1. 12 Feb, 2011 3 commits
    • Joe Eykholt's avatar
      [SCSI] libfc: add method for setting handler for incoming exchange · 1a5c2d7e
      Joe Eykholt authored
      Add a method for setting handler for incoming exchange.
      For multi-sequence exchanges, this allows the target driver
      to add a response handler for handling subsequent sequences,
      and exchange manager resets.
      
      The new function is called fc_seq_set_resp().
      Signed-off-by: default avatarJoe Eykholt <jeykholt@cisco.com>
      Signed-off-by: default avatarRobert Love <robert.w.love@intel.com>
      Signed-off-by: default avatarJames Bottomley <James.Bottomley@suse.de>
      1a5c2d7e
    • Joe Eykholt's avatar
      [SCSI] libfc: add hook for FC-4 provider registration · 96ad8464
      Joe Eykholt authored
      Allow FC-4 provider modules to hook into libfc, mostly for targets.
      This should allow any FC-4 module to handle PRLI requests and maintain
      process-association states.
      
      Each provider registers its ops with libfc and then will be called for
      any incoming PRLI for that FC-4 type on any instance.   The provider
      can decide whether to handle that particular instance using any method
      it likes, such as ACLs or other configuration information.
      
      A count is kept of the number of successful PRLIs from the remote port.
      Providers are called back with an implicit PRLO when the remote port
      is about to be deleted or has been reset.
      
      fc_lport_recv_req() now sends incoming FC-4 requests to FC-4 providers,
      and there is a built-in provider always registered for handling
      incoming ELS requests.
      
      The call to provider recv() routines uses rcu_read_lock()
      so that providers aren't removed during the call.  That lock is very
      cheap and shouldn't affect any performance on ELS requests.
      Providers can rely on the RCU lock to protect a session lookup as well.
      Signed-off-by: default avatarJoe Eykholt <jeykholt@cisco.com>
      Signed-off-by: default avatarRobert Love <robert.w.love@intel.com>
      Signed-off-by: default avatarJames Bottomley <James.Bottomley@suse.de>
      96ad8464
    • Hannes Reinecke's avatar
      [SCSI] Add detailed SCSI I/O errors · 63583cca
      Hannes Reinecke authored
      Instead of just passing 'EIO' for any I/O error we should be
      notifying the upper layers with more details about the cause
      of this error.
      
      Update the possible I/O errors to:
      
      - ENOLINK: Link failure between host and target
      - EIO: Retryable I/O error
      - EREMOTEIO: Non-retryable I/O error
      - EBADE: I/O error restricted to the I_T_L nexus
      
      'Retryable' in this context means that an I/O error _might_ be
      restricted to the I_T_L nexus (vulgo: path), so retrying on another
      nexus / path might succeed.
      
      'Non-retryable' in general refers to a target failure, so this
      error will always be generated regardless of the I_T_L nexus
      it was send on.
      
      I/O errors restricted to the I_T_L nexus might be retried
      on another nexus / path, but they should _not_ be queued
      if no paths are available.
      Signed-off-by: default avatarHannes Reinecke <hare@suse.de>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      Signed-off-by: default avatarJames Bottomley <James.Bottomley@suse.de>
      63583cca
  2. 24 Jan, 2011 1 commit
  3. 23 Jan, 2011 5 commits
    • Rusty Russell's avatar
      Remove MAYBE_BUILD_BUG_ON · 1765e3a4
      Rusty Russell authored
      Now BUILD_BUG_ON() can handle optimizable constants, we don't need
      MAYBE_BUILD_BUG_ON any more.
      Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      1765e3a4
    • Rusty Russell's avatar
      BUILD_BUG_ON: make it handle more cases · 7ef88ad5
      Rusty Russell authored
      BUILD_BUG_ON used to use the optimizer to do code elimination or fail
      at link time; it was changed to first the size of a negative array (a
      nicer compile time error), then (in
      8c87df45) to a bitfield.
      
