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Commit d0adde574b8487ef30f69e2d08bba769e4be513f added MNT_STRICTATIME
but it isn't actually used (MS_STRICTATIME clears MNT_RELATIME and
MNT_NOATIME rather than setting any mount flag).
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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This patch adds the list and mask fields needed to support vfsmount marks.
These are the same fields fsnotify needs on an inode. They are not used,
just declared and we note where the cleanup hook should be (the function is
not yet defined)
Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6: (52 commits)
init: Open /dev/console from rootfs
mqueue: fix typo "failues" -> "failures"
mqueue: only set error codes if they are really necessary
mqueue: simplify do_open() error handling
mqueue: apply mathematics distributivity on mq_bytes calculation
mqueue: remove unneeded info->messages initialization
mqueue: fix mq_open() file descriptor leak on user-space processes
fix race in d_splice_alias()
set S_DEAD on unlink() and non-directory rename() victims
vfs: add NOFOLLOW flag to umount(2)
get rid of ->mnt_parent in tomoyo/realpath
hppfs can use existing proc_mnt, no need for do_kern_mount() in there
Mirror MS_KERNMOUNT in ->mnt_flags
get rid of useless vfsmount_lock use in put_mnt_ns()
Take vfsmount_lock to fs/internal.h
get rid of insanity with namespace roots in tomoyo
take check for new events in namespace (guts of mounts_poll()) to namespace.c
Don't mess with generic_permission() under ->d_lock in hpfs
sanitize const/signedness for udf
nilfs: sanitize const/signedness in dealing with ->d_name.name
...
Fix up fairly trivial (famous last words...) conflicts in
drivers/infiniband/core/uverbs_main.c and security/tomoyo/realpath.c
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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no more users left outside of fs/*.c (and very few outside of
fs/namespace.c, actually)
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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The handling of mount flags in set_mnt_shared() got a little tangled
up during previous cleanups, with the following problems:
* MNT_PNODE_MASK is defined as a literal constant when it should be a
bitwise xor of other MNT_* flags
* set_mnt_shared() clears and then sets MNT_SHARED (part of MNT_PNODE_MASK)
* MNT_PNODE_MASK could use a comment in mount.h
* MNT_PNODE_MASK is a terrible name, change to MNT_SHARED_MASK
This patch fixes these problems.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Add __percpu sparse annotations to fs.
These annotations are to make sparse consider percpu variables to be
in a different address space and warn if accessed without going
through percpu accessors. This patch doesn't affect normal builds.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Alex Elder <aelder@sgi.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
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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: Nick Piggin <npiggin@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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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: Nick Piggin <npiggin@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Add support for explicitly requesting full atime updates. This makes it
possible for kernels to default to relatime but still allow userspace to
override it.
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Remove a CVS keyword that wasn't updated for a long time from a comment.
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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- use kstrdup() instead of kmalloc() + memcpy()
- return NULL if allocating ->mnt_devname failed
- mnt_devname should be const
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Remove the "#ifdef __KERNEL__" tests from unexported header files in
linux/include whose entire contents are wrapped in that preprocessor
test.
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add a unique ID to each peer group using the IDR infrastructure. The
identifiers are reused after the peer group dissolves.
The IDR structures are protected by holding namepspace_sem for write
while allocating or deallocating IDs.
IDs are allocated when a previously unshared vfsmount becomes the
first member of a peer group. When a new member is added to an
existing group, the ID is copied from one of the old members.
IDs are freed when the last member of a peer group is unshared.
Setting the MNT_SHARED flag on members of a subtree is done as a
separate step, after all the IDs have been allocated. This way an
allocation failure can be cleaned up easilty, without affecting the
propagation state.
Based on design sketch by Al Viro.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Add a unique ID to each vfsmount using the IDR infrastructure. The
identifiers are reused after the vfsmount is freed.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Originally from: Herbert Poetzl <herbert@13thfloor.at>
This is the core of the read-only bind mount patch set.
