1. 19 Mar, 2017 12 commits
  2. 18 Mar, 2017 12 commits
    • Nicholas Bellinger's avatar
      tcmu: Convert cmd_time_out into backend device attribute · 7d7a7435
      Nicholas Bellinger authored
      Instead of putting cmd_time_out under ../target/core/user_0/foo/control,
      which has historically been used by parameters needed for initial
      backend device configuration, go ahead and move cmd_time_out into
      a backend device attribute.
      In order to do this, tcmu_module_init() has been updated to create
      a local struct configfs_attribute **tcmu_attrs, that is based upon
      the existing passthrough_attrib_attrs along with the new cmd_time_out
      attribute.  Once **tcm_attrs has been setup, go ahead and point
      it at tcmu_ops->tb_dev_attrib_attrs so it's picked up by target-core.
      Also following MNC's previous change, ->cmd_time_out is stored in
      milliseconds but exposed via configfs in seconds.  Also, note this
      patch restricts the modification of ->cmd_time_out to before +
      after the TCMU device has been configured, but not while it has
      active fabric exports.
      Cc: Mike Christie <mchristi@redhat.com>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Mike Christie's avatar
      tcmu: make cmd timeout configurable · af980e46
      Mike Christie authored
      A single daemon could implement multiple types of devices
      using multuple types of real devices that may not support
      restarting from crashes and/or handling tcmu timeouts. This
      makes the cmd timeout configurable, so handlers that do not
      support it can turn if off for now.
      Signed-off-by: default avatarMike Christie <mchristi@redhat.com>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Mike Christie's avatar
      tcmu: add helper to check if dev was configured · 972c7f16
      Mike Christie authored
      This adds a helper to check if the dev was configured. It
      will be used in the next patch to prevent updates to some
      config settings after the device has been setup.
      Signed-off-by: default avatarMike Christie <mchristi@redhat.com>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Mike Christie's avatar
      target: fix race during implicit transition work flushes · 760bf578
      Mike Christie authored
      This fixes the following races:
      1. core_alua_do_transition_tg_pt could have read
      tg_pt_gp_alua_access_state and gone into this if chunk:
      if (!explicit &&
              atomic_read(&tg_pt_gp->tg_pt_gp_alua_access_state) ==
      and then core_alua_do_transition_tg_pt_work could update the
      state. core_alua_do_transition_tg_pt would then only set
      tg_pt_gp_alua_pending_state and the tg_pt_gp_alua_access_state would
      not get updated with the second calls state.
      2. core_alua_do_transition_tg_pt could be setting
      tg_pt_gp_transition_complete while the tg_pt_gp_transition_work
      is already completing. core_alua_do_transition_tg_pt then waits on the
      completion that will never be called.
      To handle these issues, we just call flush_work which will return when
      core_alua_do_transition_tg_pt_work has completed so there is no need
      to do the complete/wait. And, if core_alua_do_transition_tg_pt_work
      was running, instead of trying to sneak in the state change, we just
      schedule up another core_alua_do_transition_tg_pt_work call.
      Note that this does not handle a possible race where there are multiple
      threads call core_alua_do_transition_tg_pt at the same time. I think
      we need a mutex in target_tg_pt_gp_alua_access_state_store.
      Signed-off-by: default avatarMike Christie <mchristi@redhat.com>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Mike Christie's avatar
      target: allow userspace to set state to transitioning · 1ca4d4fa
      Mike Christie authored
      Userspace target_core_user handlers like tcmu-runner may want to set the
      ALUA state to transitioning while it does implicit transitions. This
      patch allows that state when set from configfs.
      Signed-off-by: default avatarMike Christie <mchristi@redhat.com>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Mike Christie's avatar
      target: fix ALUA transition timeout handling · d7175373
      Mike Christie authored
      The implicit transition time tells initiators the min time
      to wait before timing out a transition. We currently schedule
      the transition to occur in tg_pt_gp_implicit_trans_secs
      seconds so there is no room for delays. If
      needs to write out info to a remote file, then the initiator can
      easily time out the operation.
