
to get access to the underlying sysfs-inode of a "struct device" object.
However, most of this information is currently hidden and it's not clear
whether this address_space is suitable for driver access. Thus, unless
linux allows anonymous address_space objects or driver-core provides a
public inode per device, we're left with our own private internal mount
point.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
* we need to save the starting point for restarts
* reject pathologically short buffers outright
Spotted-by: Denys Vlasenko <dvlasenk@redhat.com>
Spotted-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In commit 232d2d60aa
Author: Waiman Long <Waiman.Long@hp.com>
Date: Mon Sep 9 12:18:13 2013 -0400
dcache: Translating dentry into pathname without taking rename_lock
The __dentry_path locking was changed and the variable error was
intended to be moved outside of the loop. Unfortunately the inner
declaration of error was not removed. Resulting in a version of
__dentry_path that will never return an error.
Remove the problematic inner declaration of error and allow
__dentry_path to return errors once again.
Cc: stable@vger.kernel.org
Cc: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull namespace fixes from Eric Biederman:
"This is a set of 3 regression fixes.
This fixes /proc/mounts when using "ip netns add <netns>" to display
the actual mount point.
This fixes a regression in clone that broke lxc-attach.
This fixes a regression in the permission checks for mounting /proc
that made proc unmountable if binfmt_misc was in use. Oops.
My apologies for sending this pull request so late. Al Viro gave
interesting review comments about the d_path fix that I wanted to
address in detail before I sent this pull request. Unfortunately a
bad round of colds kept from addressing that in detail until today.
The executive summary of the review was:
Al: Is patching d_path really sufficient?
The prepend_path, d_path, d_absolute_path, and __d_path family of
functions is a really mess.
Me: Yes, patching d_path is really sufficient. Yes, the code is mess.
No it is not appropriate to rewrite all of d_path for a regression
that has existed for entirely too long already, when a two line
change will do"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
vfs: Fix a regression in mounting proc
fork: Allow CLONE_PARENT after setns(CLONE_NEWPID)
vfs: In d_path don't call d_dname on a mount point
When explicitly hashing the end of a string with the word-at-a-time
interface, we have to be careful which end of the word we pick up.
On big-endian CPUs, the upper-bits will contain the data we're after, so
ensure we generate our masks accordingly (and avoid hashing whatever
random junk may have been sitting after the string).
This patch adds a new dcache helper, bytemask_from_count, which creates
a mask appropriate for the CPU endianness.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Aditya Kali (adityakali@google.com) wrote:
> Commit bf056bfa80:
> "proc: Fix the namespace inode permission checks." converted
> the namespace files into symlinks. The same commit changed
> the way namespace bind mounts appear in /proc/mounts:
> $ mount --bind /proc/self/ns/ipc /mnt/ipc
> Originally:
> $ cat /proc/mounts | grep ipc
> proc /mnt/ipc proc rw,nosuid,nodev,noexec 0 0
>
> After commit bf056bfa80:
> $ cat /proc/mounts | grep ipc
> proc ipc:[4026531839] proc rw,nosuid,nodev,noexec 0 0
>
> This breaks userspace which expects the 2nd field in
> /proc/mounts to be a valid path.
The symlink /proc/<pid>/ns/{ipc,mnt,net,pid,user,uts} point to
dentries allocated with d_alloc_pseudo that we can mount, and
that have interesting names printed out with d_dname.
When these files are bind mounted /proc/mounts is not currently
displaying the mount point correctly because d_dname is called instead
of just displaying the path where the file is mounted.
Solve this by adding an explicit check to distinguish mounted pseudo
inodes and unmounted pseudo inodes. Unmounted pseudo inodes always
use mount of their filesstem as the mnt_root in their path making
these two cases easy to distinguish.
CC: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Reported-by: Aditya Kali <adityakali@google.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
There used to be a bunch of tree-walkers in dcache.c, all alike.
try_to_ascend() had been introduced to abstract a piece of logics
duplicated in all of them. These days all these tree-walkers are
implemented via the same iterator (d_walk()), which is the only
remaining caller of try_to_ascend(), so let's fold it back...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
D_HASH{MASK,BITS} are used once each, both in the same function (d_hash()).
