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  1. 12 7月, 2018 5 次提交
  3. 11 7月, 2018 2 次提交
  5. 06 6月, 2018 1 次提交
    • D
      vfs: change inode times to use struct timespec64 · 95582b00
      由 Deepa Dinamani 提交于 
      struct timespec is not y2038 safe. Transition vfs to use
y2038 safe struct timespec64 instead.

The change was made with the help of the following cocinelle
script. This catches about 80% of the changes.
All the header file and logic changes are included in the
first 5 rules. The rest are trivial substitutions.
I avoid changing any of the function signatures or any other
filesystem specific data structures to keep the patch simple
for review.

The script can be a little shorter by combining different cases.
But, this version was sufficient for my usecase.

virtual patch

@ depends on patch @
identifier now;
@@
- struct timespec
+ struct timespec64
  current_time ( ... )
  {
- struct timespec now = current_kernel_time();
+ struct timespec64 now = current_kernel_time64();
  ...
- return timespec_trunc(
+ return timespec64_trunc(
  ... );
  }

@ depends on patch @
identifier xtime;
@@
 struct \( iattr \| inode \| kstat \) {
 ...
-       struct timespec xtime;
+       struct timespec64 xtime;
 ...
 }

@ depends on patch @
identifier t;
@@
 struct inode_operations {
 ...
int (*update_time) (...,
-       struct timespec t,
+       struct timespec64 t,
...);
 ...
 }

@ depends on patch @
identifier t;
identifier fn_update_time =~ "update_time$";
@@
 fn_update_time (...,
- struct timespec *t,
+ struct timespec64 *t,
 ...) { ... }

@ depends on patch @
identifier t;
@@
lease_get_mtime( ... ,
- struct timespec *t
+ struct timespec64 *t
  ) { ... }

@te depends on patch forall@
identifier ts;
local idexpression struct inode *inode_node;
identifier i_xtime =~ "^i_[acm]time$";
identifier ia_xtime =~ "^ia_[acm]time$";
identifier fn_update_time =~ "update_time$";
identifier fn;
expression e, E3;
local idexpression struct inode *node1;
local idexpression struct inode *node2;
local idexpression struct iattr *attr1;
local idexpression struct iattr *attr2;
local idexpression struct iattr attr;
identifier i_xtime1 =~ "^i_[acm]time$";
identifier i_xtime2 =~ "^i_[acm]time$";
identifier ia_xtime1 =~ "^ia_[acm]time$";
identifier ia_xtime2 =~ "^ia_[acm]time$";
@@
(
(
- struct timespec ts;
+ struct timespec64 ts;
|
- struct timespec ts = current_time(inode_node);
+ struct timespec64 ts = current_time(inode_node);
)

