1. 05 10月, 2017 1 次提交
    • A
      ovl: fix regression caused by exclusive upper/work dir protection · 85fdee1e
      Amir Goldstein 提交于
      Enforcing exclusive ownership on upper/work dirs caused a docker
      regression: https://github.com/moby/moby/issues/34672.
      
      Euan spotted the regression and pointed to the offending commit.
      Vivek has brought the regression to my attention and provided this
      reproducer:
      
      Terminal 1:
      
        mount -t overlay -o workdir=work,lowerdir=lower,upperdir=upper none
              merged/
      
      Terminal 2:
      
        unshare -m
      
      Terminal 1:
      
        umount merged
        mount -t overlay -o workdir=work,lowerdir=lower,upperdir=upper none
              merged/
        mount: /root/overlay-testing/merged: none already mounted or mount point
               busy
      
      To fix the regression, I replaced the error with an alarming warning.
      With index feature enabled, mount does fail, but logs a suggestion to
      override exclusive dir protection by disabling index.
      Note that index=off mount does take the inuse locks, so a concurrent
      index=off will issue the warning and a concurrent index=on mount will fail.
      
      Documentation was updated to reflect this change.
      
      Fixes: 2cac0c00 ("ovl: get exclusive ownership on upper/work dirs")
      Cc: <stable@vger.kernel.org> # v4.13
      Reported-by: NEuan Kemp <euank@euank.com>
      Reported-by: NVivek Goyal <vgoyal@redhat.com>
      Signed-off-by: NAmir Goldstein <amir73il@gmail.com>
      Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>
      85fdee1e
  2. 17 9月, 2017 1 次提交
  3. 15 9月, 2017 1 次提交
  4. 07 9月, 2017 2 次提交
    • J
      fscache: remove unused ->now_uncached callback · 26b433d0
      Jan Kara 提交于
      Patch series "Ranged pagevec lookup", v2.
      
      In this series I make pagevec_lookup() update the index (to be
      consistent with pagevec_lookup_tag() and also as a preparation for
      ranged lookups), provide ranged variant of pagevec_lookup() and use it
      in places where it makes sense.  This not only removes some common code
      but is also a measurable performance win for some use cases (see patch
      4/10) where radix tree is sparse and searching & grabing of a page after
      the end of the range has measurable overhead.
      
      This patch (of 10):
      
      The callback doesn't ever get called.  Remove it.
      
      Link: http://lkml.kernel.org/r/20170726114704.7626-2-jack@suse.czSigned-off-by: NJan Kara <jack@suse.cz>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      26b433d0
    • R
      dax: use common 4k zero page for dax mmap reads · 91d25ba8
      Ross Zwisler 提交于
      When servicing mmap() reads from file holes the current DAX code
      allocates a page cache page of all zeroes and places the struct page
      pointer in the mapping->page_tree radix tree.
      
      This has three major drawbacks:
      
      1) It consumes memory unnecessarily. For every 4k page that is read via
         a DAX mmap() over a hole, we allocate a new page cache page. This
         means that if you read 1GiB worth of pages, you end up using 1GiB of
         zeroed memory. This is easily visible by looking at the overall
         memory consumption of the system or by looking at /proc/[pid]/smaps:
      
      	7f62e72b3000-7f63272b3000 rw-s 00000000 103:00 12   /root/dax/data
      	Size:            1048576 kB
      	Rss:             1048576 kB
      	Pss:             1048576 kB
      	Shared_Clean:          0 kB
      	Shared_Dirty:          0 kB
      	Private_Clean:   1048576 kB
      	Private_Dirty:         0 kB
      	Referenced:      1048576 kB
      	Anonymous:             0 kB
      	LazyFree:              0 kB
      	AnonHugePages:         0 kB
      	ShmemPmdMapped:        0 kB
      	Shared_Hugetlb:        0 kB
      	Private_Hugetlb:       0 kB
      	Swap:                  0 kB
      	SwapPss:               0 kB
      	KernelPageSize:        4 kB
      	MMUPageSize:           4 kB
      	Locked:                0 kB
      
