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* smarter propagate_mnt()Al Viro2014-04-021-79/+119
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The current mainline has copies propagated to *all* nodes, then tears down the copies we made for nodes that do not contain counterparts of the desired mountpoint. That sets the right propagation graph for the copies (at teardown time we move the slaves of removed node to a surviving peer or directly to master), but we end up paying a fairly steep price in useless allocations. It's fairly easy to create a situation where N calls of mount(2) create exactly N bindings, with O(N^2) vfsmounts allocated and freed in process. Fortunately, it is possible to avoid those allocations/freeings. The trick is to create copies in the right order and find which one would've eventually become a master with the current algorithm. It turns out to be possible in O(nodes getting propagation) time and with no extra allocations at all. One part is that we need to make sure that eventual master will be created before its slaves, so we need to walk the propagation tree in a different order - by peer groups. And iterate through the peers before dealing with the next group. Another thing is finding the (earlier) copy that will be a master of one we are about to create; to do that we are (temporary) marking the masters of mountpoints we are attaching the copies to. Either we are in a peer of the last mountpoint we'd dealt with, or we have the following situation: we are attaching to mountpoint M, the last copy S_0 had been attached to M_0 and there are sequences S_0...S_n, M_0...M_n such that S_{i+1} is a master of S_{i}, S_{i} mounted on M{i} and we need to create a slave of the first S_{k} such that M is getting propagation from M_{k}. It means that the master of M_{k} will be among the sequence of masters of M. On the other hand, the nearest marked node in that sequence will either be the master of M_{k} or the master of M_{k-1} (the latter - in the case if M_{k-1} is a slave of something M gets propagation from, but in a wrong peer group). So we go through the sequence of masters of M until we find a marked one (P). Let N be the one before it. Then we go through the sequence of masters of S_0 until we find one (say, S) mounted on a node D that has P as master and check if D is a peer of N. If it is, S will be the master of new copy, if not - the master of S will be. That's it for the hard part; the rest is fairly simple. Iterator is in next_group(), handling of one prospective mountpoint is propagate_one(). It seems to survive all tests and gives a noticably better performance than the current mainline for setups that are seriously using shared subtrees. Cc: stable@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* switch mnt_hash to hlistAl Viro2014-03-311-11/+15
| | | | | | | | | | | | | fixes RCU bug - walking through hlist is safe in face of element moves, since it's self-terminating. Cyclic lists are not - if we end up jumping to another hash chain, we'll loop infinitely without ever hitting the original list head. [fix for dumb braino folded] Spotted by: Max Kellermann <mk@cm4all.com> Cc: stable@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* split __lookup_mnt() in two functionsAl Viro2013-10-251-3/+3
| | | | | | | | Instead of passing the direction as argument (and checking it on every step through the hash chain), just have separate __lookup_mnt() and __lookup_mnt_last(). And use the standard iterators... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* new helpers: lock_mount_hash/unlock_mount_hashAl Viro2013-10-251-2/+2
| | | | | | | aka br_write_{lock,unlock} of vfsmount_lock. Inlines in fs/mount.h, vfsmount_lock extern moved over there as well. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* namespace.c: get rid of mnt_ghostsAl Viro2013-10-251-2/+1
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: Fix invalid ida_remove() callTakashi Iwai2013-05-311-1/+2
| | | | | | | | | | | | | When the group id of a shared mount is not allocated, the umount still tries to call mnt_release_group_id(), which eventually hits a kernel warning at ida_remove() spewing a message like: ida_remove called for id=0 which is not allocated. This patch fixes the bug simply checking the group id in the caller. Reported-by: Cristian Rodríguez <crrodriguez@opensuse.org> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Merge branch 'for-linus' of ↵Linus Torvalds2013-05-021-6/+4
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull VFS updates from Al Viro, Misc cleanups all over the place, mainly wrt /proc interfaces (switch create_proc_entry to proc_create(), get rid of the deprecated create_proc_read_entry() in favor of using proc_create_data() and seq_file etc). 7kloc removed. * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (204 commits) don't bother with deferred freeing of fdtables proc: Move non-public stuff from linux/proc_fs.h to fs/proc/internal.h proc: Make the PROC_I() and PDE() macros internal to procfs proc: Supply a function to remove a proc entry by PDE take cgroup_open() and cpuset_open() to fs/proc/base.c ppc: Clean up scanlog ppc: Clean up rtas_flash driver somewhat hostap: proc: Use remove_proc_subtree() drm: proc: Use remove_proc_subtree() drm: proc: Use minor->index to label things, not PDE->name drm: Constify drm_proc_list[] zoran: Don't print proc_dir_entry data in debug reiserfs: Don't access the proc_dir_entry in r_open(), r_start() r_show() proc: Supply an accessor for getting the data from a PDE's parent airo: Use remove_proc_subtree() rtl8192u: Don't need to save device proc dir PDE rtl8187se: Use a dir under /proc/net/r8180/ proc: Add proc_mkdir_data() proc: Move some bits from linux/proc_fs.h to linux/{of.h,signal.h,tty.h} proc: Move PDE_NET() to fs/proc/proc_net.c ...
