1. 15 Jan, 2011 6 commits
    • Ian Kent's avatar
      autofs4: Clean up dentry operations · 71e469db
      Ian Kent authored
      
      
      There are now two distinct dentry operations uses. One for dentrys
      that trigger mounts and one for dentrys that do not.
      
      Rationalize the use of these dentry operations and rename them to
      reflect their function.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      71e469db
    • Ian Kent's avatar
      autofs4: Clean up inode operations · e61da20a
      Ian Kent authored
      
      
      Since the use of ->follow_link() has been eliminated there is no
      need to separate the indirect and direct inode operations.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      e61da20a
    • Ian Kent's avatar
      autofs4: Remove unused code · 8c13a676
      Ian Kent authored
      
      
      Remove code that is not used due to the use of ->d_automount()
      and ->d_manage().
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      8c13a676
    • Ian Kent's avatar
      autofs4: Add d_manage() dentry operation · b5b80177
      Ian Kent authored
      
      
      This patch required a previous patch to add the ->d_automount()
      dentry operation.
      
      Add a function to use the newly defined ->d_manage() dentry operation
      for blocking during mount and expire.
      
      Whether the VFS calls the dentry operations d_automount() and d_manage()
      is controled by the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags. autofs
      uses the d_automount() operation to callback to user space to request
      mount operations and the d_manage() operation to block walks into mounts
      that are under construction or destruction.
      
      In order to prevent these functions from being called unnecessarily the
      DMANAGED_* flags are cleared for cases which would cause this. In the
      common case the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags are both
      set for dentrys waiting to be mounted. The DMANAGED_TRANSIT flag is
      cleared upon successful mount request completion and set during expire
      runs, both during the dentry expire check, and if selected for expire,
      is left set until a subsequent successful mount request completes.
      
      The exception to this is the so-called rootless multi-mount which has
      no actual mount at its base. In this case the DMANAGED_AUTOMOUNT flag
      is cleared upon successful mount request completion as well and set
      again after a successful expire.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      b5b80177
    • Ian Kent's avatar
      autofs4: Add d_automount() dentry operation · 10584211
      Ian Kent authored
      
      
      Add a function to use the newly defined ->d_automount() dentry operation
      for triggering mounts instead of doing the user space callback in ->lookup()
      and ->d_revalidate().
      
      Note, to be useful the subsequent patch to add the ->d_manage() dentry
      operation is also needed so the discussion of functionality is deferred to
      that patch.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      10584211
    • David Howells's avatar
      Add a dentry op to allow processes to be held during pathwalk transit · cc53ce53
      David Howells authored
      
      
      Add a dentry op (d_manage) to permit a filesystem to hold a process and make it
      sleep when it tries to transit away from one of that filesystem's directories
      during a pathwalk.  The operation is keyed off a new dentry flag
      (DCACHE_MANAGE_TRANSIT).
      
      The filesystem is allowed to be selective about which processes it holds and
      which it permits to continue on or prohibits from transiting from each flagged
      directory.  This will allow autofs to hold up client processes whilst letting
      its userspace daemon through to maintain the directory or the stuff behind it
      or mounted upon it.
      
      The ->d_manage() dentry operation:
      
      	int (*d_manage)(struct path *path, bool mounting_here);
      
      takes a pointer to the directory about to be transited away from and a flag
      indicating whether the transit is undertaken by do_add_mount() or
      do_move_mount() skipping through a pile of filesystems mounted on a mountpoint.
      
      It should return 0 if successful and to let the process continue on its way;
      -EISDIR to prohibit the caller from skipping to overmounted filesystems or
      automounting, and to use this directory; or some other error code to return to
      the user.
      
      ->d_manage() is called with namespace_sem writelocked if mounting_here is true
      and no other locks held, so it may sleep.  However, if mounting_here is true,
      it may not initiate or wait for a mount or unmount upon the parameter
      directory, even if the act is actually performed by userspace.
      