      2) It is slower than using a common zero page because each page fault
         has more work to do. Instead of just inserting a common zero page we
         have to allocate a page cache page, zero it, and then insert it. Here
         are the average latencies of dax_load_hole() as measured by ftrace on
         a random test box:
      
          Old method, using zeroed page cache pages:	3.4 us
          New method, using the common 4k zero page:	0.8 us
      
         This was the average latency over 1 GiB of sequential reads done by
         this simple fio script:
      
           [global]
           size=1G
           filename=/root/dax/data
           fallocate=none
           [io]
           rw=read
           ioengine=mmap
      
      3) The fact that we had to check for both DAX exceptional entries and
         for page cache pages in the radix tree made the DAX code more
         complex.
      
      Solve these issues by following the lead of the DAX PMD code and using a
      common 4k zero page instead.  As with the PMD code we will now insert a
      DAX exceptional entry into the radix tree instead of a struct page
      pointer which allows us to remove all the special casing in the DAX
      code.
      
      Note that we do still pretty aggressively check for regular pages in the
      DAX radix tree, especially where we take action based on the bits set in
      the page.  If we ever find a regular page in our radix tree now that
      most likely means that someone besides DAX is inserting pages (which has
      happened lots of times in the past), and we want to find that out early
      and fail loudly.
      
      This solution also removes the extra memory consumption.  Here is that
      same /proc/[pid]/smaps after 1GiB of reading from a hole with the new
      code:
      
      	7f2054a74000-7f2094a74000 rw-s 00000000 103:00 12   /root/dax/data
      	Size:            1048576 kB
      	Rss:                   0 kB
      	Pss:                   0 kB
      	Shared_Clean:          0 kB
      	Shared_Dirty:          0 kB
      	Private_Clean:         0 kB
      	Private_Dirty:         0 kB
      	Referenced:            0 kB
      	Anonymous:             0 kB
      	LazyFree:              0 kB
      	AnonHugePages:         0 kB
      	ShmemPmdMapped:        0 kB
      	Shared_Hugetlb:        0 kB
      	Private_Hugetlb:       0 kB
      	Swap:                  0 kB
      	SwapPss:               0 kB
      	KernelPageSize:        4 kB
      	MMUPageSize:           4 kB
      	Locked:                0 kB
      
      Overall system memory consumption is similarly improved.
      
      Another major change is that we remove dax_pfn_mkwrite() from our fault
      flow, and instead rely on the page fault itself to make the PTE dirty
      and writeable.  The following description from the patch adding the
      vm_insert_mixed_mkwrite() call explains this a little more:
      
         "To be able to use the common 4k zero page in DAX we need to have our
          PTE fault path look more like our PMD fault path where a PTE entry
          can be marked as dirty and writeable as it is first inserted rather
          than waiting for a follow-up dax_pfn_mkwrite() =>
          finish_mkwrite_fault() call.
      
          Right now we can rely on having a dax_pfn_mkwrite() call because we
          can distinguish between these two cases in do_wp_page():
      
                  case 1: 4k zero page => writable DAX storage
                  case 2: read-only DAX storage => writeable DAX storage
      
          This distinction is made by via vm_normal_page(). vm_normal_page()
          returns false for the common 4k zero page, though, just as it does
          for DAX ptes. Instead of special casing the DAX + 4k zero page case
          we will simplify our DAX PTE page fault sequence so that it matches
          our DAX PMD sequence, and get rid of the dax_pfn_mkwrite() helper.
          We will instead use dax_iomap_fault() to handle write-protection
          faults.
      