Note that this does _not_ add a "ro" option directly to the bind mount
operation. If you require such a mount, you must first do the bind, then
follow it up with a 'mount -o remount,ro' operation:
If you wish to have a r/o bind mount of /foo on bar:
mount --bind /foo /bar
mount -o remount,ro /bar
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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This patch adds two function mnt_want_write() and mnt_drop_write(). These are
used like a lock pair around and fs operations that might cause a write to the
filesystem.
Before these can become useful, we must first cover each place in the VFS
where writes are performed with a want/drop pair. When that is complete, we
can actually introduce code that will safely check the counts before allowing
r/w<->r/o transitions to occur.
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... and take it out of ->umount_begin() instances. Call with all locks
already taken (by do_umount()) and leave calling release_mounts() to
caller (it will do release_mounts() anyway, so we can just put into
the same list).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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make propagate_mount_busy() exclude references from the vfsmounts
that had been isolated by umount_tree() and are just waiting for
release_mounts() to dispose of their ->mnt_parent/->mnt_mountpoint.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Fix the misspellings of "propogate", "writting" and (oh, the shame
:-) "kenrel" in the source tree.
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
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I noticed cache misses in touch_atime() that can be avoided if we keep
mnt_count & mnt_expiry_mark in a different cache line than mnt_flags
(mostly read)
mnt_count & mnt_expiry_mark are modified each time a file is opened/closed
in a file system.
touch_atime() is called each time a file is read, and generally needs to
read mnt_flags.
Other fields of struct vfsmount are mostly read so I chose to move
mnt_count & mnt_expiry_mark at the end of struct vfsmount. And adding a
comment so that nobody tries to re-arrange fields to fill the holes :)
On 64bits platforms, the new offsetof(mnt_count) is 0xC0
On 32bits platforms, it is 0x60, so I didnot add a
____cacheline_aligned_in_smp because it would have a too big impact on the
size of this object (in particular if CONFIG_X86_L1_CACHE_SHIFT=7)
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add "relatime" (relative atime) support. Relative atime only updates the
atime if the previous atime is older than the mtime or ctime. Like
noatime, but useful for applications like mutt that need to know when a
file has been read since it was last modified.
A corresponding patch against mount(8) is available at
http://userweb.kernel.org/~akpm/mount-relative-atime.txt
Signed-off-by: Valerie Henson <val_henson@linux.intel.com>
Cc: Mark Fasheh <mark.fasheh@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Karel Zak <kzak@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Rename 'struct namespace' to 'struct mnt_namespace' to avoid confusion with
other namespaces being developped for the containers : pid, uts, ipc, etc.
'namespace' variables and attributes are also renamed to 'mnt_ns'
Signed-off-by: Kirill Korotaev <dev@sw.ru>
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Conflicts:
fs/nfs/inode.c
fs/super.c
Fix conflicts between patch 'NFS: Split fs/nfs/inode.c' and patch
'VFS: Permit filesystem to override root dentry on mount'
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Give the statfs superblock operation a dentry pointer rather than a superblock
pointer.
This complements the get_sb() patch. That reduced the significance of
sb->s_root, allowing NFS to place a fake root there. However, NFS does
require a dentry to use as a target for the statfs operation. This permits
the root in the vfsmount to be used instead.
linux/mount.h has been added where necessary to make allyesconfig build
successfully.
Interest has also been expressed for use with the FUSE and XFS filesystems.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Nathan Scott <nathans@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Allow a submount to be marked as being 'shrinkable' by means of the
vfsmount->mnt_flags, and then add a function 'shrink_submounts()' which
attempts to recursively unmount these submounts.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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do_kern_mount() does not allow the kernel to use private mount interfaces
without exposing the same interfaces to userland. The problem is that the
filesystem is referenced by name, thus meaning that it and its mount
interface must be registered in the global filesystem list.
vfs_kern_mount() passes the struct file_system_type as an explicit
parameter in order to overcome this limitation.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Turn noatime and nodiratime into per-mount instead of per-sb flags.