      Signed-off-by: default avatarMike Christie <mchristi@redhat.com>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Mike Christie's avatar
      target: Use system workqueue for ALUA transitions · 207ee841
      Mike Christie authored
      If tcmu-runner is processing a STPG and needs to change the kernel's
      ALUA state then we cannot use the same work queue for task management
      requests and ALUA transitions, because we could deadlock. The problem
      occurs when a STPG times out before tcmu-runner is able to
      call into target_tg_pt_gp_alua_access_state_store->
      core_alua_do_port_transition -> core_alua_do_transition_tg_pt ->
      queue_work. In this case, the tmr is on the work queue waiting for
      the STPG to complete, but the STPG transition is now queued behind
      the waiting tmr.
      This bug will also be fixed by this patch:
      which switches the tmr code to use the system workqueues.
      For both, I am not sure if we need a dedicated workqueue since
      it is not a performance path and I do not think we need WQ_MEM_RECLAIM
      to make forward progress to free up memory like the block layer does.
      Signed-off-by: default avatarMike Christie <mchristi@redhat.com>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Mike Christie's avatar
      target: fail ALUA transitions for pscsi · 0a414572
      Mike Christie authored
      We do not setup the LU group for pscsi devices, so if you write
      a state to alua_access_state that will cause a transition you will
      get a NULL pointer dereference.
      This patch will fail attempts to try and transition the path
      for backend devices that set the TRANSPORT_FLAG_PASSTHROUGH_ALUA
      Signed-off-by: default avatarMike Christie <mchristi@redhat.com>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Mike Christie's avatar
      target: allow ALUA setup for some passthrough backends · 530c6891
      Mike Christie authored
      This patch allows passthrough backends to use the core/base LIO
      ALUA setup and state checks, but still handle the execution of
      This will allow the target_core_user module to execute STPG and RTPG
      in userspace, and not have to duplicate the ALUA state checks, path
      information (needed so we can check if command is executable on
      specific paths) and setup (rtslib sets/updates the configfs ALUA
      interface like it does for iblock or file).
      For STPG, the target_core_user userspace daemon, tcmu-runner will
      still execute the STPG, and to update the core/base LIO state it
      will use the existing configfs interface. For RTPG, tcmu-runner
      will loop over configfs and/or cache the state.
      Signed-off-by: default avatarMike Christie <mchristi@redhat.com>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Mike Christie's avatar
      tcmu: return on first Opt parse failure · 2579325c
      Mike Christie authored
      We only were returing failure if the last opt to be parsed failed.
      This has a return failure when we first detect a failure.
      Signed-off-by: default avatarMike Christie <mchristi@redhat.com>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Mike Christie's avatar
      tcmu: allow hw_max_sectors greater than 128 · 3abaa2bf
      Mike Christie authored
      tcmu hard codes the hw_max_sectors to 128 which is a litle small.
      Userspace uses the max_sectors to report the optimal IO size and
      some initiators perform better with larger IOs (open-iscsi seems
      to do better with 256 to 512 depending on the test).
      (Fix do not display hw max sectors twice - MNC)
      Signed-off-by: default avatarMike Christie <mchristi@redhat.com>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Nicholas Bellinger's avatar
      target: Drop pointless tfo->check_stop_free check · 9c28ca4f
      Nicholas Bellinger authored
      All in-tree fabric drivers provide a tfo->check_stop_free(),
      so there is no need to do the extra check within existing
      transport_cmd_check_stop_to_fabric() code.
      Just to be sure, add a check in target_fabric_tf_ops_check()
      to notify any out-of-tree drivers that might be missing it.
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
  3. 08 Mar, 2017 2 commits
    • Max Lohrmann's avatar
      target: Fix VERIFY_16 handling in sbc_parse_cdb · 13603685
      Max Lohrmann authored
      As reported by Max, the Windows 2008 R2 chkdsk utility expects
      VERIFY_16 to be supported, and does not handle the returned
      CHECK_CONDITION properly, resulting in an infinite loop.
      The kernel will log huge amounts of this error:
      kernel: TARGET_CORE[iSCSI]: Unsupported SCSI Opcode 0x8f, sending
      Signed-off-by: default avatarMax Lohrmann <post@wickenrode.com>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    • Nicholas Bellinger's avatar
      target/pscsi: Fix TYPE_TAPE + TYPE_MEDIMUM_CHANGER export · a04e54f2
      Nicholas Bellinger authored
      The following fixes a divide by zero OOPs with TYPE_TAPE
      due to pscsi_tape_read_blocksize() failing causing a zero
      sd->sector_size being propigated up via dev_attrib.hw_block_size.
