1. 29 Aug, 2018 1 commit
    • Arnd Bergmann's avatar
      y2038: Remove newstat family from default syscall set · 82b355d1
      Arnd Bergmann authored
      We have four generations of stat() syscalls:
      - the oldstat syscalls that are only used on the older architectures
      - the newstat family that is used on all 64-bit architectures but
        lacked support for large files on 32-bit architectures.
      - the stat64 family that is used mostly on 32-bit architectures to
        replace newstat
      - statx() to replace all of the above, adding 64-bit timestamps among
        other things.
      
      We already compile stat64 only on those architectures that need it,
      but newstat is always built, including on those that don't reference
      it. This adds a new __ARCH_WANT_NEW_STAT symbol along the lines of
      __ARCH_WANT_OLD_STAT and __ARCH_WANT_STAT64 to control compilation of
      newstat. All architectures that need it use an explict define, the
      others now get a little bit smaller, and future architecture (including
      64-bit targets) won't ever see it.
      Acked-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
      Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
      82b355d1
  2. 02 Apr, 2018 1 commit
  3. 02 Nov, 2017 1 commit
    • Greg Kroah-Hartman's avatar
      License cleanup: add SPDX GPL-2.0 license identifier to files with no license · b2441318
      Greg Kroah-Hartman authored
      Many source files in the tree are missing licensing information, which
      makes it harder for compliance tools to determine the correct license.
      
      By default all files without license information are under the default
      license of the kernel, which is GPL version 2.
      
      Update the files which contain no license information with the 'GPL-2.0'
      SPDX license identifier.  The SPDX identifier is a legally binding
      shorthand, which can be used instead of the full boiler plate text.
      
      This patch is based on work done by Thomas Gleixner and Kate Stewart and
      Philippe Ombredanne.
      
      How this work was done:
      
      Patches were generated and checked against linux-4.14-rc6 for a subset of
      the use cases:
       - file had no licensing information it it.
       - file was a */uapi/* one with no licensing information in it,
       - file was a */uapi/* one with existing licensing information,
      
      Further patches will be generated in subsequent months to fix up cases
      where non-standard license headers were used, and references to license
      had to be inferred by heuristics based on keywords.
      
      The analysis to determine which SPDX License Identifier to be applied to
      a file was done in a spreadsheet of side by side results from of the
      output of two independent scanners (ScanCode & Windriver) producing SPDX
      tag:value files created by Philippe Ombredanne.  Philippe prepared the
      base worksheet, and did an initial spot review of a few 1000 files.
      
      The 4.13 kernel was the starting point of the analysis with 60,537 files
      assessed.  Kate Stewart did a file by file comparison of the scanner
      results in the spreadsheet to determine which SPDX license identifier(s)
      to be applied to the file. She confirmed any determination that was not
      immediately clear with lawyers working with the Linux Foundation.
      
      Criteria used to select files for SPDX license identifier tagging was:
       - Files considered eligible had to be source code files.
       - Make and config files were included as candidates if they contained >5
         lines of source
       - File already had some variant of a license header in it (even if <5
         lines).
      
      All documentation files were explicitly excluded.
      
      The following heuristics were used to determine which SPDX license
      identifiers to apply.
      
       - when both scanners couldn't find any license traces, file was
         considered to have no license information in it, and the top level
         COPYING file license applied.
      
         For non */uapi/* files that summary was:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|-------
         GPL-2.0                                              11139
      
         and resulted in the first patch in this series.
      
         If that file was a */uapi/* path one, it was "GPL-2.0 WITH
         Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|-------
         GPL-2.0 WITH Linux-syscall-note                        930
      
         and resulted in the second patch in this series.
      
       - if a file had some form of licensing information in it, and was one
         of the */uapi/* ones, it was denoted with the Linux-syscall-note if
         any GPL family license was found in the file or had no licensing in
         it (per prior point).  Results summary:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|------
         GPL-2.0 WITH Linux-syscall-note                       270
         GPL-2.0+ WITH Linux-syscall-note                      169
         ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
         ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
         LGPL-2.1+ WITH Linux-syscall-note                      15
         GPL-1.0+ WITH Linux-syscall-note                       14
         ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
         LGPL-2.0+ WITH Linux-syscall-note                       4
         LGPL-2.1 WITH Linux-syscall-note                        3
         ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
         ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1
      
         and that resulted in the third patch in this series.
      