      This forced us to change some non-constant cases to MAYBE_BUILD_BUG_ON();
      as Jan points out in that commit, it didn't work as intended anyway.
      
      bitfields: needs a literal constant at parse time, and can't be put under
      	"if (__builtin_constant_p(x))" for example.
      negative array: can handle anything, but if the compiler can't tell it's
      	a constant, silently has no effect.
      link time: breaks link if the compiler can't determine the value, but the
      	linker output is not usually as informative as a compiler error.
      
      If we use the negative-array-size method *and* the link time trick,
      we get the ability to use BUILD_BUG_ON() under __builtin_constant_p()
      branches, and maximal ability for the compiler to detect errors at
      build time.
      
      We also document it thoroughly.
      Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      Cc: Jan Beulich <JBeulich@novell.com>
      Acked-by: default avatarHollis Blanchard <hollisb@us.ibm.com>
      7ef88ad5
    • Linus Walleij's avatar
      param: add null statement to compiled-in module params · b75be420
      Linus Walleij authored
      Add an unused struct declaration statement requiring a
      terminating semicolon to the compile-in case to provoke an
      error if __MODULE_INFO() is used without the terminating
      semicolon. Previously MODULE_ALIAS("foo") (no semicolon)
      compiled fine if MODULE was not selected.
      
      Cc: Dan Carpenter <error27@gmail.com>
      Signed-off-by: default avatarLinus Walleij <linus.walleij@stericsson.com>
      Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      b75be420
    • Rusty Russell's avatar
      module: fix linker error for MODULE_VERSION when !MODULE and CONFIG_SYSFS=n · 3b90a5b2
      Rusty Russell authored
      lib/built-in.o:(__modver+0x8): undefined reference to `__modver_version_show'
      lib/built-in.o:(__modver+0x2c): undefined reference to `__modver_version_show'
      
      Simplest to just not emit anything: if they've disabled SYSFS they probably
      want the smallest kernel possible.
      Reported-by: default avatarRandy Dunlap <randy.dunlap@oracle.com>
      Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      3b90a5b2
    • Dmitry Torokhov's avatar
      module: show version information for built-in modules in sysfs · e94965ed
      Dmitry Torokhov authored
      Currently only drivers that are built as modules have their versions
      shown in /sys/module/<module_name>/version, but this information might
      also be useful for built-in drivers as well. This especially important
      for drivers that do not define any parameters - such drivers, if
      built-in, are completely invisible from userspace.
      
      This patch changes MODULE_VERSION() macro so that in case when we are
      compiling built-in module, version information is stored in a separate
      section. Kernel then uses this data to create 'version' sysfs attribute
      in the same fashion it creates attributes for module parameters.
      Signed-off-by: default avatarDmitry Torokhov <dtor@vmware.com>
      Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      e94965ed
  4. 21 Jan, 2011 2 commits
  5. 20 Jan, 2011 3 commits
    • Rafael J. Wysocki's avatar
      ACPI: Introduce acpi_os_ioremap() · 2d6d9fd3
      Rafael J. Wysocki authored
      Commit ca9b600b ("ACPI / PM: Make suspend_nvs_save() use
      acpi_os_map_memory()") attempted to prevent the code in osl.c and nvs.c
      from using different ioremap() variants by making the latter use
      acpi_os_map_memory() for mapping the NVS pages.  However, that also
      requires acpi_os_unmap_memory() to be used for unmapping them, which
      causes synchronize_rcu() to be executed many times in a row
      unnecessarily and introduces substantial delays during resume on some
      systems.
      
      Instead of using acpi_os_map_memory() for mapping the NVS pages in nvs.c
      introduce acpi_os_ioremap() calling ioremap_cache() and make the code in
      both osl.c and nvs.c use it.
      Reported-by: default avatarJeff Chua <jeff.chua.linux@gmail.com>
      Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      2d6d9fd3
    • KAMEZAWA Hiroyuki's avatar
      memcg: fix USED bit handling at uncharge in THP · ca3e0214
      KAMEZAWA Hiroyuki authored
      Now, under THP:
      
      at charge:
        - PageCgroupUsed bit is set to all page_cgroup on a hugepage.
          ....set to 512 pages.
      at uncharge
        - PageCgroupUsed bit is unset on the head page.
      