      Within fs/namei.c, follow_managed() is extended to check with d_manage() first
      on each managed directory, before transiting away from it or attempting to
      automount upon it.
      
      follow_down() is renamed follow_down_one() and should only be used where the
      filesystem deliberately intends to avoid management steps (e.g. autofs).
      
      A new follow_down() is added that incorporates the loop done by all other
      callers of follow_down() (do_add/move_mount(), autofs and NFSD; whilst AFS, NFS
      and CIFS do use it, their use is removed by converting them to use
      d_automount()).  The new follow_down() calls d_manage() as appropriate.  It
      also takes an extra parameter to indicate if it is being called from mount code
      (with namespace_sem writelocked) which it passes to d_manage().  follow_down()
      ignores automount points so that it can be used to mount on them.
      
      __follow_mount_rcu() is made to abort rcu-walk mode if it hits a directory with
      DCACHE_MANAGE_TRANSIT set on the basis that we're probably going to have to
      sleep.  It would be possible to enter d_manage() in rcu-walk mode too, and have
      that determine whether to abort or not itself.  That would allow the autofs
      daemon to continue on in rcu-walk mode.
      
      Note that DCACHE_MANAGE_TRANSIT on a directory should be cleared when it isn't
      required as every tranist from that directory will cause d_manage() to be
      invoked.  It can always be set again when necessary.
      
      ==========================
      WHAT THIS MEANS FOR AUTOFS
      ==========================
      
      Autofs currently uses the lookup() inode op and the d_revalidate() dentry op to
      trigger the automounting of indirect mounts, and both of these can be called
      with i_mutex held.
      
      autofs knows that the i_mutex will be held by the caller in lookup(), and so
      can drop it before invoking the daemon - but this isn't so for d_revalidate(),
      since the lock is only held on _some_ of the code paths that call it.  This
      means that autofs can't risk dropping i_mutex from its d_revalidate() function
      before it calls the daemon.
      
      The bug could manifest itself as, for example, a process that's trying to
      validate an automount dentry that gets made to wait because that dentry is
      expired and needs cleaning up:
      
      	mkdir         S ffffffff8014e05a     0 32580  24956
      	Call Trace:
      	 [<ffffffff885371fd>] :autofs4:autofs4_wait+0x674/0x897
      	 [<ffffffff80127f7d>] avc_has_perm+0x46/0x58
      	 [<ffffffff8009fdcf>] autoremove_wake_function+0x0/0x2e
      	 [<ffffffff88537be6>] :autofs4:autofs4_expire_wait+0x41/0x6b
      	 [<ffffffff88535cfc>] :autofs4:autofs4_revalidate+0x91/0x149
      	 [<ffffffff80036d96>] __lookup_hash+0xa0/0x12f
      	 [<ffffffff80057a2f>] lookup_create+0x46/0x80
      	 [<ffffffff800e6e31>] sys_mkdirat+0x56/0xe4
      
      versus the automount daemon which wants to remove that dentry, but can't
      because the normal process is holding the i_mutex lock:
      
      	automount     D ffffffff8014e05a     0 32581      1              32561
      	Call Trace:
      	 [<ffffffff80063c3f>] __mutex_lock_slowpath+0x60/0x9b
      	 [<ffffffff8000ccf1>] do_path_lookup+0x2ca/0x2f1
      	 [<ffffffff80063c89>] .text.lock.mutex+0xf/0x14
      	 [<ffffffff800e6d55>] do_rmdir+0x77/0xde
      	 [<ffffffff8005d229>] tracesys+0x71/0xe0
      	 [<ffffffff8005d28d>] tracesys+0xd5/0xe0
      
      which means that the system is deadlocked.
      
      This patch allows autofs to hold up normal processes whilst the daemon goes
      ahead and does things to the dentry tree behind the automouter point without
      risking a deadlock as almost no locks are held in d_manage() and none in
      d_automount().
      