<+... when != ts
(
- timespec_equal(&inode_node->i_xtime, &ts)
+ timespec64_equal(&inode_node->i_xtime, &ts)
|
- timespec_equal(&ts, &inode_node->i_xtime)
+ timespec64_equal(&ts, &inode_node->i_xtime)
|
- timespec_compare(&inode_node->i_xtime, &ts)
+ timespec64_compare(&inode_node->i_xtime, &ts)
|
- timespec_compare(&ts, &inode_node->i_xtime)
+ timespec64_compare(&ts, &inode_node->i_xtime)
|
ts = current_time(e)
|
fn_update_time(..., &ts,...)
|
inode_node->i_xtime = ts
|
node1->i_xtime = ts
|
ts = inode_node->i_xtime
|
<+... attr1->ia_xtime ...+> = ts
|
ts = attr1->ia_xtime
|
ts.tv_sec
|
ts.tv_nsec
|
btrfs_set_stack_timespec_sec(..., ts.tv_sec)
|
btrfs_set_stack_timespec_nsec(..., ts.tv_nsec)
|
- ts = timespec64_to_timespec(
+ ts =
...
-)
|
- ts = ktime_to_timespec(
+ ts = ktime_to_timespec64(
...)
|
- ts = E3
+ ts = timespec_to_timespec64(E3)
|
- ktime_get_real_ts(&ts)
+ ktime_get_real_ts64(&ts)
|
fn(...,
- ts
+ timespec64_to_timespec(ts)
,...)
)
...+>
(
<... when != ts
- return ts;
+ return timespec64_to_timespec(ts);
...>
)
|
- timespec_equal(&node1->i_xtime1, &node2->i_xtime2)
+ timespec64_equal(&node1->i_xtime2, &node2->i_xtime2)
|
- timespec_equal(&node1->i_xtime1, &attr2->ia_xtime2)
+ timespec64_equal(&node1->i_xtime2, &attr2->ia_xtime2)
|
- timespec_compare(&node1->i_xtime1, &node2->i_xtime2)
+ timespec64_compare(&node1->i_xtime1, &node2->i_xtime2)
|
node1->i_xtime1 =
- timespec_trunc(attr1->ia_xtime1,
+ timespec64_trunc(attr1->ia_xtime1,
...)
|
- attr1->ia_xtime1 = timespec_trunc(attr2->ia_xtime2,
+ attr1->ia_xtime1 =  timespec64_trunc(attr2->ia_xtime2,
...)
|
- ktime_get_real_ts(&attr1->ia_xtime1)
+ ktime_get_real_ts64(&attr1->ia_xtime1)
|
- ktime_get_real_ts(&attr.ia_xtime1)
+ ktime_get_real_ts64(&attr.ia_xtime1)
)

@ depends on patch @
struct inode *node;
struct iattr *attr;
identifier fn;
identifier i_xtime =~ "^i_[acm]time$";
identifier ia_xtime =~ "^ia_[acm]time$";
expression e;
@@
(
- fn(node->i_xtime);
+ fn(timespec64_to_timespec(node->i_xtime));
|
 fn(...,
- node->i_xtime);
+ timespec64_to_timespec(node->i_xtime));
|
- e = fn(attr->ia_xtime);
+ e = fn(timespec64_to_timespec(attr->ia_xtime));
)

@ depends on patch forall @
struct inode *node;
struct iattr *attr;
identifier i_xtime =~ "^i_[acm]time$";
identifier ia_xtime =~ "^ia_[acm]time$";
identifier fn;
@@
{
+ struct timespec ts;
<+...
(
+ ts = timespec64_to_timespec(node->i_xtime);
fn (...,
- &node->i_xtime,
+ &ts,
...);
|
+ ts = timespec64_to_timespec(attr->ia_xtime);
fn (...,
- &attr->ia_xtime,
+ &ts,
...);
)
...+>
}

@ depends on patch forall @
struct inode *node;
struct iattr *attr;
struct kstat *stat;
identifier ia_xtime =~ "^ia_[acm]time$";
identifier i_xtime =~ "^i_[acm]time$";
identifier xtime =~ "^[acm]time$";
identifier fn, ret;
@@
{
+ struct timespec ts;
<+...
(
+ ts = timespec64_to_timespec(node->i_xtime);
ret = fn (...,
- &node->i_xtime,
+ &ts,
...);
|
+ ts = timespec64_to_timespec(node->i_xtime);
ret = fn (...,
- &node->i_xtime);
+ &ts);
|
+ ts = timespec64_to_timespec(attr->ia_xtime);
ret = fn (...,
- &attr->ia_xtime,
+ &ts,
...);
|
+ ts = timespec64_to_timespec(attr->ia_xtime);
ret = fn (...,
- &attr->ia_xtime);
+ &ts);
|
+ ts = timespec64_to_timespec(stat->xtime);
ret = fn (...,
- &stat->xtime);
+ &ts);
)
...+>
}