      So, some pages will remain with "Used" bit.
      
      This patch fixes that Used bit is set only to the head page.
      Used bits for tail pages will be set at splitting if necessary.
      
      This patch adds this lock order:
         compound_lock() -> page_cgroup_move_lock().
      
      [akpm@linux-foundation.org: fix warning]
      Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
      Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ca3e0214
    • Tejun Heo's avatar
      lockdep: Move early boot local IRQ enable/disable status to init/main.c · 2ce802f6
      Tejun Heo authored
      During early boot, local IRQ is disabled until IRQ subsystem is
      properly initialized.  During this time, no one should enable
      local IRQ and some operations which usually are not allowed with
      IRQ disabled, e.g. operations which might sleep or require
      communications with other processors, are allowed.
      
      lockdep tracked this with early_boot_irqs_off/on() callbacks.
      As other subsystems need this information too, move it to
      init/main.c and make it generally available.  While at it,
      toggle the boolean to early_boot_irqs_disabled instead of
      enabled so that it can be initialized with %false and %true
      indicates the exceptional condition.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Acked-by: default avatarPekka Enberg <penberg@kernel.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      LKML-Reference: <20110120110635.GB6036@htj.dyndns.org>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      2ce802f6
  6. 19 Jan, 2011 7 commits
  7. 18 Jan, 2011 2 commits
  8. 17 Jan, 2011 4 commits
    • Roberto Sassu's avatar
      ecryptfs: moved ECRYPTFS_SUPER_MAGIC definition to linux/magic.h · 2a8652f4
      Roberto Sassu authored
      The definition of ECRYPTFS_SUPER_MAGIC has been moved to the include
      file 'linux/magic.h' to become available to other kernel subsystems.
      Signed-off-by: default avatarRoberto Sassu <roberto.sassu@polito.it>
      Signed-off-by: default avatarTyler Hicks <tyhicks@linux.vnet.ibm.com>
      2a8652f4
    • Namhyung Kim's avatar
      fs: fix address space warnings in ioctl_fiemap() · ecf5632d
      Namhyung Kim authored
      The fi_extents_start field of struct fiemap_extent_info is a
      user pointer but was not marked as __user. This makes sparse
      emit following warnings:
      
        CHECK   fs/ioctl.c
      fs/ioctl.c:114:26: warning: incorrect type in argument 1 (different address spaces)
      fs/ioctl.c:114:26:    expected void [noderef] <asn:1>*dst
      fs/ioctl.c:114:26:    got struct fiemap_extent *[assigned] dest
      fs/ioctl.c:202:14: warning: incorrect type in argument 1 (different address spaces)
      fs/ioctl.c:202:14:    expected void const volatile [noderef] <asn:1>*<noident>
      fs/ioctl.c:202:14:    got struct fiemap_extent *[assigned] fi_extents_start
      fs/ioctl.c:212:27: warning: incorrect type in argument 1 (different address spaces)
      fs/ioctl.c:212:27:    expected void [noderef] <asn:1>*dst
      fs/ioctl.c:212:27:    got char *<noident>
      
      Also add 'ufiemap' variable to eliminate unnecessary casts.
      Signed-off-by: default avatarNamhyung Kim <namhyung@gmail.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      ecf5632d
    • Steven Rostedt's avatar
      fs: Remove unlikely() from fput_light() · c2b3e74b
      Steven Rostedt authored
      In fput_light(), there's an unlikely(fput_needed), which running on
      my normal desktop doing firefox, xchat, evolution and part of my distcc farm,
      and running the annotate branch profiler shows that the unlikely is not
      very unlikely.
      
       correct incorrect  %        Function             File              Line
       ------- ---------  -        --------             ----              ----
             0       48 100 fput_light                file.h               26
      115828710 897415279  88 fput_light              file.h               26
      865271179 5286128445  85 fput_light             file.h               26
      19568539  8923664  31 fput_light                file.h               26
      12353677  3562279  22 fput_light                file.h               26
        267691    67062  20 fput_light                file.h               26
      15014853   348172   2 fput_light                file.h               26
        209258      205   0 fput_light                file.h               26
       1364164        0   0 fput_light                file.h               26
      
      Which gives 1032903812 times it was correct and 6203351846 times it was
      incorrect, or 85% incorrect.
      