| * switch unlock_mount() to namespace_unlock(), convert all umount_tree() callersAl Viro2013-04-091-3/+1
| | | | | | | | | | | | | | which allows to kill the last argument of umount_tree() and make release_mounts() static. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
| * get rid of full-hash scan on detaching vfsmountsAl Viro2013-04-091-3/+3
| | | | | | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* | vfs: Carefully propogate mounts across user namespacesEric W. Biederman2013-03-271-0/+6
|/ | | | | | | | | | | | | | | | | | | | | As a matter of policy MNT_READONLY should not be changable if the original mounter had more privileges than creator of the mount namespace. Add the flag CL_UNPRIVILEGED to note when we are copying a mount from a mount namespace that requires more privileges to a mount namespace that requires fewer privileges. When the CL_UNPRIVILEGED flag is set cause clone_mnt to set MNT_NO_REMOUNT if any of the mnt flags that should never be changed are set. This protects both mount propagation and the initial creation of a less privileged mount namespace. Cc: stable@vger.kernel.org Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Reported-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
* VFS: Make clone_mnt()/copy_tree()/collect_mounts() return errorsDavid Howells2012-07-141-2/+3
| | | | | | | | | | | | | | | | | | copy_tree() can theoretically fail in a case other than ENOMEM, but always returns NULL which is interpreted by callers as -ENOMEM. Change it to return an explicit error. Also change clone_mnt() for consistency and because union mounts will add new error cases. Thanks to Andreas Gruenbacher <agruen@suse.de> for a bug fix. [AV: folded braino fix by Dan Carpenter] Original-author: Valerie Aurora <vaurora@redhat.com> Signed-off-by: David Howells <dhowells@redhat.com> Cc: Valerie Aurora <valerie.aurora@gmail.com> Cc: Andreas Gruenbacher <agruen@suse.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* brlocks/lglocks: API cleanupsAndi Kleen2012-05-301-2/+2
| | | | | | | | | | | | | | | | | | | | | lglocks and brlocks are currently generated with some complicated macros in lglock.h. But there's no reason to not just use common utility functions and put all the data into a common data structure. In preparation, this patch changes the API to look more like normal function calls with pointers, not magic macros. The patch is rather large because I move over all users in one go to keep it bisectable. This impacts the VFS somewhat in terms of lines changed. But no actual behaviour change. [akpm@linux-foundation.org: checkpatch fixes] Signed-off-by: Andi Kleen <ak@linux.intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: switch pnode.h macros to struct mount *Al Viro2012-01-041-3/+3
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: move the rest of int fields to struct mountAl Viro2012-01-041-1/+1
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: mnt_id/mnt_group_id movedAl Viro2012-01-041-2/+2
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: mnt_ns moved to struct mountAl Viro2012-01-041-5/+5
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: take mnt_share/mnt_slave/mnt_slave_list and mnt_expire to struct mountAl Viro2012-01-041-15/+15
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: and now we can make ->mnt_master point to struct mountAl Viro2012-01-041-9/+9
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: take mnt_master to struct mountAl Viro2012-01-041-13/+13
| | | | | | make IS_MNT_SLAVE take struct mount * at the same time Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - remaining argument of mnt_set_mountpoint()Al Viro2012-01-041-1/+1
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - propagate_mnt()Al Viro2012-01-041-6/+6
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - shared subtree iteratorsAl Viro2012-01-041-50/+47
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - get_dominating_id / do_make_slaveAl Viro2012-01-041-29/+29
| | | | | | | next pile of horrors, similar to mnt_parent one; this time it's mnt_master. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: take mnt_child/mnt_mounts to struct mountAl Viro2012-01-041-3/+3
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - work with countersAl Viro2012-01-041-1/+1
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: move mnt_mountpoint to struct mountAl Viro2012-01-041-2/+2
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: now it can be done - make mnt_parent point to struct mountAl Viro2012-01-041-8/+8
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: mnt_parent moved to struct mountAl Viro2012-01-041-2/+2
| | | | | | the second victim... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - is_path_reachableAl Viro2012-01-041-5/+5
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - do_umount/propagate_mount_busyAl Viro2012-01-041-8/+8
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount mnt_set_mountpoint child argumentAl Viro2012-01-041-1/+1
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - clone_mnt/copy_tree argumentAl Viro2012-01-041-1/+1
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - umount_tree argumentAl Viro2012-01-041-1/+1
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: the first spoils - mnt_hash movedAl Viro2012-01-041-5/+5
| | | | | | taken out of struct vfsmount into struct mount Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - clone_mnt/copy_tree resultAl Viro2012-01-041-7/+8
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - change_mnt_propagation/set_mnt_sharedAl Viro2012-01-041-6/+6
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - mount group id handlingAl Viro2012-01-041-1/+1
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - __propagate_umount() argumentAl Viro2012-01-041-7/+7
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: spread struct mount - __lookup_mnt() resultAl Viro2012-01-041-6/+7