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Was-Acked-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      cc53ce53
  2. 06 Jan, 2011 3 commits
    • Nick Piggin's avatar
      fs: dcache remove dcache_lock · b5c84bf6
      Nick Piggin authored
      
      
      dcache_lock no longer protects anything. remove it.
      
      Signed-off-by: default avatarNick Piggin <npiggin@kernel.dk>
      b5c84bf6
    • Nick Piggin's avatar
      fs: dcache scale subdirs · 2fd6b7f5
      Nick Piggin authored
      
      
      Protect d_subdirs and d_child with d_lock, except in filesystems that aren't
      using dcache_lock for these anyway (eg. using i_mutex).
      
      Note: if we change the locking rule in future so that ->d_child protection is
      provided only with ->d_parent->d_lock, it may allow us to reduce some locking.
      But it would be an exception to an otherwise regular locking scheme, so we'd
      have to see some good results. Probably not worthwhile.
      
      Signed-off-by: default avatarNick Piggin <npiggin@kernel.dk>
      2fd6b7f5
    • Nick Piggin's avatar
      fs: dcache scale d_unhashed · da502956
      Nick Piggin authored
      
      
      Protect d_unhashed(dentry) condition with d_lock. This means keeping
      DCACHE_UNHASHED bit in synch with hash manipulations.
      
      Signed-off-by: default avatarNick Piggin <npiggin@kernel.dk>
      da502956
  3. 03 Mar, 2010 1 commit
  4. 16 Dec, 2009 4 commits
  5. 11 Jun, 2009 1 commit
  6. 01 Apr, 2009 1 commit
  7. 06 Jan, 2009 1 commit
    • Ian Kent's avatar
      autofs4: make autofs type usage explicit · a92daf6b
      Ian Kent authored
      
      
      - the type assigned at mount when no type is given is changed
        from 0 to AUTOFS_TYPE_INDIRECT. This was done because 0 and
        AUTOFS_TYPE_INDIRECT were being treated implicitly as the same
        type.
      
      - previously, an offset mount had it's type set to
        AUTOFS_TYPE_DIRECT|AUTOFS_TYPE_OFFSET but the mount control
        re-implementation needs to be able distinguish all three types.
        So this was changed to make the type setting explicit.
      
      - a type AUTOFS_TYPE_ANY was added for use by the re-implementation
        when checking if a given path is a mountpoint. It's not really a
        type as we use this to ask if a given path is a mountpoint in the
        autofs_dev_ioctl_ismountpoint() function.
      
      - functions to set and test the autofs mount types have been added to
        improve readability and make the type usage explicit.
      
      - the mount type is used from user space for the mount control
        re-implementtion so, for consistency, all the definitions have
        been moved to the user space include file include/linux/auto_fs4.h.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarJeff Moyer <jmoyer@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a92daf6b
  8. 16 Oct, 2008 3 commits
  9. 24 Jul, 2008 7 commits
    • Ian Kent's avatar
      autofs4: reorganize expire pending wait function calls · 06a35985
      Ian Kent authored
      
      
      This patch re-orgnirzes the checking for and waiting on active expires and
      elininates redundant checks.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Cc: Jeff Moyer <jmoyer@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      06a35985
    • Ian Kent's avatar
      autofs4: fix direct mount pending expire race · 6e60a9ab
      Ian Kent authored
      
      
      For direct and offset type mounts that are covered by another mount we
      cannot check the AUTOFS_INF_EXPIRING flag during a path walk which leads
      to lookups walking into an expiring mount while it is being expired.
      
      For example, for the direct multi-mount map entry with a couple of
      offsets:
      
      /race/mm1  /      <server1>:/<path1>
                 /om1   <server2>:/<path2>
                 /om2   <server1>:/<path3>
      
      an autofs trigger mount is mounted on /race/mm1 and when accessed it is
      over mounted and trigger mounts made for /race/mm1/om1 and /race/mm1/om2.
      So it isn't possible for path walks to see the expiring flag at all and
      they happily walk into the file system while it is expiring.
      