At this point they are actively misguiding - they imply that values are
compiler constants, which is no longer true.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull core locking changes from Ingo Molnar:
"The biggest changes:
- add lockdep support for seqcount/seqlocks structures, this
unearthed both bugs and required extra annotation.
- move the various kernel locking primitives to the new
kernel/locking/ directory"
* 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits)
block: Use u64_stats_init() to initialize seqcounts
locking/lockdep: Mark __lockdep_count_forward_deps() as static
lockdep/proc: Fix lock-time avg computation
locking/doc: Update references to kernel/mutex.c
ipv6: Fix possible ipv6 seqlock deadlock
cpuset: Fix potential deadlock w/ set_mems_allowed
seqcount: Add lockdep functionality to seqcount/seqlock structures
net: Explicitly initialize u64_stats_sync structures for lockdep
locking: Move the percpu-rwsem code to kernel/locking/
locking: Move the lglocks code to kernel/locking/
locking: Move the rwsem code to kernel/locking/
locking: Move the rtmutex code to kernel/locking/
locking: Move the semaphore core to kernel/locking/
locking: Move the spinlock code to kernel/locking/
locking: Move the lockdep code to kernel/locking/
locking: Move the mutex code to kernel/locking/
hung_task debugging: Add tracepoint to report the hang
x86/locking/kconfig: Update paravirt spinlock Kconfig description
lockstat: Report avg wait and hold times
lockdep, x86/alternatives: Drop ancient lockdep fixup message
...
Pull vfs updates from Al Viro:
"All kinds of stuff this time around; some more notable parts:
- RCU'd vfsmounts handling
- new primitives for coredump handling
- files_lock is gone
- Bruce's delegations handling series
- exportfs fixes
plus misc stuff all over the place"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (101 commits)
ecryptfs: ->f_op is never NULL
locks: break delegations on any attribute modification
locks: break delegations on link
locks: break delegations on rename
locks: helper functions for delegation breaking
locks: break delegations on unlink
namei: minor vfs_unlink cleanup
locks: implement delegations
locks: introduce new FL_DELEG lock flag
vfs: take i_mutex on renamed file
vfs: rename I_MUTEX_QUOTA now that it's not used for quotas
vfs: don't use PARENT/CHILD lock classes for non-directories
vfs: pull ext4's double-i_mutex-locking into common code
exportfs: fix quadratic behavior in filehandle lookup
exportfs: better variable name
exportfs: move most of reconnect_path to helper function
exportfs: eliminate unused "noprogress" counter
exportfs: stop retrying once we race with rename/remove
exportfs: clear DISCONNECTED on all parents sooner
exportfs: more detailed comment for path_reconnect
...
DCACHE_DISCONNECTED should not be cleared until we're sure the dentry is
connected all the way up to the root of the filesystem. It *shouldn't*
be cleared as soon as the dentry is connected to a parent. That will
cause bugs at least on exportable filesystems.
Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
I can't for the life of me see any reason why anyone should care whether
a dentry that is never hooked into the dentry cache would need
DCACHE_DISCONNECTED set.
This originates from 4b936885ab "fs:
improve scalability of pseudo filesystems", which probably just made the
false assumption the DCACHE_DISCONNECTED was meant to be set on anything
not connected to a parent somehow.
So this is just confusing. Ideally the only uses of DCACHE_DISCONNECTED
would be in the filehandle-lookup code, which needs it to ensure
dentries are connected into the dentry tree before use.
I left d_alloc_pseudo there even though it's now equivalent to
__d_alloc(), just on the theory the name is better documentation of its
intended use outside dcache.c.
Cc: Nick Piggin <npiggin@kernel.dk>
Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Every hashed dentry is either hashed in the dentry_hashtable, or a
superblock's s_anon list.
__d_drop() assumes it can determine which is the case by checking
DCACHE_DISCONNECTED; this is not true.
It is true that when DCACHE_DISCONNECTED is cleared, the dentry is not
only hashed on dentry_hashtable, but is fully connected to its parents
back to the root.
But the converse is *not* true: fs/exportfs/expfs.c:reconnect_path()
attempts to connect a directory (found by filehandle lookup) back to
root by ascending to parents and performing lookups one at a time. It
does not clear DCACHE_DISCONNECTED until it's done, and that is not at
all an atomic process.