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      c2b3e74b
    • Christoph Hellwig's avatar
      fallocate should be a file operation · 2fe17c10
      Christoph Hellwig authored
      Currently all filesystems except XFS implement fallocate asynchronously,
      while XFS forced a commit.  Both of these are suboptimal - in case of O_SYNC
      I/O we really want our allocation on disk, especially for the !KEEP_SIZE
      case where we actually grow the file with user-visible zeroes.  On the
      other hand always commiting the transaction is a bad idea for fast-path
      uses of fallocate like for example in recent Samba versions.   Given
      that block allocation is a data plane operation anyway change it from
      an inode operation to a file operation so that we have the file structure
      available that lets us check for O_SYNC.
      
      This also includes moving the code around for a few of the filesystems,
      and remove the already unnedded S_ISDIR checks given that we only wire
      up fallocate for regular files.
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      2fe17c10
  9. 16 Jan, 2011 5 commits
    • Tejun Heo's avatar
      RDMA: Update workqueue usage · f0626710
      Tejun Heo authored
      * ib_wq is added, which is used as the common workqueue for infiniband
        instead of the system workqueue.  All system workqueue usages
        including flush_scheduled_work() callers are converted to use and
        flush ib_wq.
      
      * cancel_delayed_work() + flush_scheduled_work() converted to
        cancel_delayed_work_sync().
      
      * qib_wq is removed and ib_wq is used instead.
      
      This is to prepare for deprecation of flush_scheduled_work().
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
      f0626710
    • Russell King - ARM Linux's avatar
      ARM: PL08x: cleanup comments · 94ae8522
      Russell King - ARM Linux authored
      Cleanup the formatting of comments, remove some which don't make sense
      anymore.
      Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      [fix conflict with 96a608a4]
      Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
      94ae8522
    • Andrea Arcangeli's avatar
      fix non-x86 build failure in pmdp_get_and_clear · b3697c02
      Andrea Arcangeli authored
      pmdp_get_and_clear/pmdp_clear_flush/pmdp_splitting_flush were trapped as
      BUG() and they were defined only to diminish the risk of build issues on
      not-x86 archs and to be consistent with the generic pte methods previously
      defined in include/asm-generic/pgtable.h.
      
      But they are causing more trouble than they were supposed to solve, so
      it's simpler not to define them when THP is off.
      
      This is also correcting the export of pmdp_splitting_flush which is
      currently unused (x86 isn't using the generic implementation in
      mm/pgtable-generic.c and no other arch needs that [yet]).
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Sam Ravnborg <sam@ravnborg.org>
      Cc: Stephen Rothwell <sfr@canb.auug.org.au>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: "Luck, Tony" <tony.luck@intel.com>
      Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      b3697c02
    • Rafael J. Wysocki's avatar
      PCI / ACPI: Fix build of the AER driver for CONFIG_ACPI unset · fc8fe1e9
      Rafael J. Wysocki authored
      After commit 415e12b2 ("PCI/ACPI: Request _OSC control once for each
      root bridge (v3)") include/linux/pci-acpi.h is included by
      drivers/pci/pcie/aer/aerdrv.c and if CONFIG_ACPI is unset, the bogus and
      unnecessary alternative definition of acpi_find_root_bridge_handle()
      causes a build error to occur.
      
