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  1. 18 8月, 2010 1 次提交
    • N
      fs: brlock vfsmount_lock · 99b7db7b
      由 Nick Piggin 提交于 
      fs: brlock vfsmount_lock

Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.

A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.

The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).

The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.

Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NNick Piggin <npiggin@kernel.dk>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      99b7db7b
  3. 11 8月, 2010 2 次提交
  5. 10 8月, 2010 1 次提交
    • A
      Fix sget() race with failing mount · 7a4dec53
      由 Al Viro 提交于 
      If sget() finds a matching superblock being set up, it'll
grab an active reference to it and grab s_umount.  That's
fine - we'll wait for completion of foofs_get_sb() that way.
However, if said foofs_get_sb() fails we'll end up holding
the halfway-created superblock.  deactivate_locked_super()
called by foofs_get_sb() will just unlock the sucker since
we are holding another active reference to it.

What we need is a way to tell if superblock has been successfully
set up.  Unfortunately, neither ->s_root nor the check for
MS_ACTIVE quite fit.  Cheap and easy way, suitable for backport:
new flag set by the (only) caller of ->get_sb().  If that flag
isn't present by the time sget() grabbed s_umount on preexisting
superblock it has found, it's seeing a stillborn and should
just bury it with deactivate_locked_super() (and repeat the search).

Longer term we want to set that flag in ->get_sb() instances (and
check for it to distinguish between "sget() found us a live sb"
and "sget() has allocated an sb, we need to set it up" in there,
instead of checking ->s_root as we do now).
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Cc: stable@kernel.org
      7a4dec53
  7. 28 7月, 2010 2 次提交
  9. 15 5月, 2010 1 次提交
    • A
      Fix the regression created by "set S_DEAD on unlink()..." commit · d83c49f3
      由 Al Viro 提交于 
      1) i_flags simply doesn't work for mount/unlink race prevention;
we may have many links to file and rm on one of those obviously
shouldn't prevent bind on top of another later on.  To fix it
right way we need to mark _dentry_ as unsuitable for mounting
upon; new flag (DCACHE_CANT_MOUNT) is protected by d_flags and
i_mutex on the inode in question.  Set it (with dont_mount(dentry))
in unlink/rmdir/etc., check (with cant_mount(dentry)) in places
in namespace.c that used to check for S_DEAD.  Setting S_DEAD
is still needed in places where we used to set it (for directories
getting killed), since we rely on it for readdir/rmdir race
prevention.

2) rename()/mount() protection has another bogosity - we unhash
the target before we'd checked that it's not a mountpoint.  Fixed.

3) ancient bogosity in pivot_root() - we locked i_mutex on the
right directory, but checked S_DEAD on the different (and wrong)
one.  Noticed and fixed.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      d83c49f3
  11. 12 4月, 2010 6 次提交
  13. 04 3月, 2010 7 次提交
  15. 17 1月, 2010 4 次提交
  17. 18 12月, 2009 1 次提交
    • L
      Revert "fix mismerge with Trond's stuff (create_mnt_ns() export is gone now)" · a2770d86
      由 Linus Torvalds 提交于 
      This reverts commit e9496ff4. Quoth Al:

 "it's dependent on a lot of other stuff not currently in mainline
  and badly broken with current fs/namespace.c.  Sorry, badly
  out-of-order cherry-pick from old queue.

  PS: there's a large pending series reworking the refcounting and
  lifetime rules for vfsmounts that will, among other things, allow to
  rip a subtree away _without_ dissolving connections in it, to be
  garbage-collected when all active references are gone.  It's
  considerably saner wrt "is the subtree busy" logics, but it's nowhere
  near being ready for merge at the moment; this changeset is one of the
  things becoming possible with that sucker, but it certainly shouldn't
  have been picked during this cycle.  My apologies..."
Noticed-by: NEric Paris <eparis@redhat.com>
Requested-by: NAl Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a2770d86
  19. 17 12月, 2009 1 次提交
  21. 12 10月, 2009 1 次提交
  23. 24 9月, 2009 1 次提交
    • V
      fs: fix overflow in sys_mount() for in-kernel calls · eca6f534
      由 Vegard Nossum 提交于 
      sys_mount() reads/copies a whole page for its "type" parameter.  When
do_mount_root() passes a kernel address that points to an object which is
smaller than a whole page, copy_mount_options() will happily go past this
memory object, possibly dereferencing "wild" pointers that could be in any
state (hence the kmemcheck warning, which shows that parts of the next
page are not even allocated).

(The likelihood of something going wrong here is pretty low -- first of
all this only applies to kernel calls to sys_mount(), which are mostly
found in the boot code.  Secondly, I guess if the page was not mapped,
exact_copy_from_user() _would_ in fact handle it correctly because of its
access_ok(), etc.  checks.)