          This means that insert_pfn() needs to follow the lead of
          insert_pfn_pmd() and allow us to pass in a 'mkwrite' flag. If
          'mkwrite' is set insert_pfn() will do the work that was previously
          done by wp_page_reuse() as part of the dax_pfn_mkwrite() call path"
      
      Link: http://lkml.kernel.org/r/20170724170616.25810-4-ross.zwisler@linux.intel.comSigned-off-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
      Reviewed-by: NJan Kara <jack@suse.cz>
      Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
      Cc: "Theodore Ts'o" <tytso@mit.edu>
      Cc: Alexander Viro <viro@zeniv.linux.org.uk>
      Cc: Andreas Dilger <adilger.kernel@dilger.ca>
      Cc: Christoph Hellwig <hch@lst.de>
      Cc: Dan Williams <dan.j.williams@intel.com>
      Cc: Dave Chinner <david@fromorbit.com>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Jonathan Corbet <corbet@lwn.net>
      Cc: Matthew Wilcox <mawilcox@microsoft.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      91d25ba8
  5. 05 9月, 2017 1 次提交
  6. 27 8月, 2017 1 次提交
  7. 22 8月, 2017 1 次提交
    • C
      f2fs: support journalled quota · 4b2414d0
      Chao Yu 提交于
      This patch supports to enable f2fs to accept quota information through
      mount option:
      - {usr,grp,prj}jquota=<quota file path>
      - jqfmt=<quota type>
      
      Then, in ->mount flow, we can recover quota file during log replaying,
      by this, journelled quota can be supported.
      Signed-off-by: NChao Yu <yuchao0@huawei.com>
      [Jaegeuk Kim: Fix wrong return values.]
      Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>
      4b2414d0
  8. 16 8月, 2017 1 次提交
  9. 01 8月, 2017 1 次提交
  10. 17 7月, 2017 1 次提交
    • D
      VFS: Differentiate mount flags (MS_*) from internal superblock flags · e462ec50
      David Howells 提交于
      Differentiate the MS_* flags passed to mount(2) from the internal flags set
      in the super_block's s_flags.  s_flags are now called SB_*, with the names
      and the values for the moment mirroring the MS_* flags that they're
      equivalent to.
      
      In this patch, just the headers are altered and some kernel code where
      blind automated conversion isn't necessarily correct.
      
      Note that this shows up some interesting issues:
      
       (1) Some MS_* flags get translated to MNT_* flags (such as MS_NODEV ->
           MNT_NODEV) without passing this on to the filesystem, but some
           filesystems set such flags anyway.
      
       (2) The ->remount_fs() methods of some filesystems adjust the *flags
           argument by setting MS_* flags in it, such as MS_NOATIME - but these
           flags are then scrubbed by do_remount_sb() (only the occupants of
           MS_RMT_MASK are permitted: MS_RDONLY, MS_SYNCHRONOUS, MS_MANDLOCK,
           MS_I_VERSION and MS_LAZYTIME)
      
      I'm not sure what's the best way to solve all these cases.
      Suggested-by: NAl Viro <viro@ZenIV.linux.org.uk>
      Signed-off-by: NDavid Howells <dhowells@redhat.com>
      e462ec50
  11. 13 7月, 2017 1 次提交
  12. 11 7月, 2017 2 次提交
    • D
      VFS: Kill off s_options and helpers · 1d278a87
      David Howells 提交于
      Kill off s_options, save/replace_mount_options() and generic_show_options()
      as all filesystems now implement ->show_options() for themselves.  This
      should make it easier to implement a context-based mount where the mount
      options can be passed individually over a file descriptor.
      Signed-off-by: NDavid Howells <dhowells@redhat.com>
      Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      1d278a87
    • L
      Fix up over-eager 'wait_queue_t' renaming · 7cee9384
      Linus Torvalds 提交于
      Commit ac6424b9 ("sched/wait: Rename wait_queue_t =>
      wait_queue_entry_t") had scripted the renaming incorrectly, and didn't
      actually check that the 'wait_queue_t' was a full token.
      
      As a result, it also triggered on 'wait_queue_token', and renamed that
      to 'wait_queue_entry_token' entry in the autofs4 packet structure
      definition too.  That was entirely incorrect, and not intended.
      
      The end result built fine when building just the kernel - because
      everything had been renamed consistently there - but caused problems in
      user space because the "struct autofs_packet_missing" type is exported
      as part of the uapi.
      