      It also fixes another long-standing bug where TYPE_TAPE and
      TYPE_MEDIMUM_CHANGER where using pscsi_create_type_other(),
      which does not call scsi_device_get() to take the device
      reference.  Instead, rename pscsi_create_type_rom() to
      pscsi_create_type_nondisk() and use it for all cases.
      Finally, also drop a dump_stack() in pscsi_get_blocks() for
      non TYPE_DISK, which in modern target-core can get invoked
      via target_sense_desc_format() during CHECK_CONDITION.
      Reported-by: Malcolm Haak's avatarMalcolm Haak <insanemal@gmail.com>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
  4. 03 Mar, 2017 14 commits
    • Edward Cree's avatar
      sfc: fix IPID endianness in TSOv2 · 6d43131c
      Edward Cree authored
      The value we read from the header is in network byte order, whereas
       EFX_POPULATE_QWORD_* takes values in host byte order (which it then
       converts to little-endian, as MCDI is little-endian).
      Fixes: e9117e50 ("sfc: Firmware-Assisted TSO version 2")
      Signed-off-by: Edward Cree's avatarEdward Cree <ecree@solarflare.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    • Edward Cree's avatar
      sfc: avoid max() in array size · d0346b03
      Edward Cree authored
      It confuses sparse, which thinks the size isn't constant.  Let's achieve
       the same thing with a BUILD_BUG_ON, since we know which one should be
       bigger and don't expect them ever to change.
      Signed-off-by: Edward Cree's avatarEdward Cree <ecree@solarflare.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    • Jakub Kicinski's avatar
      nfp: correct DMA direction in XDP DMA sync · d58cebb7
      Jakub Kicinski authored
      dma_sync_single_for_*() takes the direction in which the buffer
      was mapped, not the direction of the sync.  We should sync XDP
      buffers bidirectionally.
      Fixes: ecd63a02 ("nfp: add XDP support in the driver")
      Signed-off-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    • Jakub Kicinski's avatar
      nfp: don't tell FW about the reserved buffer space · 9383b337
      Jakub Kicinski authored
      Since commit c0f031bc ("nfp_net: use alloc_frag() and build_skb()")
      we are allocating buffers which have to hold both the data and skb to
      be created in place by build_skb().
      FW should only be told about the buffer space it can DMA to, that
      is without the build_skb() headroom and tailroom.  Note: firmware
      applications should validate the buffers against both MTU and
      free list buffer size so oversized packets would not pass through
      the NIC anyway.
      Fixes: c0f031bc ("nfp: use alloc_frag() and build_skb()")
      Signed-off-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    • Hari Vyas's avatar
      net: ethernet: bgmac: mac address change bug · fa42245d
      Hari Vyas authored
      ndo_set_mac_address() passes struct sockaddr * as 2nd parameter to
      bgmac_set_mac_address() but code assumed u8 *.  This caused two bytes
      chopping and the wrong mac address was configured.
      Signed-off-by: default avatarHari Vyas <hariv@broadcom.com>
      Signed-off-by: default avatarJon Mason <jon.mason@broadcom.com>
      Fixes: 4e209001 ("bgmac: write mac address to hardware in ndo_set_mac_address")
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    • Jon Mason's avatar
      net: ethernet: bgmac: init sequence bug · 16206524
      Jon Mason authored
      Fix a bug in the 'bgmac' driver init sequence that blind writes for init
      sequence where it should preserve most bits other than the ones it is
      deliberately manipulating.
      The code now checks to see if the adapter needs to be brought out of
      reset (where as before it was doing an IDM write to bring it out of
      reset regardless of whether it was in reset or not).  Also, removed
      unnecessary usleeps (as there is already a read present to flush the
      IDM writes).