| | | | | | switch __lookup_mnt() to returning struct mount *; callers adjusted. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: more mnt_parent cleanupsAl Viro2012-01-041-15/+0
| | | | | | | | | | | | a) mount --move is checking that ->mnt_parent is non-NULL before looking if that parent happens to be shared; ->mnt_parent is never NULL and it's not even an misspelled !mnt_has_parent() b) pivot_root open-codes is_path_reachable(), poorly. c) so does path_is_under(), while we are at it. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* vfs: new internal helper: mnt_has_parent(mnt)Al Viro2012-01-041-1/+1
| | | | | | | | | | | | vfsmounts have ->mnt_parent pointing either to a different vfsmount or to itself; it's never NULL and termination condition in loops traversing the tree towards root is mnt == mnt->mnt_parent. At least one place (see the next patch) is confused about what's going on; let's add an explicit helper checking it right way and use it in all places where we need it. Not that there had been too many, but... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* fs: scale mntget/mntputNick Piggin2011-01-071-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The problem that this patch aims to fix is vfsmount refcounting scalability. We need to take a reference on the vfsmount for every successful path lookup, which often go to the same mount point. The fundamental difficulty is that a "simple" reference count can never be made scalable, because any time a reference is dropped, we must check whether that was the last reference. To do that requires communication with all other CPUs that may have taken a reference count. We can make refcounts more scalable in a couple of ways, involving keeping distributed counters, and checking for the global-zero condition less frequently. - check the global sum once every interval (this will delay zero detection for some interval, so it's probably a showstopper for vfsmounts). - keep a local count and only taking the global sum when local reaches 0 (this is difficult for vfsmounts, because we can't hold preempt off for the life of a reference, so a counter would need to be per-thread or tied strongly to a particular CPU which requires more locking). - keep a local difference of increments and decrements, which allows us to sum the total difference and hence find the refcount when summing all CPUs. Then, keep a single integer "long" refcount for slow and long lasting references, and only take the global sum of local counters when the long refcount is 0. This last scheme is what I implemented here. Attached mounts and process root and working directory references are "long" references, and everything else is a short reference. This allows scalable vfsmount references during path walking over mounted subtrees and unattached (lazy umounted) mounts with processes still running in them. This results in one fewer atomic op in the fastpath: mntget is now just a per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock and non-atomic decrement in the common case. However code is otherwise bigger and heavier, so single threaded performance is basically a wash. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: brlock vfsmount_lockNick Piggin2010-08-181-2/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | 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: Nick Piggin <npiggin@kernel.dk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Kill CL_PROPAGATION, sanitize fs/pnode.c:get_source()Al Viro2010-03-031-11/+17
| | | | | | | | | | | | | | | | First of all, get_source() never results in CL_PROPAGATION alone. We either get CL_MAKE_SHARED (for the continuation of peer group) or CL_SLAVE (slave that is not shared) or both (beginning of peer group among slaves). Massage the code to make that explicit, kill CL_PROPAGATION test in clone_mnt() (nothing sets CL_MAKE_SHARED without CL_PROPAGATION and in clone_mnt() we are checking CL_PROPAGATION after we'd found that there's no CL_SLAVE, so the check for CL_MAKE_SHARED would do just as well). Fix comments, while we are at it... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [patch 7/7] vfs: mountinfo: show dominating group idMiklos Szeredi2008-04-231-0/+51
| | | | | | | | Show peer group ID of nearest dominating group that has intersection with the mount's namespace. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [patch 4/7] vfs: mountinfo: add mount peer group IDMiklos Szeredi2008-04-231-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | 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>
* [PATCH] umount_tree() will unhash everything itselfAl Viro2008-04-221-2/+1
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] move a bunch of declarations to fs/internal.hAl Viro2008-04-221-0/+1
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] count ghost references to vfsmountsAl Viro2008-03-281-1/+1
| | | | | | | | 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>
* MNT_UNBINDABLE fixAndries E. Brouwer2008-02-061-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Some time ago ( http://lkml.org/lkml/2007/6/19/128 ) I wrote about MNT_UNBINDABLE that it felt like a bug that it is not reset by "mount --make-private". Today I happened to see mount(8) and Documentation/sharedsubtree.txt and both document the version obtained by applying the little patch given in the above (and again below). So, the present kernel code is not according to specs and must be regarded as buggy. Specification in Documentation/sharedsubtree.txt: See state diagram: unbindable should become private upon make-private. Specification in mount(8): ... It's also possible to set up uni-directional propagation (with --make- slave), to make a mount point unavailable for --bind/--rbind (with --make-unbindable), and to undo any of these (with --make-private). Repeat of old fix-shared-subtrees-make-private.patch (due to Dirk Gerrits, René Gabriëls, Peter Kooijmans): Acked-by: Ram Pai <linuxram@us.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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