      When expiring these mounts follow_down() must stop at the autofs mount and
      all processes must block in the ->follow_link() method (except the daemon)
      until the expire is complete.  This is done by decrementing the d_mounted
      field of the autofs trigger mount root dentry until the expire is
      completed.  In ->follow_link() all processes wait on the expire and the
      mount following is completed for the daemon until the expire is complete.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Cc: Jeff Moyer <jmoyer@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6e60a9ab
    • Ian Kent's avatar
      autofs4: fix indirect mount pending expire race · 97e7449a
      Ian Kent authored
      
      
      The selection of a dentry for expiration and the setting of the
      AUTOFS_INF_EXPIRING flag isn't done atomically which can lead to lookups
      walking into an expiring mount.
      
      What happens is that an expire is initiated by the daemon and a dentry is
      selected for expire but, since there is no lock held between the selection
      and setting of the expiring flag, a process may find the flag clear and
      continue walking into the mount tree at the same time the daemon attempts
      the expire it.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Reviewed-by: default avatarJeff Moyer <jmoyer@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      97e7449a
    • Ian Kent's avatar
      autofs4: fix waitq memory leak · 296f7bf7
      Ian Kent authored
      
      
      If an autofs mount becomes catatonic before autofs4_wait_release() is
      called the wait queue counter will not be decremented down to zero and the
      entry will never be freed.  There are also races decrementing the wait
      counter in the wait release function.  To deal with this the counter needs
      to be updated while holding the wait queue mutex and waiters need to be
      woken up unconditionally when the wait is removed from the queue to ensure
      we eventually free the wait.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      296f7bf7
    • Jeff Moyer's avatar
      autofs4: use struct qstr in waitq.c · 70b52a0a
      Jeff Moyer authored
      
      
      The autofs_wait_queue already contains all of the fields of the
      struct qstr, so change it into a qstr.
      
      This patch, from Jeff Moyer, has been modified a liitle by myself.
      
      Signed-off-by: default avatarJeff Moyer <jmoyer@redhat.com>
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      70b52a0a
    • Ian Kent's avatar
      autofs4: use look aside list for lookups · 25767378
      Ian Kent authored
      
      
      A while ago a patch to resolve a deadlock during directory creation was
      merged.  This delayed the hashing of lookup dentrys until the ->mkdir()
      (or ->symlink()) operation completed to ensure we always went through
      ->lookup() instead of also having processes go through ->revalidate() so
      our VFS locking remained consistent.
      
      Now we are seeing a couple of side affects of that change in situations
      with heavy mount activity.
      
      Two cases have been identified:
      
      1) When a mount request is triggered, due to the delayed hashing, the
         directory created by user space for the mount point doesn't have the
         DCACHE_AUTOFS_PENDING flag set.  In the case of an autofs multi-mount
         where a tree of mount point directories are created this can lead to
         the path walk continuing rather than the dentry being sent to the wait
         queue to wait for request completion.  This is because, if the pending
         flag isn't set, the criteria for deciding this is a mount in progress
         fails to hold, namely that the dentry is not a mount point and has no
         subdirectories.
      
      2) A mount request dentry is initially created negative and unhashed.
         It remains this way until the ->mkdir() callback completes.  Since it
         is unhashed a fresh dentry is used when the user space mount request
         creates the mount point directory.  This leaves the original dentry
         negative and unhashed.  But revalidate has no way to tell the VFS that
         the dentry has changed, other than to force another ->lookup() by
         returning false, which is at best wastefull and at worst not possible.
         This results in an -ENOENT return from the original path walk when in
         fact the mount succeeded.
      