       - when the two scanners agreed on the detected license(s), that became
         the concluded license(s).
      
       - when there was disagreement between the two scanners (one detected a
         license but the other didn't, or they both detected different
         licenses) a manual inspection of the file occurred.
      
       - In most cases a manual inspection of the information in the file
         resulted in a clear resolution of the license that should apply (and
         which scanner probably needed to revisit its heuristics).
      
       - When it was not immediately clear, the license identifier was
         confirmed with lawyers working with the Linux Foundation.
      
       - If there was any question as to the appropriate license identifier,
         the file was flagged for further research and to be revisited later
         in time.
      
      In total, over 70 hours of logged manual review was done on the
      spreadsheet to determine the SPDX license identifiers to apply to the
      source files by Kate, Philippe, Thomas and, in some cases, confirmation
      by lawyers working with the Linux Foundation.
      
      Kate also obtained a third independent scan of the 4.13 code base from
      FOSSology, and compared selected files where the other two scanners
      disagreed against that SPDX file, to see if there was new insights.  The
      Windriver scanner is based on an older version of FOSSology in part, so
      they are related.
      
      Thomas did random spot checks in about 500 files from the spreadsheets
      for the uapi headers and agreed with SPDX license identifier in the
      files he inspected. For the non-uapi files Thomas did random spot checks
      in about 15000 files.
      
      In initial set of patches against 4.14-rc6, 3 files were found to have
      copy/paste license identifier errors, and have been fixed to reflect the
      correct identifier.
      
      Additionally Philippe spent 10 hours this week doing a detailed manual
      inspection and review of the 12,461 patched files from the initial patch
      version early this week with:
       - a full scancode scan run, collecting the matched texts, detected
         license ids and scores
       - reviewing anything where there was a license detected (about 500+
         files) to ensure that the applied SPDX license was correct
       - reviewing anything where there was no detection but the patch license
         was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
         SPDX license was correct
      
      This produced a worksheet with 20 files needing minor correction.  This
      worksheet was then exported into 3 different .csv files for the
      different types of files to be modified.
      
      These .csv files were then reviewed by Greg.  Thomas wrote a script to
      parse the csv files and add the proper SPDX tag to the file, in the
      format that the file expected.  This script was further refined by Greg
      based on the output to detect more types of files automatically and to
      distinguish between header and source .c files (which need different
      comment types.)  Finally Greg ran the script using the .csv files to
      generate the patches.
      Reviewed-by: default avatarKate Stewart <kstewart@linuxfoundation.org>
      Reviewed-by: default avatarPhilippe Ombredanne <pombredanne@nexb.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      b2441318
  4. 17 Aug, 2017 1 commit
    • Jan Kara's avatar
      fs: Provide __inode_get_bytes() · f4a8116a
      Jan Kara authored
      Provide helper __inode_get_bytes() which assumes i_lock is already
      acquired. Quota code will need this to be able to use i_lock to protect
      consistency of quota accounting information and inode usage.
      Signed-off-by: default avatarJan Kara <jack@suse.cz>
      f4a8116a
  5. 09 Jun, 2017 1 commit
  6. 27 Apr, 2017 1 commit
  7. 26 Apr, 2017 1 commit
    • David Howells's avatar
      statx: Kill fd-with-NULL-path support in favour of AT_EMPTY_PATH · 1e2f82d1
      David Howells authored
      With the new statx() syscall, the following both allow the attributes of
      the file attached to a file descriptor to be retrieved:
      
      	statx(dfd, NULL, 0, ...);
      
      and:
      
      	statx(dfd, "", AT_EMPTY_PATH, ...);
      
      Change the code to reject the first option, though this means copying
      the path and engaging pathwalk for the fstat() equivalent.  dfd can be a
      non-directory provided path is "".
      