      Remove the offending piece of garbage.
      Reported-and-tested-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
      Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      fc8fe1e9
    • Al Viro's avatar
      sanitize vfsmount refcounting changes · f03c6599
      Al Viro authored
      Instead of splitting refcount between (per-cpu) mnt_count
      and (SMP-only) mnt_longrefs, make all references contribute
      to mnt_count again and keep track of how many are longterm
      ones.
      
      Accounting rules for longterm count:
      	* 1 for each fs_struct.root.mnt
      	* 1 for each fs_struct.pwd.mnt
      	* 1 for having non-NULL ->mnt_ns
      	* decrement to 0 happens only under vfsmount lock exclusive
      
      That allows nice common case for mntput() - since we can't drop the
      final reference until after mnt_longterm has reached 0 due to the rules
      above, mntput() can grab vfsmount lock shared and check mnt_longterm.
      If it turns out to be non-zero (which is the common case), we know
      that this is not the final mntput() and can just blindly decrement
      percpu mnt_count.  Otherwise we grab vfsmount lock exclusive and
      do usual decrement-and-check of percpu mnt_count.
      
      For fs_struct.c we have mnt_make_longterm() and mnt_make_shortterm();
      namespace.c uses the latter in places where we don't already hold
      vfsmount lock exclusive and opencodes a few remaining spots where
      we need to manipulate mnt_longterm.
      
      Note that we mostly revert the code outside of fs/namespace.c back
      to what we used to have; in particular, normal code doesn't need
      to care about two kinds of references, etc.  And we get to keep
      the optimization Nick's variant had bought us...
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      f03c6599
  10. 15 Jan, 2011 8 commits
    • Grant Likely's avatar
      dt/flattree: Return virtual address from early_init_dt_alloc_memory_arch() · 672c5446
      Grant Likely authored
      The physical address is never used by the device tree code when
      allocating memory for unflattening.  Change the architecture's alloc
      hook to return the virutal address instead.
      Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
      672c5446
    • David Howells's avatar
      Unexport do_add_mount() and add in follow_automount(), not ->d_automount() · ea5b778a
      David Howells authored
      Unexport do_add_mount() and make ->d_automount() return the vfsmount to be
      added rather than calling do_add_mount() itself.  follow_automount() will then
      do the addition.
      
      This slightly complicates things as ->d_automount() normally wants to add the
      new vfsmount to an expiration list and start an expiration timer.  The problem
      with that is that the vfsmount will be deleted if it has a refcount of 1 and
      the timer will not repeat if the expiration list is empty.
      
      To this end, we require the vfsmount to be returned from d_automount() with a
      refcount of (at least) 2.  One of these refs will be dropped unconditionally.
      In addition, follow_automount() must get a 3rd ref around the call to
      do_add_mount() lest it eat a ref and return an error, leaving the mount we
      have open to being expired as we would otherwise have only 1 ref on it.
      
      d_automount() should also add the the vfsmount to the expiration list (by
      calling mnt_set_expiry()) and start the expiration timer before returning, if
      this mechanism is to be used.  The vfsmount will be unlinked from the
      expiration list by follow_automount() if do_add_mount() fails.
      
      This patch also fixes the call to do_add_mount() for AFS to propagate the mount
      flags from the parent vfsmount.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      ea5b778a
    • David Howells's avatar
      Allow d_manage() to be used in RCU-walk mode · ab90911f
      David Howells authored
      Allow d_manage() to be called from pathwalk when it is in RCU-walk mode as well
      as when it is in Ref-walk mode.  This permits __follow_mount_rcu() to call
      d_manage() directly.  d_manage() needs a parameter to indicate that it is in
      RCU-walk mode as it isn't allowed to sleep if in that mode (but should return
      -ECHILD instead).
      