@ depends on patch @
struct inode *node;
struct inode *node2;
identifier i_xtime1 =~ "^i_[acm]time$";
identifier i_xtime2 =~ "^i_[acm]time$";
identifier i_xtime3 =~ "^i_[acm]time$";
struct iattr *attrp;
struct iattr *attrp2;
struct iattr attr ;
identifier ia_xtime1 =~ "^ia_[acm]time$";
identifier ia_xtime2 =~ "^ia_[acm]time$";
struct kstat *stat;
struct kstat stat1;
struct timespec64 ts;
identifier xtime =~ "^[acmb]time$";
expression e;
@@
(
( node->i_xtime2 \| attrp->ia_xtime2 \| attr.ia_xtime2 \) = node->i_xtime1  ;
|
 node->i_xtime2 = \( node2->i_xtime1 \| timespec64_trunc(...) \);
|
 node->i_xtime2 = node->i_xtime1 = node->i_xtime3 = \(ts \| current_time(...) \);
|
 node->i_xtime1 = node->i_xtime3 = \(ts \| current_time(...) \);
|
 stat->xtime = node2->i_xtime1;
|
 stat1.xtime = node2->i_xtime1;
|
( node->i_xtime2 \| attrp->ia_xtime2 \) = attrp->ia_xtime1  ;
|
( attrp->ia_xtime1 \| attr.ia_xtime1 \) = attrp2->ia_xtime2;
|
- e = node->i_xtime1;
+ e = timespec64_to_timespec( node->i_xtime1 );
|
- e = attrp->ia_xtime1;
+ e = timespec64_to_timespec( attrp->ia_xtime1 );
|
node->i_xtime1 = current_time(...);
|
 node->i_xtime2 = node->i_xtime1 = node->i_xtime3 =
- e;
+ timespec_to_timespec64(e);
|
 node->i_xtime1 = node->i_xtime3 =
- e;
+ timespec_to_timespec64(e);
|
- node->i_xtime1 = e;
+ node->i_xtime1 = timespec_to_timespec64(e);
)
Signed-off-by: NDeepa Dinamani <deepa.kernel@gmail.com>
Cc: <anton@tuxera.com>
Cc: <balbi@kernel.org>
Cc: <bfields@fieldses.org>
Cc: <darrick.wong@oracle.com>
Cc: <dhowells@redhat.com>
Cc: <dsterba@suse.com>
Cc: <dwmw2@infradead.org>
Cc: <hch@lst.de>
Cc: <hirofumi@mail.parknet.co.jp>
Cc: <hubcap@omnibond.com>
Cc: <jack@suse.com>
Cc: <jaegeuk@kernel.org>
Cc: <jaharkes@cs.cmu.edu>
Cc: <jslaby@suse.com>
Cc: <keescook@chromium.org>
Cc: <mark@fasheh.com>
Cc: <miklos@szeredi.hu>
Cc: <nico@linaro.org>
Cc: <reiserfs-devel@vger.kernel.org>
Cc: <richard@nod.at>
Cc: <sage@redhat.com>
Cc: <sfrench@samba.org>
Cc: <swhiteho@redhat.com>
Cc: <tj@kernel.org>
Cc: <trond.myklebust@primarydata.com>
Cc: <tytso@mit.edu>
Cc: <viro@zeniv.linux.org.uk>
      95582b00
  7. 31 5月, 2018 3 次提交
  9. 29 5月, 2018 1 次提交
  11. 26 5月, 2018 2 次提交
  13. 21 5月, 2018 1 次提交
  15. 18 5月, 2018 1 次提交
  17. 14 5月, 2018 1 次提交
  19. 01 5月, 2018 1 次提交
    • K
      fasync: Fix deadlock between task-context and interrupt-context kill_fasync() · 7a107c0f
      由 Kirill Tkhai 提交于 
      I observed the following deadlock between them:

[task 1]                          [task 2]                         [task 3]
kill_fasync()                     mm_update_next_owner()           copy_process()
 spin_lock_irqsave(&fa->fa_lock)   read_lock(&tasklist_lock)        write_lock_irq(&tasklist_lock)
  send_sigio()                    <IRQ>                             ...
   read_lock(&fown->lock)         kill_fasync()                     ...
    read_lock(&tasklist_lock)      spin_lock_irqsave(&fa->fa_lock)  ...