After all the preparations this is a rather trivial patch. The mount code
needs to treat the two options as per-mount instead of per-superblock, and
touch_atime needs to be changed to check the new MNT_ flags in addition to
the MS_ flags that are kept for filesystems that are always
noatime/nodiratime but not user settable anymore. Besides that core code
only nfs needed an update because it's leaving atime updates to the server
and thus sets the S_NOATIME flag on every inode, but needs to know whether
it's a real noatime mount for an getattr optimization.
While we're at it I've killed the IS_NOATIME/IS_NODIRATIME macros that were
only used by touch_atime.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Small cleanups in shared mounts code.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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An unbindable mount does not forward or receive propagation. Also
unbindable mount disallows bind mounts. The semantics is as follows.
Bind semantics:
It is invalid to bind mount an unbindable mount.
Move semantics:
It is invalid to move an unbindable mount under shared mount.
Clone-namespace semantics:
If a mount is unbindable in the parent namespace, the corresponding
cloned mount in the child namespace becomes unbindable too. Note:
there is subtle difference, unbindable mounts cannot be bind mounted
but can be cloned during clone-namespace.
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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A slave mount always has a master mount from which it receives
mount/umount events. Unlike shared mount the event propagation does not
flow from the slave mount to the master.
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This creates shared mounts. A shared mount when bind-mounted to some
mountpoint, propagates mount/umount events to each other. All the
shared mounts that propagate events to each other belong to the same
peer-group.
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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A private mount does not forward or receive propagation. This patch
provides user the ability to convert any mount to private.
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The way we currently deal with quota and process accounting that might
keep vfsmount busy at umount time is inherently broken; we try to turn
them off just in case (not quite correctly, at that) and
a) pray umount doesn't fail (otherwise they'll stay turned off)
b) pray nobody doesn anything funny just as we turn quota off
Moreover, LSM provides hooks for doing the same sort of broken logics.
The proper way to deal with that is to introduce the second kind of
reference to vfsmount. Semantics:
- when the last normal reference is dropped, all special ones are
converted to normal ones and if there had been any, cleanup is done.
- normal reference can be cloned into a special one
- special reference can be converted to normal one; that's a no-op if
we'd already passed the point of no return (i.e. mntput() had
converted special references to normal and started cleanup).
The way it works: e.g. starting process accounting converts the vfsmount
reference pinned by the opened file into special one and turns it back
to normal when it gets shut down; acct_auto_close() is done when no
normal references are left. That way it does *not* obstruct umount(2)
and it silently gets turned off when the last normal reference to
vfsmount is gone. Which is exactly what we want...
The same should be done by LSM module that holds some internal
references to vfsmount and wants to shut them down on umount - it should
make them special and security_sb_umount_close() will be called exactly
when the last normal reference to vfsmount is gone.
quota handling is even simpler - we don't use normal file IO anymore, so
there's no need to hold vfsmounts at all. DQUOT_OFF() is done from
deactivate_super(), where it really belongs.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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kernel/power/disk.c needs a declaration of name_to_dev_t() in scope. mount.h
seems like an appropriate choice.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch renames _mntput() to something a little more descriptive:
mntput_no_expire().
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch renames vfsmount->mnt_fslink to something a little more
descriptive: vfsmount->mnt_expire.
Signed-off-by: Mike Waychison <michael.waychison@sun.com>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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<linux/mount.h> uses atomic_t and spinlock_t, but doesn't include either
<asm/atomic.h> or <linux/spinlock.h>, which means that any users of
<linux/mount.h> have to include them. This patch adds the necessary
#includes to avoid this.
Signed-off-by: Roland Dreier <roland@topspin.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Here's a patch that I worked out with Al Viro that adds support for a
filesystem (such as kAFS) to perform automounting intrinsically without the
need for a userspace daemon. It also adds support for such mountpoints to be
degraded at the filesystem's behest until they've been untouched long enough
that they'll be removed.
I've a patch (to follow) that removes some #ifdef's from fs/afs/* thus
allowing it to make use of this facility.
There are five pieces to this:
(1) Any interested filesystem needs to have at least one list to which
expirable mountpoints can be added.
Access to this list is governed by the vfsmount_lock.
