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a528d35e8b
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: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
168 lines
5.7 KiB
C
168 lines
5.7 KiB
C
/*
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* Copyright (C) 1995-1997 Olaf Kirch <okir@monad.swb.de>
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*/
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#ifndef LINUX_NFSD_VFS_H
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#define LINUX_NFSD_VFS_H
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#include "nfsfh.h"
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#include "nfsd.h"
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/*
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* Flags for nfsd_permission
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*/
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#define NFSD_MAY_NOP 0
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#define NFSD_MAY_EXEC 0x001 /* == MAY_EXEC */
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#define NFSD_MAY_WRITE 0x002 /* == MAY_WRITE */
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#define NFSD_MAY_READ 0x004 /* == MAY_READ */
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#define NFSD_MAY_SATTR 0x008
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#define NFSD_MAY_TRUNC 0x010
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#define NFSD_MAY_LOCK 0x020
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#define NFSD_MAY_MASK 0x03f
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/* extra hints to permission and open routines: */
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#define NFSD_MAY_OWNER_OVERRIDE 0x040
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#define NFSD_MAY_LOCAL_ACCESS 0x080 /* for device special files */
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#define NFSD_MAY_BYPASS_GSS_ON_ROOT 0x100
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#define NFSD_MAY_NOT_BREAK_LEASE 0x200
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#define NFSD_MAY_BYPASS_GSS 0x400
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#define NFSD_MAY_READ_IF_EXEC 0x800
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#define NFSD_MAY_64BIT_COOKIE 0x1000 /* 64 bit readdir cookies for >= NFSv3 */
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#define NFSD_MAY_CREATE (NFSD_MAY_EXEC|NFSD_MAY_WRITE)
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#define NFSD_MAY_REMOVE (NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC)
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/*
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* Callback function for readdir
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*/
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typedef int (*nfsd_filldir_t)(void *, const char *, int, loff_t, u64, unsigned);
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/* nfsd/vfs.c */
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int nfsd_racache_init(int);
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void nfsd_racache_shutdown(void);
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int nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp,
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struct svc_export **expp);
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__be32 nfsd_lookup(struct svc_rqst *, struct svc_fh *,
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const char *, unsigned int, struct svc_fh *);
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__be32 nfsd_lookup_dentry(struct svc_rqst *, struct svc_fh *,
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const char *, unsigned int,
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struct svc_export **, struct dentry **);
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__be32 nfsd_setattr(struct svc_rqst *, struct svc_fh *,
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struct iattr *, int, time_t);
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int nfsd_mountpoint(struct dentry *, struct svc_export *);
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#ifdef CONFIG_NFSD_V4
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__be32 nfsd4_set_nfs4_label(struct svc_rqst *, struct svc_fh *,
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struct xdr_netobj *);
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__be32 nfsd4_vfs_fallocate(struct svc_rqst *, struct svc_fh *,
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struct file *, loff_t, loff_t, int);
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__be32 nfsd4_clone_file_range(struct file *, u64, struct file *,
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u64, u64);
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#endif /* CONFIG_NFSD_V4 */
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__be32 nfsd_create_locked(struct svc_rqst *, struct svc_fh *,
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char *name, int len, struct iattr *attrs,
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int type, dev_t rdev, struct svc_fh *res);
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__be32 nfsd_create(struct svc_rqst *, struct svc_fh *,
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char *name, int len, struct iattr *attrs,
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int type, dev_t rdev, struct svc_fh *res);
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#ifdef CONFIG_NFSD_V3
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__be32 nfsd_access(struct svc_rqst *, struct svc_fh *, u32 *, u32 *);
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__be32 do_nfsd_create(struct svc_rqst *, struct svc_fh *,
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char *name, int len, struct iattr *attrs,
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struct svc_fh *res, int createmode,
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u32 *verifier, bool *truncp, bool *created);
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__be32 nfsd_commit(struct svc_rqst *, struct svc_fh *,
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loff_t, unsigned long);
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#endif /* CONFIG_NFSD_V3 */
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__be32 nfsd_open(struct svc_rqst *, struct svc_fh *, umode_t,
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int, struct file **);
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struct raparms;
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__be32 nfsd_splice_read(struct svc_rqst *,
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struct file *, loff_t, unsigned long *);
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__be32 nfsd_readv(struct file *, loff_t, struct kvec *, int,
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unsigned long *);
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__be32 nfsd_read(struct svc_rqst *, struct svc_fh *,
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loff_t, struct kvec *, int, unsigned long *);
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__be32 nfsd_write(struct svc_rqst *, struct svc_fh *, loff_t,
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struct kvec *, int, unsigned long *, int);
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__be32 nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
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struct file *file, loff_t offset,
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struct kvec *vec, int vlen, unsigned long *cnt,
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int stable);
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__be32 nfsd_readlink(struct svc_rqst *, struct svc_fh *,
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char *, int *);
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__be32 nfsd_symlink(struct svc_rqst *, struct svc_fh *,
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char *name, int len, char *path,
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struct svc_fh *res);
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__be32 nfsd_link(struct svc_rqst *, struct svc_fh *,
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char *, int, struct svc_fh *);
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ssize_t nfsd_copy_file_range(struct file *, u64,
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struct file *, u64, u64);
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__be32 nfsd_rename(struct svc_rqst *,
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struct svc_fh *, char *, int,
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struct svc_fh *, char *, int);
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__be32 nfsd_unlink(struct svc_rqst *, struct svc_fh *, int type,
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char *name, int len);
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__be32 nfsd_readdir(struct svc_rqst *, struct svc_fh *,
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loff_t *, struct readdir_cd *, nfsd_filldir_t);
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__be32 nfsd_statfs(struct svc_rqst *, struct svc_fh *,
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struct kstatfs *, int access);
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__be32 nfsd_permission(struct svc_rqst *, struct svc_export *,
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struct dentry *, int);
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struct raparms *nfsd_init_raparms(struct file *file);
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void nfsd_put_raparams(struct file *file, struct raparms *ra);
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static inline int fh_want_write(struct svc_fh *fh)
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{
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int ret = mnt_want_write(fh->fh_export->ex_path.mnt);
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if (!ret)
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fh->fh_want_write = true;
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return ret;
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}
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static inline void fh_drop_write(struct svc_fh *fh)
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{
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if (fh->fh_want_write) {
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fh->fh_want_write = false;
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mnt_drop_write(fh->fh_export->ex_path.mnt);
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}
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}
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static inline __be32 fh_getattr(struct svc_fh *fh, struct kstat *stat)
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{
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struct path p = {.mnt = fh->fh_export->ex_path.mnt,
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.dentry = fh->fh_dentry};
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return nfserrno(vfs_getattr(&p, stat, STATX_BASIC_STATS,
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AT_STATX_SYNC_AS_STAT));
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}
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static inline int nfsd_create_is_exclusive(int createmode)
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{
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return createmode == NFS3_CREATE_EXCLUSIVE
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|| createmode == NFS4_CREATE_EXCLUSIVE4_1;
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}
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static inline bool nfsd_eof_on_read(long requested, long read,
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loff_t offset, loff_t size)
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{
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/* We assume a short read means eof: */
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if (requested > read)
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return true;
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/*
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* A non-short read might also reach end of file. The spec
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* still requires us to set eof in that case.
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*
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* Further operations may have modified the file size since
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* the read, so the following check is not atomic with the read.
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* We've only seen that cause a problem for a client in the case
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* where the read returned a count of 0 without setting eof.
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* That case was fixed by the addition of the above check.
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*/
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return (offset + read >= size);
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}
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#endif /* LINUX_NFSD_VFS_H */
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