      [ The timing of this isn't wonderful, but applying this now before we
        have statx() in any released kernel, before anybody starts using the
        NULL special case.    - Linus ]
      
      Fixes: a528d35e ("statx: Add a system call to make enhanced file info available")
      Reported-by: default avatarMichael Kerrisk <mtk.manpages@gmail.com>
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      cc: Eric Sandeen <sandeen@sandeen.net>
      cc: fstests@vger.kernel.org
      cc: linux-api@vger.kernel.org
      cc: linux-man@vger.kernel.org
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1e2f82d1
  8. 17 Apr, 2017 1 commit
  9. 03 Apr, 2017 5 commits
    • David Howells's avatar
      statx: Include a mask for stx_attributes in struct statx · 3209f68b
      David Howells authored
      Include a mask in struct stat to indicate which bits of stx_attributes the
      filesystem actually supports.
      
      This would also be useful if we add another system call that allows you to
      do a 'bulk attribute set' and pass in a statx struct with the masks
      appropriately set to say what you want to set.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      3209f68b
    • David Howells's avatar
      statx: Reserve the top bit of the mask for future struct expansion · 47071aee
      David Howells authored
      Reserve the top bit of the mask for future expansion of the statx struct
      and give an error if statx() sees it set.  All the other bits are ignored
      if we see them set but don't support the bit; we just clear the bit in the
      returned mask.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      47071aee
    • Eric Biggers's avatar
      statx: optimize copy of struct statx to userspace · 64bd7204
      Eric Biggers authored
      I found that statx() was significantly slower than stat().  As a
      microbenchmark, I compared 10,000,000 invocations of fstat() on a tmpfs
      file to the same with statx() passed a NULL path:
      
      	$ time ./stat_benchmark
      
      	real	0m1.464s
      	user	0m0.275s
      	sys	0m1.187s
      
      	$ time ./statx_benchmark
      
      	real	0m5.530s
      	user	0m0.281s
      	sys	0m5.247s
      
      statx is expected to be a little slower than stat because struct statx
      is larger than struct stat, but not by *that* much.  It turns out that
      most of the overhead was in copying struct statx to userspace, mostly in
      all the stac/clac instructions that got generated for each __put_user()
      call.  (This was on x86_64, but some other architectures, e.g. arm64,
      have something similar now too.)
      
      stat() instead initializes its struct on the stack and copies it to
      userspace with a single call to copy_to_user().  This turns out to be
      much faster, and changing statx to do this makes it almost as fast as
      stat:
      
      	$ time ./statx_benchmark
      
      	real	0m1.624s
      	user	0m0.270s
      	sys	0m1.354s
      
      For zeroing the reserved fields, start by zeroing the full struct with
      memset.  This makes it clear that every byte copied to userspace is
      initialized, even implicit padding bytes (though there are none
      currently).  In the scenarios I tested, it also performed the same as a
      designated initializer.  Manually initializing each field was still
      slightly faster, but would have been more error-prone and less
      verifiable.
      
      Also rename statx_set_result() to cp_statx() for consistency with
      cp_old_stat() et al., and make it noinline so that struct statx doesn't
      add to the stack usage during the main portion of the syscall execution.
      Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      64bd7204
    • Eric Biggers's avatar
      statx: remove incorrect part of vfs_statx() comment · b15fb70b
      Eric Biggers authored
      request_mask and query_flags are function arguments, not passed in
      struct kstat.  So remove the part of the comment which claims otherwise.
      This was apparently left over from an earlier version of the statx
      patch.
      Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      b15fb70b
    • Eric Biggers's avatar
      statx: reject unknown flags when using NULL path · 8c7493aa
      Eric Biggers authored
      The statx() system call currently accepts unknown flags when called with
      a NULL path to operate on a file descriptor.  Left unchanged, this could
      make it hard to introduce new query flags in the future, since
      applications may not be able to tell whether a given flag is supported.
      
      Fix this by failing the system call with EINVAL if any flags other than
      KSTAT_QUERY_FLAGS are specified in combination with a NULL path.
      