(2) When a filesystem wants to create an expirable mount, it calls
do_kern_mount() to get a handle on the filesystem it wants mounting, and
then calls do_add_mount() to mount that filesystem on the designated
mountpoint, supplying the list mentioned in (1) to which the vfsmount
will be added.
In kAFS's case, the mountpoint is a directory with a follow_link() method
defined (fs/afs/mntpt.c). This uses the struct nameidata supplied as an
argument as a determination of where the new filesystem should be
mounted.
(3) When something using a vfsmount finishes dealing with it, it calls
mntput(). This unmarks the vfsmount for immediate expiry.
There are two criteria for determining if a vfsmount may be expired - it
mustn't be marked as in use for anything other than being a child of
another vfsmount, and it must have an expiry mark against it already.
(4) The filesystem then determines the policy on expiring the mounts created
in (2). When it feels the need to, it passes the list mentioned in (1) to
mark_mounts_for_expiry() to request everything on the list be expired.
This function examines each mount listed. If the vfsmount meets the
criteria mentioned in (3), then the vfsmount is deleted from the
namespace and disposed of as for unmounting; otherwise the vfsmount is
left untouched apart from now bearing an expiration mark if it didn't
before.
kAFS's expiration policy is simply to invoke this process at regular
intervals for all the mounts on its list.
(5) An expiration facility is also provided to userspace: by calling umount()
with a MNT_EXPIRE flag, it can make a request to unmount only if the
mountpoint hasn't been used since the last request and isn't in use now.
This allows expiration to be driven by userspace instead of by the
kernel if that is desirable.
This also means that do_umount() has to use a different version of
path_release() to everyone else... it can't call mntput() as that clears
the expiration flag, thus rendering this unachievable; so it's version of
path_release() calls _mntput(), which doesn't do the clear.
My original idea was to give the kernel more knowledge of automounted
things. This avoids a certain problem with stat() on a mountpoint causing it
to mount (for example, do "ls -l /afs" on a machine with kAFS), but Al wanted
it done this way.
> Why is autofs unsuitable?
Because:
(1) Autofs is flat; AFS requires a tree - mounts on mounts on mounts on
mounts...
(2) AFS holds the data as to what the mountpoints are and where they go, and
these may be cross-links to subtrees beyond your control. It's also not
trivial to extract a list of mountpoints as is required for autofs.
(3) Autofs is not namespace safe.
(4) Ducking back to userspace to get that to do the mount is pretty tricky if
namespaces are involved.
In fact, autofs may well want to make use of this facility.
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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From: Maneesh Soni <maneesh@in.ibm.com>
While path walking we do follow_mount or follow_down which uses
dcache_lock for serialisation. vfsmount related operations also use
dcache_lock for all updates. I think we can use a separate lock for
vfsmount related work and can improve path walking.
The following two patches does the same. The first one replaces
dcache_lock with new vfsmount_lock in namespace.c. The lock is
local to namespace.c and is not required outside. The second patch
uses RCU to have lock free lookup_mnt(). The patches are quite simple
and straight forward.
The lockmeter reults show reduced contention, and lock acquisitions
for dcache_lock while running dcachebench* on a 4-way SMP box
SPINLOCKS HOLD WAIT
UTIL CON MEAN( MAX ) MEAN( MAX )(% CPU) TOTAL NOWAIT SPIN RJECT NAME
baselkm-2569:
20.7% 20.9% 0.5us( 146us) 2.9us( 144us)(0.81%) 31590840 79.1% 20.9% 0% dcache_lock
mntlkm-2569:
14.3% 13.6% 0.4us( 170us) 2.9us( 187us)(0.42%) 23071746 86.4% 13.6% 0% dcache_lock
We get more than 8% improvement on 4-way SMP and 44% improvement on 16-way
NUMAQ while runing dcachebench*.
Average (usecs/iteration) Std. Deviation
(lower is better)
4-way SMP
2.5.69 15739.3 470.90
2.5.69-mnt 14459.6 298.51
16-way NUMAQ
2.5.69 120426.5 363.78
2.5.69-mnt 63225.8 427.60
*dcachebench is a microbenchmark written by Bill Hartner and is available at
http://www-124.ibm.com/developerworks/opensource/linuxperf/dcachebench/dcachebench.html
vfsmount_lock.patch
-------------------
- Patch for replacing dcache_lock with new vfsmount_lock for all mount
related operation. This removes the need to take dcache_lock while
doing follow_mount or follow_down operations in path walking.