      This scripts it all back again:
      
          git grep -lw wait_queue_entry_token |
              xargs sed -i 's/wait_queue_entry_token/wait_queue_token/g'
      
      and checks the end result.
      Reported-by: NFlorian Fainelli <f.fainelli@gmail.com>
      Acked-by: NIngo Molnar <mingo@kernel.org>
      Fixes: ac6424b9 ("sched/wait: Rename wait_queue_t => wait_queue_entry_t")
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      7cee9384
  13. 09 7月, 2017 1 次提交
    • C
      f2fs: support plain user/group quota · 0abd675e
      Chao Yu 提交于
      This patch adds to support plain user/group quota.
      
      Change Note by Jaegeuk Kim.
      
      - Use f2fs page cache for quota files in order to consider garbage collection.
        so, quota files are not tolerable for sudden power-cuts, so user needs to do
        quotacheck.
      
      - setattr() calls dquot_transfer which will transfer inode->i_blocks.
        We can't reclaim that during f2fs_evict_inode(). So, we need to count
        node blocks as well in order to match i_blocks with dquot's space.
      
        Note that, Chao wrote a patch to count inode->i_blocks without inode block.
        (f2fs: don't count inode block in in-memory inode.i_blocks)
      
      - in f2fs_remount, we need to make RW in prior to dquot_resume.
      
      - handle fault_injection case during f2fs_quota_off_umount
      
      - TODO: Project quota
      Signed-off-by: NChao Yu <yuchao0@huawei.com>
      Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>
      0abd675e
  14. 06 7月, 2017 1 次提交
  15. 05 7月, 2017 1 次提交
  16. 04 7月, 2017 1 次提交
  17. 20 6月, 2017 1 次提交
    • I
      sched/wait: Rename wait_queue_t => wait_queue_entry_t · ac6424b9
      Ingo Molnar 提交于
      Rename:
      
      	wait_queue_t		=>	wait_queue_entry_t
      
      'wait_queue_t' was always a slight misnomer: its name implies that it's a "queue",
      but in reality it's a queue *entry*. The 'real' queue is the wait queue head,
      which had to carry the name.
      
      Start sorting this out by renaming it to 'wait_queue_entry_t'.
      
      This also allows the real structure name 'struct __wait_queue' to
      lose its double underscore and become 'struct wait_queue_entry',
      which is the more canonical nomenclature for such data types.
      
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: linux-kernel@vger.kernel.org
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      ac6424b9
  18. 19 5月, 2017 1 次提交
  19. 16 5月, 2017 3 次提交
  20. 13 5月, 2017 1 次提交
  21. 09 5月, 2017 1 次提交
  22. 05 5月, 2017 1 次提交
  23. 04 5月, 2017 1 次提交
  24. 21 4月, 2017 1 次提交
  25. 20 4月, 2017 1 次提交
  26. 19 4月, 2017 2 次提交
  27. 03 4月, 2017 1 次提交
  28. 30 3月, 2017 1 次提交
  29. 08 3月, 2017 1 次提交
  30. 03 3月, 2017 1 次提交
    • D
      statx: Add a system call to make enhanced file info available · a528d35e
      David Howells 提交于
      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*()
      function.
      
      Functions like vfs_stat() are now inline wrappers around new functions
      vfs_statx() and vfs_statx_fd() to reduce stack usage.
      
      ========
      OVERVIEW
      ========
      
      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
           __s64).
      
       (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]
           (AT_STATX_FORCE_SYNC).
      
      And the following have been left out for future extension:
      
       (7) Data version number: Could be used by userspace NFS servers [Aneesh
           Kumar].
      
           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.
      
      ===============
      NEW SYSTEM CALL
      ===============
      
      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
           respect.
      
       (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
           approximate.
      
      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
      size.
      
      ======================
      MAIN ATTRIBUTES RECORD
      ======================
      
      The following structures are defined in which to return the main attribute
      set:
      
      	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
      placed.
      
      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:
      
      	KSTAT_ATTR_FS_IOC_FLAGS
      
      [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.
      
      =======
      TESTING
      =======
      
      The following test program can be used to test the statx system call:
      
      	samples/statx/test-statx.c
      
      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
      	results=7ff
      	  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
      	results=7ff
      	  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: NDavid Howells <dhowells@redhat.com>
      Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      a528d35e
  31. 28 2月, 2017 4 次提交
  32. 24 2月, 2017 1 次提交