      Arguably, we could still permit known lookup-related flags such as
      AT_SYMLINK_NOFOLLOW.  However, that would be inconsistent with how
      sys_utimensat() behaves when passed a NULL path, which seems to be the
      closest precedent.  And given that the NULL path case is (I believe)
      mainly intended to be used to implement a wrapper function like fstatx()
      that doesn't have a path argument, I think rejecting lookup-related
      flags too is probably the best choice.
      Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      8c7493aa
  10. 03 Mar, 2017 1 commit
    • 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*()
      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: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      a528d35e
  11. 02 Mar, 2017 1 commit
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  17. 15 Apr, 2015 1 commit
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  23. 27 Sep, 2012 1 commit
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  25. 15 May, 2012 1 commit
  26. 07 May, 2012 2 commits
  27. 28 Apr, 2012 1 commit
  28. 21 Mar, 2012 1 commit
  29. 29 Feb, 2012 1 commit
  30. 02 Nov, 2011 1 commit
    • Andy Whitcroft's avatar
      readlinkat: ensure we return ENOENT for the empty pathname for normal lookups · 1fa1e7f6
      Andy Whitcroft authored
      Since the commit below which added O_PATH support to the *at() calls, the
      error return for readlink/readlinkat for the empty pathname has switched
      from ENOENT to EINVAL:
      
        commit 65cfc672
        Author: Al Viro <viro@zeniv.linux.org.uk>
        Date:   Sun Mar 13 15:56:26 2011 -0400
      
          readlinkat(), fchownat() and fstatat() with empty relative pathnames
      
      This is both unexpected for userspace and makes readlink/readlinkat
      inconsistant with all other interfaces; and inconsistant with our stated
      return for these pathnames.
      
      As the readlinkat call does not have a flags parameter we cannot use the
      AT_EMPTY_PATH approach used in the other calls.  Therefore expose whether
      the original path is infact entry via a new user_path_at_empty() path
      lookup function.  Use this to determine whether to default to EINVAL or
      ENOENT for failures.
      
      Addresses http://bugs.launchpad.net/bugs/817187
      
      [akpm@linux-foundation.org: remove unused getname_flags()]
      Signed-off-by: default avatarAndy Whitcroft <apw@canonical.com>
      Cc: Christoph Hellwig <hch@lst.de>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: <stable@kernel.org>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      1fa1e7f6
  31. 27 Sep, 2011 1 commit
    • Linus Torvalds's avatar
      vfs: remove LOOKUP_NO_AUTOMOUNT flag · b6c8069d
      Linus Torvalds authored
      That flag no longer makes sense, since we don't look up automount points
      as eagerly any more.  Additionally, it turns out that the NO_AUTOMOUNT
      handling was buggy to begin with: it would avoid automounting even for
      cases where we really *needed* to do the automount handling, and could
      return ENOENT for autofs entries that hadn't been instantiated yet.
      
      With our new non-eager automount semantics, one discussion has been
      about adding a AT_AUTOMOUNT flag to vfs_fstatat (and thus the
      newfstatat() and fstatat64() system calls), but it's probably not worth
      it: you can always force at least directory automounting by simply
      adding the final '/' to the filename, which works for *all* of the stat
      family system calls, old and new.
      
      So AT_NO_AUTOMOUNT (and thus LOOKUP_NO_AUTOMOUNT) really were just a
      result of our bad default behavior.
      Acked-by: default avatarIan Kent <raven@themaw.net>
      Acked-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      b6c8069d
  32. 07 Aug, 2011 1 commit
    • Linus Torvalds's avatar
      vfs: optimize inode cache access patterns · 3ddcd056
      Linus Torvalds authored
      The inode structure layout is largely random, and some of the vfs paths
      really do care.  The path lookup in particular is already quite D$
      intensive, and profiles show that accessing the 'inode->i_op->xyz'
      fields is quite costly.
      
      We already optimized the dcache to not unnecessarily load the d_op
      structure for members that are often NULL using the DCACHE_OP_xyz bits
      in dentry->d_flags, and this does something very similar for the inode
      ops that are used during pathname lookup.
      
      It also re-orders the fields so that the fields accessed by 'stat' are
      together at the beginning of the inode structure, and roughly in the
      order accessed.
      
      The effect of this seems to be in the 1-2% range for an empty kernel
      "make -j" run (which is fairly kernel-intensive, mostly in filename
      lookup), so it's visible.  The numbers are fairly noisy, though, and
      likely depend a lot on exact microarchitecture.  So there's more tuning
      to be done.
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      3ddcd056
  33. 15 Mar, 2011 1 commit