      To resolve this we need to ensure that the same dentry is used in all
      calls to ->lookup() during the course of a mount request.  This patch
      achieves that by adding the initial dentry to a look aside list and
      removes it at ->mkdir() or ->symlink() completion (or when the dentry is
      released), since these are the only create operations autofs4 supports.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      25767378
    • Ian Kent's avatar
      autofs4: don't make expiring dentry negative · 5f6f4f28
      Ian Kent authored
      
      
      Correct the error of making a positive dentry negative after it has been
      instantiated.
      
      The code that makes this error attempts to re-use the dentry from a
      concurrent expire and mount to resolve a race and the dentry used for the
      lookup must be negative for mounts to trigger in the required cases.  The
      fact is that the dentry doesn't need to be re-used because all that is
      needed is to preserve the flag that indicates an expire is still
      incomplete at the time of the mount request.
      
      This change uses the the dentry to check the flag and wait for the expire
      to complete then discards it instead of attempting to re-use it.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      5f6f4f28
  10. 30 Apr, 2008 1 commit
  11. 19 Oct, 2007 1 commit
    • Pavel Emelianov's avatar
      pid namespaces: round up the API · a47afb0f
      Pavel Emelianov authored
      
      
      The set of functions process_session, task_session, process_group and
      task_pgrp is confusing, as the names can be mixed with each other when looking
      at the code for a long time.
      
      The proposals are to
      * equip the functions that return the integer with _nr suffix to
        represent that fact,
      * and to make all functions work with task (not process) by making
        the common prefix of the same name.
      
      For monotony the routines signal_session() and set_signal_session() are
      replaced with task_session_nr() and set_task_session(), especially since they
      are only used with the explicit task->signal dereference.
      
      Signed-off-by: default avatarPavel Emelianov <xemul@openvz.org>
      Acked-by: default avatarSerge E. Hallyn <serue@us.ibm.com>
      Cc: Kirill Korotaev <dev@openvz.org>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Cedric Le Goater <clg@fr.ibm.com>
      Cc: Herbert Poetzl <herbert@13thfloor.at>
      Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a47afb0f
  12. 20 Feb, 2007 1 commit
    • Ian Kent's avatar
      [PATCH] autofs4: fix another race between mount and expire · f50b6f86
      Ian Kent authored
      
      
      Jeff Moyer has identified a race between mount and expire.
      
      What happens is that during an expire the situation can arise that a directory
      is removed and another lookup is done before the expire issues a completion
      status to the kernel module.  In this case, since the the lookup gets a new
      dentry, it doesn't know that there is an expire in progress and when it posts
      its mount request, matches the existing expire request and waits for its
      completion.  ENOENT is then returned to user space from lookup (as the dentry
      passed in is now unhashed) without having performed the mount request.
      
      The solution used here is to keep track of dentrys in this unhashed state and
      reuse them, if possible, in order to preserve the flags.  Additionally, this
      infrastructure will provide the framework for the reintroduction of caching of
      mount fails removed earlier in development.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Acked-by: default avatarJeff Moyer <jmoyer@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      f50b6f86
  13. 12 Feb, 2007 1 commit
  14. 08 Dec, 2006 1 commit
  15. 11 Oct, 2006 1 commit
  16. 24 Sep, 2006 1 commit
  17. 15 May, 2006 1 commit
    • Ian Kent's avatar
      [PATCH] autofs4: NFY_NONE wait race fix · a5370553
      Ian Kent authored
      
      
      This patch fixes two problems.
      
      First, the comparison of entries in the waitq.c was incorrect.
      
      Second, the NFY_NONE check was incorrect. The test of whether the dentry
      is mounted if ineffective, for example, if an expire fails then we could
      wait forever on a non existant expire. The bug was identified by Jeff
      Moyer.
      
      The patch changes autofs4 to wait on expires only as this is all that's
      needed.  If there is no existing wait when autofs4_wait is call with a type
      of NFY_NONE it delays until either a wait appears or the the expire flag is
      cleared.
      
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      a5370553
  18. 28 Mar, 2006 2 commits
  19. 27 Mar, 2006 3 commits