Task 1 can't acquire read locked tasklist_lock, since there is
already task 3 expressed its wish to take the lock exclusive.
Task 2 holds the read locked lock, but it can't take the spin lock.

Also, there is possible another deadlock (which I haven't observed):

[task 1]                            [task 2]
f_getown()                          kill_fasync()
 read_lock(&f_own->lock)             spin_lock_irqsave(&fa->fa_lock,)
 <IRQ>                               send_sigio()                     write_lock_irq(&f_own->lock)
  kill_fasync()                       read_lock(&fown->lock)
   spin_lock_irqsave(&fa->fa_lock,)

Actually, we do not need exclusive fa->fa_lock in kill_fasync_rcu(),
as it guarantees fa->fa_file->f_owner integrity only. It may seem,
that it used to give a task a small possibility to receive two sequential
signals, if there are two parallel kill_fasync() callers, and task
handles the first signal fastly, but the behaviour won't become
different, since there is exclusive sighand lock in do_send_sig_info().

The patch converts fa_lock into rwlock_t, and this fixes two above
deadlocks, as rwlock is allowed to be taken from interrupt handler
by qrwlock design.
Signed-off-by: NKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: NJeff Layton <jlayton@redhat.com>
      7a107c0f
  21. 12 4月, 2018 1 次提交
  23. 10 4月, 2018 1 次提交
    • D
      vfs: Remove the const from dir_context::actor · a09acf4b
      由 David Howells 提交于 
      Remove the const marking from the actor function pointer in the dir_context
struct.  The const prevents the structure from being used as part of a
kmalloc'd object as it makes the compiler require that the actor member be
set at object initialisation time (or not at all), incuring something like
the following error if you try and set it later:

	fs/afs/dir.c:556:20: error: assignment of read-only member 'actor'

Marking the member const like this adds very little in the way of sanity
checking as the type checking system is likely to provide sufficient - and
if not, the kernel is very likely to oops repeatably in this case.

Fixes: ac6614b7 ("[readdir] constify ->actor")
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Reviewed-by: NAl Viro <viro@zeniv.linux.org.uk>
      a09acf4b
  25. 31 3月, 2018 1 次提交
  27. 28 3月, 2018 1 次提交
  29. 23 3月, 2018 1 次提交
  31. 19 3月, 2018 2 次提交
    • M
      buffer.c: call thaw_super during emergency thaw · 08fdc8a0
      由 Mateusz Guzik 提交于 
      There are 2 distinct freezing mechanisms - one operates on block
devices and another one directly on super blocks. Both end up with the
same result, but thaw of only one of these does not thaw the other.

In particular fsfreeze --freeze uses the ioctl variant going to the
super block. Since prior to this patch emergency thaw was not doing
a relevant thaw, filesystems frozen with this method remained
unaffected.

The patch is a hack which adds blind unfreezing.

In order to keep the super block write-locked the whole time the code
is shuffled around and the newly introduced __iterate_supers is
employed.
Signed-off-by: NMateusz Guzik <mguzik@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      08fdc8a0
    • R
      vfs: make sure struct filename->iname is word-aligned · 1c949843
      由 Rasmus Villemoes 提交于 
      I noticed that offsetof(struct filename, iname) is actually 28 on 64
bit platforms, so we always pass an unaligned pointer to
strncpy_from_user. This is mostly a problem for those 64 bit platforms
without HAVE_EFFICIENT_UNALIGNED_ACCESS, but even on x86_64, unaligned
accesses carry a penalty.

A user-space microbenchmark doing nothing but strncpy_from_user from the
same (aligned) source string runs about 5% faster when the destination
is aligned. That number increases to 20% when the string is long
enough (~32 bytes) that we cross a cache line boundary - that's for
example the case for about half the files a "git status" in a kernel
tree ends up stat'ing.