      Signed-off-by: default avatarZac Schroff <zschroff@broadcom.com>
      Signed-off-by: default avatarJon Mason <jon.mason@broadcom.com>
      Fixes: f6a95a24 ("net: ethernet: bgmac: Add platform device support")
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    • Paul Durrant's avatar
      xen-netback: don't vfree() queues under spinlock · a254d8f9
      Paul Durrant authored
      This leads to a BUG of the following form:
      [  174.512861] switch: port 2(vif3.0) entered disabled state
      [  174.522735] BUG: sleeping function called from invalid context at
      [  174.523451] in_atomic(): 1, irqs_disabled(): 0, pid: 28, name: xenwatch
      [  174.524131] CPU: 1 PID: 28 Comm: xenwatch Tainted: G        W
      4.10.0upstream-11073-g4977ab6e-dirty #1
      [  174.524819] Hardware name: MSI MS-7680/H61M-P23 (MS-7680), BIOS V17.0
      [  174.525517] Call Trace:
      [  174.526217]  show_stack+0x23/0x60
      [  174.526899]  dump_stack+0x5b/0x88
      [  174.527562]  ___might_sleep+0xde/0x130
      [  174.528208]  __might_sleep+0x35/0xa0
      [  174.528840]  ? _raw_spin_unlock_irqrestore+0x13/0x20
      [  174.529463]  ? __wake_up+0x40/0x50
      [  174.530089]  remove_vm_area+0x20/0x90
      [  174.530724]  __vunmap+0x1d/0xc0
      [  174.531346]  ? delete_object_full+0x13/0x20
      [  174.531973]  vfree+0x40/0x80
      [  174.532594]  set_backend_state+0x18a/0xa90
      [  174.533221]  ? dwc_scan_descriptors+0x24d/0x430
      [  174.533850]  ? kfree+0x5b/0xc0
      [  174.534476]  ? xenbus_read+0x3d/0x50
      [  174.535101]  ? xenbus_read+0x3d/0x50
      [  174.535718]  ? xenbus_gather+0x31/0x90
      [  174.536332]  ? ___might_sleep+0xf6/0x130
      [  174.536945]  frontend_changed+0x6b/0xd0
      [  174.537565]  xenbus_otherend_changed+0x7d/0x80
      [  174.538185]  frontend_changed+0x12/0x20
      [  174.538803]  xenwatch_thread+0x74/0x110
      [  174.539417]  ? woken_wake_function+0x20/0x20
      [  174.540049]  kthread+0xe5/0x120
      [  174.540663]  ? xenbus_printf+0x50/0x50
      [  174.541278]  ? __kthread_init_worker+0x40/0x40
      [  174.541898]  ret_from_fork+0x21/0x2c
      [  174.548635] switch: port 2(vif3.0) entered disabled state
      This patch defers the vfree() until after the spinlock is released.
      Reported-by: Juergen Gross's avatarJuergen Gross <jgross@suse.com>
      Signed-off-by: default avatarPaul Durrant <paul.durrant@citrix.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    • Paul Durrant's avatar
      xen-netback: keep a local pointer for vif in backend_disconnect() · d67ce7da
      Paul Durrant authored
      This patch replaces use of 'be->vif' with 'vif' and hence generally
      makes the function look tidier. No semantic change.
      Signed-off-by: default avatarPaul Durrant <paul.durrant@citrix.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    • Marc Kleine-Budde's avatar
      can: flexcan: fix typo in comment · 66ddb821
      Marc Kleine-Budde authored
      This patch fixes the typo "Disble" -> "Disable".
      Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
    • Marc Kleine-Budde's avatar
      can: usb_8dev: Fix memory leak of priv->cmd_msg_buffer · 7c426313
      Marc Kleine-Budde authored
      The priv->cmd_msg_buffer is allocated in the probe function, but never
      kfree()ed. This patch converts the kzalloc() to resource-managed
      Cc: linux-stable <stable@vger.kernel.org>
      Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
    • Ethan Zonca's avatar
      can: gs_usb: fix coding style · 540a27ae
      Ethan Zonca authored
      This patch fixes five minor style issues, spaces are between bitwise OR
      Signed-off-by: default avatarEthan Zonca <e@ethanzonca.com>
      Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
    • Ethan Zonca's avatar
      can: gs_usb: Don't use stack memory for USB transfers · c919a306
      Ethan Zonca authored
      Fixes: 05ca5270 can: gs_usb: add ethtool set_phys_id callback to locate physical device
      The gs_usb driver is performing USB transfers using buffers allocated on
      the stack. This causes the driver to not function with vmapped stacks.
      Instead, allocate memory for the transfer buffers.