I re-ran dcachebench with 2.5.70 as base on 16-way NUMAQ box.
Average (usecs/iteration) Std. Deviation
(lower is better)
16-way NUMAQ
2.5.70 120710.9 230.67
+ vfsmount_lock.patch 65209.6 242.97
+ lookup_mnt-rcu.patch 64042.3 416.61
So just the lock splitting (vfsmount_lock.patch) gives almost similar benifits
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(i) The prototypes for free_vfsmnt(), alloc_vfsmnt(), do_kern_mount()
so far occurred in several individual c files. Now they are in
<linux/mount.h>.
(ii) do_kern_mount() has a third argument name that is typically a
constant. It is called with "rootfs", "nfsd", type->name,
"capifs", "usbdevfs", "binfmt_misc" etc. So, it should have a
prototype that expresses this:
do_kern_mount(const char *fstype, int flags, const char *name, void *data);
This makes the ugly cast
- return do_kern_mount(type->name, 0, (char *)type->name, NULL);
+ return do_kern_mount(type->name, 0, type->name, NULL);
go away. Now do_kern_mount() calls type->get_sb(), so also get_sb()
must have a const third argument. That is what the patch below does.
If I am not mistaken, precisely two filesystems do not treat this
argument as a constant, namely afs and cifs. A separate patch
gives some cleanup there.
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- Include dcache.h/namei.h in fs/autofs/autofs_i.h not dirhash.c
- Include list.h and spinlock.h in dcache.h
- Include list.h in mount.h and namei.h
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- Keith Owens: module exporting error checking
- Greg KH: USB update
- Paul Mackerras: clean up wait_init_idle(), ppc prefetch macros
- Jan Kara: quota fixes
- Abraham vd Merwe: agpgart support for Intel 830M
- Jakub Jelinek: ELF loader cleanups
- Al Viro: more cleanups
- David Miller: sparc64 fix, netfilter fixes
- me: tweak resurrected oom handling
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- Greg KH: start migration to new "min()/max()"
- Roman Zippel: move affs over to "min()/max()".
- Vojtech Pavlik: VIA update (make sure not to IRQ-unmask a vt82c576)
- Jan Kara: quota bug-fix (don't decrement quota for non-counted inode)
- Anton Altaparmakov: more NTFS updates
- Al Viro: make nosuid/noexec/nodev be per-mount flags, not per-filesystem
- Alan Cox: merge input/joystick layer differences, driver and alpha merge
- Keith Owens: scsi Makefile cleanup
- Trond Myklebust: fix oopsable race in locking code
- Jean Tourrilhes: IrDA update
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- Jeff Hartmann: serverworks AGP gart unload memory leak fix
- Marcelo Tosatti: make zone_inactive_shortage() return how big the shortage is.
- Hugh Dickins: tidy up age_page_down()
- Al Viro: super block handling cleanups
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- Takanori Kawano: brlock indexing bugfix
- Ingo Molnar, Jeff Garzik: softirq updates and fixes
- Al Viro: rampage of superblock cleanups.
- Jean Tourrilhes: Orinoco driver update v6, IrNET update
- Trond Myklebust: NFS brown-paper-bag thing
- Tim Waugh: parport update
- David Miller: networking and sparc updates
- Jes Sorensen: m68k update.
- Ben Fennema: UDF update
- Geert Uytterhoeven: fbdev logo updates
- Willem Riede: osst driver updates
- Paul Mackerras: PPC update
- Marcelo Tosatti: unlazy swap cache
- Mikulas Patocka: hpfs update
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- Alan Cox: camera conversion missed parts
- Neil Brown: md graceful alloc failure
- Andrea Arkangeli: more alpha fixups, bounce buffer deadlock avoidance
- Adam Fritzler: tms380tr driver update
- Al Viro: VFS layer cleanups
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