This won't make any real-life workloads 5%, or even 1%, faster, but path
lookup is common enough that cutting even a few cycles should be
worthwhile. So ensure we always pass an aligned destination pointer to
strncpy_from_user. Instead of explicit padding, simply swap the refcnt
and aname members, as suggested by Al Viro.
Signed-off-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      1c949843
  33. 16 3月, 2018 1 次提交
    • E
      fs: Teach path_connected to handle nfs filesystems with multiple roots. · 95dd7758
      由 Eric W. Biederman 提交于 
      On nfsv2 and nfsv3 the nfs server can export subsets of the same
filesystem and report the same filesystem identifier, so that the nfs
client can know they are the same filesystem.  The subsets can be from
disjoint directory trees.  The nfsv2 and nfsv3 filesystems provides no
way to find the common root of all directory trees exported form the
server with the same filesystem identifier.

The practical result is that in struct super s_root for nfs s_root is
not necessarily the root of the filesystem.  The nfs mount code sets
s_root to the root of the first subset of the nfs filesystem that the
kernel mounts.

This effects the dcache invalidation code in generic_shutdown_super
currently called shrunk_dcache_for_umount and that code for years
has gone through an additional list of dentries that might be dentry
trees that need to be freed to accomodate nfs.

When I wrote path_connected I did not realize nfs was so special, and
it's hueristic for avoiding calling is_subdir can fail.

The practical case where this fails is when there is a move of a
directory from the subtree exposed by one nfs mount to the subtree
exposed by another nfs mount.  This move can happen either locally or
remotely.  With the remote case requiring that the move directory be cached
before the move and that after the move someone walks the path
to where the move directory now exists and in so doing causes the
already cached directory to be moved in the dcache through the magic
of d_splice_alias.

If someone whose working directory is in the move directory or a
subdirectory and now starts calling .. from the initial mount of nfs
(where s_root == mnt_root), then path_connected as a heuristic will
not bother with the is_subdir check.  As s_root really is not the root
of the nfs filesystem this heuristic is wrong, and the path may
actually not be connected and path_connected can fail.

The is_subdir function might be cheap enough that we can call it
unconditionally.  Verifying that will take some benchmarking and
the result may not be the same on all kernels this fix needs
to be backported to.  So I am avoiding that for now.

Filesystems with snapshots such as nilfs and btrfs do something
similar.  But as the directory tree of the snapshots are disjoint
from one another and from the main directory tree rename won't move
things between them and this problem will not occur.

Cc: stable@vger.kernel.org
Reported-by: NAl Viro <viro@ZenIV.linux.org.uk>
Fixes: 397d425d ("vfs: Test for and handle paths that are unreachable from their mnt_root")
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      95dd7758
  35. 13 3月, 2018 2 次提交
  37. 27 2月, 2018 1 次提交
  39. 29 1月, 2018 3 次提交
    • D
      xfs: only grab shared inode locks for source file during reflink · 01c2e13d
      由 Darrick J. Wong 提交于 
      Reflink and dedupe operations remap blocks from a source file into a
destination file.  The destination file needs exclusive locks on all
levels because we're updating its block map, but the source file isn't
undergoing any block map changes so we can use a shared lock.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
      01c2e13d
    • J
      fs: handle inode->i_version more efficiently · f02a9ad1
      由 Jeff Layton 提交于 
      Since i_version is mostly treated as an opaque value, we can exploit that
fact to avoid incrementing it when no one is watching. With that change,
we can avoid incrementing the counter on writes, unless someone has
queried for it since it was last incremented. If the a/c/mtime don't
change, and the i_version hasn't changed, then there's no need to dirty
the inode metadata on a write.

Convert the i_version counter to an atomic64_t, and use the lowest order
bit to hold a flag that will tell whether anyone has queried the value
since it was last incremented.

When we go to maybe increment it, we fetch the value and check the flag
bit.  If it's clear then we don't need to do anything if the update
isn't being forced.

If we do need to update, then we increment the counter by 2, and clear
the flag bit, and then use a CAS op to swap it into place. If that
works, we return true. If it doesn't then do it again with the value
that we fetch from the CAS operation.

On the query side, if the flag is already set, then we just shift the
value down by 1 bit and return it. Otherwise, we set the flag in our
on-stack value and again use cmpxchg to swap it into place if it hasn't
changed. If it has, then we use the value from the cmpxchg as the new
"old" value and try again.