      Signed-off-by: default avatarEthan Zonca <e@ethanzonca.com>
      Cc: linux-stable <stable@vger.kernel.org> # >= v4.8
      Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
    • Alexander Duyck's avatar
      ixgbe: Limit use of 2K buffers on architectures with 256B or larger cache lines · c74042f3
      Alexander Duyck authored
      On architectures that have a cache line size larger than 64 Bytes we start
      running into issues where the amount of headroom for the frame starts
      The size of skb_shared_info on a system with a 64B L1 cache line size is
      320.  This increases to 384 with a 128B cache line, and 512 with a 256B
      cache line.
      In addition the NET_SKB_PAD value increases as well consistent with the
      cache line size.  As a result when we get to a 256B cache line as seen on
      the s390 we end up 768 bytes used by padding and shared info leaving us
      with only 1280 bytes to use for data storage.  On architectures such as
      this we should default to using 3K Rx buffers out of a 8K page instead of
      trying to do 1.5K buffers out of a 4K page.
      To take all of this into account I have added one small check so that we
      compare the max_frame to the amount of actual data we can store.  This was
      already occurring for igb, but I had overlooked it for ixgbe as it doesn't
      have strict limits for 82599 once we enable jumbo frames.  By adding this
      check we will automatically enable 3K Rx buffers as soon as the maximum
      frame size we can handle drops below the standard Ethernet MTU.
      I also went through and fixed one small typo that I found where I had left
      an IGB in a variable name due to a copy/paste error.
      Signed-off-by: default avatarAlexander Duyck <alexander.h.duyck@intel.com>
      Tested-by: default avatarAndrew Bowers <andrewx.bowers@intel.com>
      Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
    • David Howells's avatar
      statx: Add a system call to make enhanced file info available · a528d35e
      David Howells authored
      Add a system call to make extended file information available, including
      file creation and some attribute flags where available through the
      underlying filesystem.
      The getattr inode operation is altered to take two additional arguments: a
      u32 request_mask and an unsigned int flags that indicate the
      synchronisation mode.  This change is propagated to the vfs_getattr*()
      Functions like vfs_stat() are now inline wrappers around new functions
      vfs_statx() and vfs_statx_fd() to reduce stack usage.
      The idea was initially proposed as a set of xattrs that could be retrieved
      with getxattr(), but the general preference proved to be for a new syscall
      with an extended stat structure.
      A number of requests were gathered for features to be included.  The
      following have been included:
       (1) Make the fields a consistent size on all arches and make them large.
       (2) Spare space, request flags and information flags are provided for
           future expansion.
       (3) Better support for the y2038 problem [Arnd Bergmann] (tv_sec is an
       (4) Creation time: The SMB protocol carries the creation time, which could
           be exported by Samba, which will in turn help CIFS make use of
           FS-Cache as that can be used for coherency data (stx_btime).
           This is also specified in NFSv4 as a recommended attribute and could
           be exported by NFSD [Steve French].
       (5) Lightweight stat: Ask for just those details of interest, and allow a
           netfs (such as NFS) to approximate anything not of interest, possibly
           without going to the server [Trond Myklebust, Ulrich Drepper, Andreas
           Dilger] (AT_STATX_DONT_SYNC).
       (6) Heavyweight stat: Force a netfs to go to the server, even if it thinks
           its cached attributes are up to date [Trond Myklebust]
      And the following have been left out for future extension:
       (7) Data version number: Could be used by userspace NFS servers [Aneesh
           Can also be used to modify fill_post_wcc() in NFSD which retrieves
           i_version directly, but has just called vfs_getattr().  It could get
           it from the kstat struct if it used vfs_xgetattr() instead.
           (There's disagreement on the exact semantics of a single field, since
           not all filesystems do this the same way).
       (8) BSD stat compatibility: Including more fields from the BSD stat such
           as creation time (st_btime) and inode generation number (st_gen)
           [Jeremy Allison, Bernd Schubert].
       (9) Inode generation number: Useful for FUSE and userspace NFS servers
           [Bernd Schubert].
           (This was asked for but later deemed unnecessary with the
           open-by-handle capability available and caused disagreement as to
           whether it's a security hole or not).
      (10) Extra coherency data may be useful in making backups [Andreas Dilger].
           (No particular data were offered, but things like last backup
           timestamp, the data version number and the DOS archive bit would come
           into this category).