In particular, it is possible for DCACHE_DISCONNECTED to be set on a
dentry which is hashed on the dentry_hashtable.
Instead, use IS_ROOT() to check which hash chain a dentry is on. This
*does* work:
Dentries are hashed only by:
- d_obtain_alias, which adds an IS_ROOT() dentry to sb_anon.
- __d_rehash, called by _d_rehash: hashes to the dentry's
parent, and all callers of _d_rehash appear to have d_parent
set to a "real" parent.
- __d_rehash, called by __d_move: rehashes the moved dentry to
hash chain determined by target, and assigns target's d_parent
to its d_parent, before dropping the dentry's d_lock.
Therefore I believe it's safe for a holder of a dentry's d_lock to
assume that it is hashed on sb_anon if and only if IS_ROOT(dentry) is
true.
I believe the incorrect assumption about DCACHE_DISCONNECTED was
originally introduced by ceb5bdc2d2 "fs: dcache per-bucket dcache hash
locking".
Also add a comment while we're here.
Cc: Nick Piggin <npiggin@kernel.dk>
Acked-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Put a type field into struct dentry::d_flags to indicate if the dentry is one
of the following types that relate particularly to pathwalk:
Miss (negative dentry)
Directory
"Automount" directory (defective - no i_op->lookup())
Symlink
Other (regular, socket, fifo, device)
The type field is set to one of the first five types on a dentry by calls to
__d_instantiate() and d_obtain_alias() from information in the inode (if one is
given).
The type is cleared by dentry_unlink_inode() when it reconstitutes an existing
dentry as a negative dentry.
Accessors provided are:
d_set_type(dentry, type)
d_is_directory(dentry)
d_is_autodir(dentry)
d_is_symlink(dentry)
d_is_file(dentry)
d_is_negative(dentry)
d_is_positive(dentry)
A bunch of checks in pathname resolution switched to those.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* RCU-delayed freeing of vfsmounts
* vfsmount_lock replaced with a seqlock (mount_lock)
* sequence number from mount_lock is stored in nameidata->m_seq and
used when we exit RCU mode
* new vfsmount flag - MNT_SYNC_UMOUNT. Set by umount_tree() when its
caller knows that vfsmount will have no surviving references.
* synchronize_rcu() done between unlocking namespace_sem in namespace_unlock()
and doing pending mntput().
* new helper: legitimize_mnt(mnt, seq). Checks the mount_lock sequence
number against seq, then grabs reference to mnt. Then it rechecks mount_lock
again to close the race and either returns success or drops the reference it
has acquired. The subtle point is that in case of MNT_SYNC_UMOUNT we can
simply decrement the refcount and sod off - aforementioned synchronize_rcu()
makes sure that final mntput() won't come until we leave RCU mode. We need
that, since we don't want to end up with some lazy pathwalk racing with
umount() and stealing the final mntput() from it - caller of umount() may
expect it to return only once the fs is shut down and we don't want to break
that. In other cases (i.e. with MNT_SYNC_UMOUNT absent) we have to do
full-blown mntput() in case of mount_lock sequence number mismatch happening
just as we'd grabbed the reference, but in those cases we won't be stealing
the final mntput() from anything that would care.
* mntput_no_expire() doesn't lock anything on the fast path now. Incidentally,
SMP and UP cases are handled the same way - no ifdefs there.
* normal pathname resolution does *not* do any writes to mount_lock. It does,
of course, bump the refcounts of vfsmount and dentry in the very end, but that's
it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Currently seqlocks and seqcounts don't support lockdep.
After running across a seqcount related deadlock in the timekeeping
code, I used a less-refined and more focused variant of this patch
to narrow down the cause of the issue.
This is a first-pass attempt to properly enable lockdep functionality
on seqlocks and seqcounts.
Since seqcounts are used in the vdso gettimeofday code, I've provided
non-lockdep accessors for those needs.
I've also handled one case where there were nested seqlock writers
and there may be more edge cases.
Comments and feedback would be appreciated!
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Link: http://lkml.kernel.org/r/1381186321-4906-3-git-send-email-john.stultz@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