This method allows us to avoid incrementing the counter on writes (and
dirtying the metadata) under typical workloads. We only need to increment
if it has been queried since it was last changed.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Acked-by: NDave Chinner <dchinner@redhat.com>
Tested-by: NKrzysztof Kozlowski <krzk@kernel.org>
      f02a9ad1
    • J
      fs: new API for handling inode->i_version · ae5e165d
      由 Jeff Layton 提交于 
      Add a documentation blob that explains what the i_version field is, how
it is expected to work, and how it is currently implemented by various
filesystems.

We already have inode_inc_iversion. Add several other functions for
manipulating and accessing the i_version counter. For now, the
implementation is trivial and basically works the way that all of the
open-coded i_version accesses work today.

Future patches will convert existing users of i_version to use the new
API, and then convert the backend implementation to do things more
efficiently.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Reviewed-by: NJan Kara <jack@suse.cz>
      ae5e165d
  41. 26 1月, 2018 2 次提交
  43. 09 1月, 2018 1 次提交
    • D
      iomap: report collisions between directio and buffered writes to userspace · 5a9d929d
      由 Darrick J. Wong 提交于 
      If two programs simultaneously try to write to the same part of a file
via direct IO and buffered IO, there's a chance that the post-diowrite
pagecache invalidation will fail on the dirty page.  When this happens,
the dio write succeeded, which means that the page cache is no longer
coherent with the disk!

Programs are not supposed to mix IO types and this is a clear case of
data corruption, so store an EIO which will be reflected to userspace
during the next fsync.  Replace the WARN_ON with a ratelimited pr_crit
so that the developers have /some/ kind of breadcrumb to track down the
offending program(s) and file(s) involved.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NLiu Bo <bo.li.liu@oracle.com>
      5a9d929d
  45. 06 1月, 2018 1 次提交
  47. 26 12月, 2017 1 次提交
    • N
      VFS: don't keep disconnected dentries on d_anon · f1ee6162
      由 NeilBrown 提交于 
      The original purpose of the per-superblock d_anon list was to
keep disconnected dentries in the cache between consecutive
requests to the NFS server.  Dentries can be disconnected if
a client holds a file open and repeatedly performs IO on it,
and if the server drops the dentry, whether due to memory
pressure, server restart, or "echo 3 > /proc/sys/vm/drop_caches".

This purpose was thwarted by commit 75a6f82a ("freeing unlinked
file indefinitely delayed") which caused disconnected dentries
to be freed as soon as their refcount reached zero.

This means that, when a dentry being used by nfsd gets disconnected, a
new one needs to be allocated for every request (unless requests
overlap).  As the dentry has no name, no parent, and no children,
there is little of value to cache.  As small memory allocations are
typically fast (from per-cpu free lists) this likely has little cost.

This means that the original purpose of s_anon is no longer relevant:
there is no longer any need to keep disconnected dentries on a list so
they appear to be hashed.

However, s_anon now has a new use.  When you mount an NFS filesystem,
the dentry stored in s_root is just a placebo.  The "real" root dentry
is allocated using d_obtain_root() and so it kept on the s_anon list.
I don't know the reason for this, but suspect it related to NFSv4
where a mount of "server:/some/path" require NFS to look up the root
filehandle on the server, then walk down "/some" and "/path" to get
the filehandle to mount.

Whatever the reason, NFS depends on the s_anon list and on
shrink_dcache_for_umount() pruning all dentries on this list.  So we
cannot simply remove s_anon.

We could just leave the code unchanged, but apart from that being
potentially confusing, the (unfair) bit-spin-lock which protects
s_anon can become a bottle neck when lots of disconnected dentries are
being created.

So this patch renames s_anon to s_roots, and stops storing
disconnected dentries on the list.  Only dentries obtained with
d_obtain_root() are now stored on this list.  There are many fewer of
these (only NFS and NILFS2 use the call, and only during filesystem
mount) so contention on the bit-lock will not be a problem.