      (11) Allow the filesystem to indicate what it can/cannot provide: A
           filesystem can now say it doesn't support a standard stat feature if
           that isn't available, so if, for instance, inode numbers or UIDs don't
           exist or are fabricated locally...
           (This requires a separate system call - I have an fsinfo() call idea
           for this).
      (12) Store a 16-byte volume ID in the superblock that can be returned in
           struct xstat [Steve French].
           (Deferred to fsinfo).
      (13) Include granularity fields in the time data to indicate the
           granularity of each of the times (NFSv4 time_delta) [Steve French].
           (Deferred to fsinfo).
      (14) FS_IOC_GETFLAGS value.  These could be translated to BSD's st_flags.
           Note that the Linux IOC flags are a mess and filesystems such as Ext4
           define flags that aren't in linux/fs.h, so translation in the kernel
           may be a necessity (or, possibly, we provide the filesystem type too).
           (Some attributes are made available in stx_attributes, but the general
           feeling was that the IOC flags were to ext[234]-specific and shouldn't
           be exposed through statx this way).
      (15) Mask of features available on file (eg: ACLs, seclabel) [Brad Boyer,
           Michael Kerrisk].
           (Deferred, probably to fsinfo.  Finding out if there's an ACL or
           seclabal might require extra filesystem operations).
      (16) Femtosecond-resolution timestamps [Dave Chinner].
           (A __reserved field has been left in the statx_timestamp struct for
           this - if there proves to be a need).
      (17) A set multiple attributes syscall to go with this.
      The new system call is:
      	int ret = statx(int dfd,
      			const char *filename,
      			unsigned int flags,
      			unsigned int mask,
      			struct statx *buffer);
      The dfd, filename and flags parameters indicate the file to query, in a
      similar way to fstatat().  There is no equivalent of lstat() as that can be
      emulated with statx() by passing AT_SYMLINK_NOFOLLOW in flags.  There is
      also no equivalent of fstat() as that can be emulated by passing a NULL
      filename to statx() with the fd of interest in dfd.
      Whether or not statx() synchronises the attributes with the backing store
      can be controlled by OR'ing a value into the flags argument (this typically
      only affects network filesystems):
       (1) AT_STATX_SYNC_AS_STAT tells statx() to behave as stat() does in this
       (2) AT_STATX_FORCE_SYNC will require a network filesystem to synchronise
           its attributes with the server - which might require data writeback to
           occur to get the timestamps correct.
       (3) AT_STATX_DONT_SYNC will suppress synchronisation with the server in a
           network filesystem.  The resulting values should be considered
      mask is a bitmask indicating the fields in struct statx that are of
      interest to the caller.  The user should set this to STATX_BASIC_STATS to
      get the basic set returned by stat().  It should be noted that asking for
      more information may entail extra I/O operations.
      buffer points to the destination for the data.  This must be 256 bytes in
      The following structures are defined in which to return the main attribute
      	struct statx_timestamp {
      		__s64	tv_sec;
      		__s32	tv_nsec;
      		__s32	__reserved;
      	struct statx {
      		__u32	stx_mask;
      		__u32	stx_blksize;
      		__u64	stx_attributes;
      		__u32	stx_nlink;
      		__u32	stx_uid;
      		__u32	stx_gid;
      		__u16	stx_mode;
      		__u16	__spare0[1];
      		__u64	stx_ino;
      		__u64	stx_size;
      		__u64	stx_blocks;
      		__u64	__spare1[1];
      		struct statx_timestamp	stx_atime;
      		struct statx_timestamp	stx_btime;
      		struct statx_timestamp	stx_ctime;
      		struct statx_timestamp	stx_mtime;
      		__u32	stx_rdev_major;
      		__u32	stx_rdev_minor;
      		__u32	stx_dev_major;
      		__u32	stx_dev_minor;
      		__u64	__spare2[14];
      The defined bits in request_mask and stx_mask are:
      	STATX_TYPE		Want/got stx_mode & S_IFMT
      	STATX_MODE		Want/got stx_mode & ~S_IFMT
      	STATX_NLINK		Want/got stx_nlink
      	STATX_UID		Want/got stx_uid
      	STATX_GID		Want/got stx_gid
      	STATX_ATIME		Want/got stx_atime{,_ns}
      	STATX_MTIME		Want/got stx_mtime{,_ns}
      	STATX_CTIME		Want/got stx_ctime{,_ns}
      	STATX_INO		Want/got stx_ino
      	STATX_SIZE		Want/got stx_size
      	STATX_BLOCKS		Want/got stx_blocks
      	STATX_BASIC_STATS	[The stuff in the normal stat struct]
      	STATX_BTIME		Want/got stx_btime{,_ns}
      	STATX_ALL		[All currently available stuff]
      stx_btime is the file creation time, stx_mask is a bitmask indicating the
      data provided and __spares*[] are where as-yet undefined fields can be
      Time fields are structures with separate seconds and nanoseconds fields
      plus a reserved field in case we want to add even finer resolution.  Note
      that times will be negative if before 1970; in such a case, the nanosecond
      fields will also be negative if not zero.