But it is much nicer to avoid the dubious reads altogether, by stopping as
soon as we find a NUL byte.  Is there a good reason why we can't do
something like this, using the already existing strndup_from_user()?

[akpm@linux-foundation.org: make copy_mount_string() static]
[AV: fix compat mount breakage, which involves undoing akpm's change above]
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: Nal <al@dizzy.pdmi.ras.ru>
      eca6f534
  25. 08 8月, 2009 1 次提交
  27. 09 7月, 2009 1 次提交
  29. 24 6月, 2009 2 次提交
  31. 23 6月, 2009 2 次提交
    • T
      VFS: Add VFS helper functions for setting up private namespaces · cf8d2c11
      由 Trond Myklebust 提交于 
      The purpose of this patch is to improve the remote mount path lookup
support for distributed filesystems such as the NFSv4 client.

When given a mount command of the form "mount server:/foo/bar /mnt", the
NFSv4 client is required to look up the filehandle for "server:/", and
then look up each component of the remote mount path "foo/bar" in order
to find the directory that is actually going to be mounted on /mnt.
Following that remote mount path may involve following symlinks,
crossing server-side mount points and even following referrals to
filesystem volumes on other servers.

Since the standard VFS path lookup code already supports walking paths
that contain all these features (using in-kernel automounts for
following referrals) we would like to be able to reuse that rather than
duplicate the full path traversal functionality in the NFSv4 client code.

This patch therefore defines a VFS helper function create_mnt_ns(), that
sets up a temporary filesystem namespace and attaches a root filesystem to
it. It exports the create_mnt_ns() and put_mnt_ns() function for use by
filesystem modules.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      cf8d2c11
    • T
      VFS: Uninline the function put_mnt_ns() · 616511d0
      由 Trond Myklebust 提交于 
      In order to allow modules to use it without having to export vfsmount_lock.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      616511d0
  33. 12 6月, 2009 6 次提交
    • A
      Push BKL down into do_remount_sb() · 4aa98cf7
      由 Al Viro 提交于 
      [folded fix from Jiri Slaby]
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      4aa98cf7
    • A
      Push BKL down beyond VFS-only parts of do_mount() · 7f78d4cd
      由 Al Viro 提交于 
      Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      7f78d4cd
    • A
      Push BKL into do_mount() · 6fac98dd
      由 Al Viro 提交于 
      Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      6fac98dd
    • A
      dcache: extrace and use d_unlinked() · f3da392e
      由 Alexey Dobriyan 提交于 
      d_unlinked() will be used in middle-term to ban checkpointing when opened
but unlinked file is detected, and in long term, to detect such situation
and special case on it.
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      f3da392e
    • N
      fs: introduce mnt_clone_write · 96029c4e
      由 npiggin@suse.de 提交于 
      This patch speeds up lmbench lat_mmap test by about another 2% after the
first patch.

Before:
 avg = 462.286
 std = 5.46106

After:
 avg = 453.12
 std = 9.58257

(50 runs of each, stddev gives a reasonable confidence)

It does this by introducing mnt_clone_write, which avoids some heavyweight
operations of mnt_want_write if called on a vfsmount which we know already
has a write count; and mnt_want_write_file, which can call mnt_clone_write
if the file is open for write.

After these two patches, mnt_want_write and mnt_drop_write go from 7% on
the profile down to 1.3% (including mnt_clone_write).

[AV: mnt_want_write_file() should take file alone and derive mnt from it;
not only all callers have that form, but that's the only mnt about which
we know that it's already held for write if file is opened for write]

Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      96029c4e
    • N
      fs: mnt_want_write speedup · d3ef3d73
      由 npiggin@suse.de 提交于 
      This patch speeds up lmbench lat_mmap test by about 8%. lat_mmap is set up
basically to mmap a 64MB file on tmpfs, fault in its pages, then unmap it.
A microbenchmark yes, but it exercises some important paths in the mm.

Before:
 avg = 501.9
 std = 14.7773

After:
 avg = 462.286
 std = 5.46106

(50 runs of each, stddev gives a reasonable confidence, but there is quite
a bit of variation there still)

It does this by removing the complex per-cpu locking and counter-cache and
replaces it with a percpu counter in struct vfsmount. This makes the code
much simpler, and avoids spinlocks (although the msync is still pretty
costly, unfortunately). It results in about 900 bytes smaller code too. It
does increase the size of a vfsmount, however.

It should also give a speedup on large systems if CPUs are frequently operating
on different mounts (because the existing scheme has to operate on an atomic in
the struct vfsmount when switching between mounts). But I'm most interested in
the single threaded path performance for the moment.

[AV: minor cleanup]

Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      d3ef3d73