Possibly an alternate solution should be found for NFS and NILFS2, but
that would require understanding their needs first.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      f1ee6162
  49. 30 11月, 2017 2 次提交
    • I
      autofs: revert "autofs: fix AT_NO_AUTOMOUNT not being honored" · 5d38f049
      由 Ian Kent 提交于 
      Commit 42f46148 ("autofs: fix AT_NO_AUTOMOUNT not being honored")
allowed the fstatat(2) system call to properly honor the AT_NO_AUTOMOUNT
flag but introduced a semantic change.

In order to honor AT_NO_AUTOMOUNT a semantic change was made to the
negative dentry case for stat family system calls in follow_automount().

This changed the unconditional triggering of an automount in this case
to no longer be done and an error returned instead.

This has caused more problems than I expected so reverting the change is
needed.

In a discussion with Neil Brown it was concluded that the automount(8)
daemon can implement this change without kernel modifications.  So that
will be done instead and the autofs module documentation updated with a
description of the problem and what needs to be done by module users for
this specific case.

Link: http://lkml.kernel.org/r/151174730120.6162.3848002191530283984.stgit@pluto.themaw.net
Fixes: 42f46148 ("autofs: fix AT_NO_AUTOMOUNT not being honored")
Signed-off-by: NIan Kent <raven@themaw.net>
Cc: Neil Brown <neilb@suse.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Colin Walters <walters@redhat.com>
Cc: Ondrej Holy <oholy@redhat.com>
Cc: <stable@vger.kernel.org>	[4.11+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      5d38f049
    • D
      mm: introduce get_user_pages_longterm · 2bb6d283
      由 Dan Williams 提交于 
      Patch series "introduce get_user_pages_longterm()", v2.

Here is a new get_user_pages api for cases where a driver intends to
keep an elevated page count indefinitely.  This is distinct from usages
like iov_iter_get_pages where the elevated page counts are transient.
The iov_iter_get_pages cases immediately turn around and submit the
pages to a device driver which will put_page when the i/o operation
completes (under kernel control).

In the longterm case userspace is responsible for dropping the page
reference at some undefined point in the future.  This is untenable for
filesystem-dax case where the filesystem is in control of the lifetime
of the block / page and needs reasonable limits on how long it can wait
for pages in a mapping to become idle.

Fixing filesystems to actually wait for dax pages to be idle before
blocks from a truncate/hole-punch operation are repurposed is saved for
a later patch series.

Also, allowing longterm registration of dax mappings is a future patch
series that introduces a "map with lease" semantic where the kernel can
revoke a lease and force userspace to drop its page references.

I have also tagged these for -stable to purposely break cases that might
assume that longterm memory registrations for filesystem-dax mappings
were supported by the kernel.  The behavior regression this policy
change implies is one of the reasons we maintain the "dax enabled.
Warning: EXPERIMENTAL, use at your own risk" notification when mounting
a filesystem in dax mode.

It is worth noting the device-dax interface does not suffer the same
constraints since it does not support file space management operations
like hole-punch.

This patch (of 4):

Until there is a solution to the dma-to-dax vs truncate problem it is
not safe to allow long standing memory registrations against
filesytem-dax vmas.  Device-dax vmas do not have this problem and are
explicitly allowed.

This is temporary until a "memory registration with layout-lease"
mechanism can be implemented for the affected sub-systems (RDMA and
V4L2).

[akpm@linux-foundation.org: use kcalloc()]
Link: http://lkml.kernel.org/r/151068939435.7446.13560129395419350737.stgit@dwillia2-desk3.amr.corp.intel.com
Fixes: 3565fce3 ("mm, x86: get_user_pages() for dax mappings")
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Suggested-by: NChristoph Hellwig <hch@lst.de>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Hal Rosenstock <hal.rosenstock@gmail.com>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Joonyoung Shim <jy0922.shim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Sean Hefty <sean.hefty@intel.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2bb6d283
  51. 28 11月, 2017 1 次提交