      The bits defined in the stx_attributes field convey information about a
      file, how it is accessed, where it is and what it does.  The following
      attributes map to FS_*_FL flags and are the same numerical value:
      	STATX_ATTR_COMPRESSED		File is compressed by the fs
      	STATX_ATTR_IMMUTABLE		File is marked immutable
      	STATX_ATTR_APPEND		File is append-only
      	STATX_ATTR_NODUMP		File is not to be dumped
      	STATX_ATTR_ENCRYPTED		File requires key to decrypt in fs
      Within the kernel, the supported flags are listed by:
      [Are any other IOC flags of sufficient general interest to be exposed
      through this interface?]
      New flags include:
      	STATX_ATTR_AUTOMOUNT		Object is an automount trigger
      These are for the use of GUI tools that might want to mark files specially,
      depending on what they are.
      Fields in struct statx come in a number of classes:
       (0) stx_dev_*, stx_blksize.
           These are local system information and are always available.
       (1) stx_mode, stx_nlinks, stx_uid, stx_gid, stx_[amc]time, stx_ino,
           stx_size, stx_blocks.
           These will be returned whether the caller asks for them or not.  The
           corresponding bits in stx_mask will be set to indicate whether they
           actually have valid values.
           If the caller didn't ask for them, then they may be approximated.  For
           example, NFS won't waste any time updating them from the server,
           unless as a byproduct of updating something requested.
           If the values don't actually exist for the underlying object (such as
           UID or GID on a DOS file), then the bit won't be set in the stx_mask,
           even if the caller asked for the value.  In such a case, the returned
           value will be a fabrication.
           Note that there are instances where the type might not be valid, for
           instance Windows reparse points.
       (2) stx_rdev_*.
           This will be set only if stx_mode indicates we're looking at a
           blockdev or a chardev, otherwise will be 0.
       (3) stx_btime.
           Similar to (1), except this will be set to 0 if it doesn't exist.
      The following test program can be used to test the statx system call:
      Just compile and run, passing it paths to the files you want to examine.
      The file is built automatically if CONFIG_SAMPLES is enabled.
      Here's some example output.  Firstly, an NFS directory that crosses to
      another FSID.  Note that the AUTOMOUNT attribute is set because transiting
      this directory will cause d_automount to be invoked by the VFS.
      	[root@andromeda ~]# /tmp/test-statx -A /warthog/data
      	statx(/warthog/data) = 0
      	  Size: 4096            Blocks: 8          IO Block: 1048576  directory
      	Device: 00:26           Inode: 1703937     Links: 125
      	Access: (3777/drwxrwxrwx)  Uid:     0   Gid:  4041
      	Access: 2016-11-24 09:02:12.219699527+0000
      	Modify: 2016-11-17 10:44:36.225653653+0000
      	Change: 2016-11-17 10:44:36.225653653+0000
      	Attributes: 0000000000001000 (-------- -------- -------- -------- -------- -------- ---m---- --------)
      Secondly, the result of automounting on that directory.
      	[root@andromeda ~]# /tmp/test-statx /warthog/data
      	statx(/warthog/data) = 0
      	  Size: 4096            Blocks: 8          IO Block: 1048576  directory
      	Device: 00:27           Inode: 2           Links: 125
      	Access: (3777/drwxrwxrwx)  Uid:     0   Gid:  4041
      	Access: 2016-11-24 09:02:12.219699527+0000
      	Modify: 2016-11-17 10:44:36.225653653+0000
      	Change: 2016-11-17 10:44:36.225653653+0000
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>