      autofs4_d_manage() can then be set to retain RCU-walk mode if the daemon
      accesses it and otherwise request dropping back to ref-walk mode.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      ab90911f
    • Ian Kent's avatar
      autofs4: Bump version · 1972580b
      Ian Kent authored
      Increase the autofs module sub-version so we can tell what kernel
      implementation is being used from user space debug logging.
      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>
      1972580b
    • David Howells's avatar
      NFS: Use d_automount() rather than abusing follow_link() · 36d43a43
      David Howells authored
      Make NFS use the new d_automount() dentry operation rather than abusing
      follow_link() on directories.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Acked-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
      Acked-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      36d43a43
    • David Howells's avatar
      Add an AT_NO_AUTOMOUNT flag to suppress terminal automount · 6f45b656
      David Howells authored
      Add an AT_NO_AUTOMOUNT flag to suppress terminal automounting of automount
      point directories.  This can be used by fstatat() users to permit the
      gathering of attributes on an automount point and also prevent
      mass-automounting of a directory of automount points by ls.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Acked-by: default avatarIan Kent <raven@themaw.net>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      6f45b656
    • 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
    • David Howells's avatar
      Add a dentry op to handle automounting rather than abusing follow_link() · 9875cf80
      David Howells authored
      Add a dentry op (d_automount) to handle automounting directories rather than
      abusing the follow_link() inode operation.  The operation is keyed off a new
      dentry flag (DCACHE_NEED_AUTOMOUNT).
      
      This also makes it easier to add an AT_ flag to suppress terminal segment
      automount during pathwalk and removes the need for the kludge code in the
      pathwalk algorithm to handle directories with follow_link() semantics.
      
      The ->d_automount() dentry operation:
      
      	struct vfsmount *(*d_automount)(struct path *mountpoint);
      
      takes a pointer to the directory to be mounted upon, which is expected to
      provide sufficient data to determine what should be mounted.  If successful, it
      should return the vfsmount struct it creates (which it should also have added
      to the namespace using do_add_mount() or similar).  If there's a collision with
      another automount attempt, NULL should be returned.  If the directory specified
      by the parameter should be used directly rather than being mounted upon,
      -EISDIR should be returned.  In any other case, an error code should be
      returned.
      
      The ->d_automount() operation is called with no locks held and may sleep.  At
      this point the pathwalk algorithm will be in ref-walk mode.
      
      Within fs/namei.c itself, a new pathwalk subroutine (follow_automount()) is
      added to handle mountpoints.  It will return -EREMOTE if the automount flag was
      set, but no d_automount() op was supplied, -ELOOP if we've encountered too many
      symlinks or mountpoints, -EISDIR if the walk point should be used without
      mounting and 0 if successful.  The path will be updated to point to the mounted
      filesystem if a successful automount took place.
      
      __follow_mount() is replaced by follow_managed() which is more generic
      (especially with the patch that adds ->d_manage()).  This handles transits from
      directories during pathwalk, including automounting and skipping over
      mountpoints (and holding processes with the next patch).
      
      __follow_mount_rcu() will jump out of RCU-walk mode if it encounters an
      automount point with nothing mounted on it.
      
      follow_dotdot*() does not handle automounts as you don't want to trigger them
      whilst following "..".
      
      I've also extracted the mount/don't-mount logic from autofs4 and included it
      here.  It makes the mount go ahead anyway if someone calls open() or creat(),
      tries to traverse the directory, tries to chdir/chroot/etc. into the directory,
      or sticks a '/' on the end of the pathname.  If they do a stat(), however,
      they'll only trigger the automount if they didn't also say O_NOFOLLOW.
      
      I've also added an inode flag (S_AUTOMOUNT) so that filesystems can mark their
      inodes as automount points.  This flag is automatically propagated to the
      dentry as DCACHE_NEED_AUTOMOUNT by __d_instantiate().  This saves NFS and could
      save AFS a private flag bit apiece, but is not strictly necessary.  It would be
      preferable to do the propagation in d_set_d_op(), but that doesn't normally
      have access to the inode.
      
      [AV: fixed breakage in case if __follow_mount_rcu() fails and nameidata_drop_rcu()
      succeeds in RCU case of do_lookup(); we need to fall through to non-RCU case after
      that, rather than just returning with ungrabbed *path]
      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>
      9875cf80