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Message-ID: <768343b5-e9b4-a86c-53de-2929bc290342@gmail.com>
Date: Wed, 23 Nov 2016 09:37:13 +0100
From: "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To: David Howells <dhowells@...hat.com>, linux-fsdevel@...r.kernel.org
Cc: mtk.manpages@...il.com, linux-api@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] statx: Add a system call to make enhanced file info
available [ver #3]
Hi David,
On 11/23/2016 01:55 AM, David Howells wrote:
> Add a system call to make extended file information available, including
> file creation and some attribute flags where available through the
> underlying filesystem.
>
>
> ========
> OVERVIEW
> ========
>
> The idea was initially proposed as a set of xattrs that could be retrieved
> with getxattr(), but the general preferance proved to be for a new syscall
s/preferance/preference/
> with an extended stat structure.
>
> This can feasibly be used to support a number of things, not all of which
> are added here:
It would be very useful if this overview distinguishes which of the features
below are supported in the initial implementation, versus which features
(e.g., femtosecond timestamps) are simply allowed for in a future
implementation.
> (1) Better support for the y2038 problem [Arnd Bergmann].
>
> (2) 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.
>
> This is also specified in NFSv4 as a recommended attribute and could
> be exported by NFSD [Steve French].
>
> (3) 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].
>
> (4) Heavyweight stat: Force a netfs to go to the server, even if it thinks
> its cached attributes are up to date [Trond Myklebust].
>
> (5) 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.
>
> (6) 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].
>
> (7) 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
>
> (8) Extra coherency data may be useful in making backups [Andreas Dilger].
Can you elaborate on the point [8] in this commit message. It's not clear
to me at least what this is about.
>
> (9) 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...
>
> (10) Make the fields a consistent size on all arches and make them large.
>
> (11) Store a 16-byte volume ID in the superblock that can be returned in
> struct xstat [Steve French].
>
> (12) Include granularity fields in the time data to indicate the
> granularity of each of the times (NFSv4 time_delta) [Steve French].
>
> (13) 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).
>
> (14) Mask of features available on file (eg: ACLs, seclabel) [Brad Boyer,
> Michael Kerrisk].
>
> (15) Spare space, request flags and information flags are provided for
> future expansion.
>
> (16) Femtosecond-resolution timestamps [Dave Chinner].
>
>
> ===============
> NEW SYSTEM CALL
> ===============
>
> The new system call is:
>
> int ret = statx(int dfd,
> const char *filename,
> unsigned int flags,
In the 0/4 of this patch series, this argument is called 'atflags'.
These should be consistent. 'flags' seems correct to me.
> 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 (this typically only affects network filesystems) can be
> set by OR'ing a value into the flags argument:
s/can be set//
>
> (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 note that asking for
s/note/noted/
> 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@...romeda tmp]# ./samples/statx/test-statx -A /warthog/data
> statx(/warthog/data) = 0
> results=17ff
> Size: 4096 Blocks: 8 IO Block: 1048576 directory
> Device: 00:26 Inode: 1703937 Links: 124
> Access: (3777/drwxrwxrwx) Uid: 0 Gid: 4041
> Access: 2016-11-10 15:52:11.219935864+0000
> Modify: 2016-11-10 08:07:32.482314928+0000
> Change: 2016-11-10 08:07:32.482314928+0000
> Attributes: 0000000000001000 (-------- -------- -------- -------- -------- -------- ---m---- --------)
> IO-blocksize: blksize=1048576
>
> Secondly, the result of automounting on that directory.
>
> [root@...romeda tmp]# ./samples/statx/test-statx /warthog/data
> statx(/warthog/data) = 0
> results=17ff
> Size: 4096 Blocks: 8 IO Block: 1048576 directory
> Device: 00:27 Inode: 2 Links: 124
> Access: (3777/drwxrwxrwx) Uid: 0 Gid: 4041
> Access: 2016-11-10 15:52:11.219935864+0000
> Modify: 2016-11-10 08:07:32.482314928+0000
> Change: 2016-11-10 08:07:32.482314928+0000
> IO-blocksize: blksize=1048576
>
> Signed-off-by: David Howells <dhowells@...hat.com>
> ---
>
> arch/x86/entry/syscalls/syscall_32.tbl | 1
> arch/x86/entry/syscalls/syscall_64.tbl | 1
> fs/exportfs/expfs.c | 4
> fs/stat.c | 297 +++++++++++++++++++++++++++++---
> include/linux/fs.h | 5 -
> include/linux/stat.h | 19 +-
> include/linux/syscalls.h | 3
> include/uapi/linux/fcntl.h | 5 +
> include/uapi/linux/stat.h | 120 +++++++++++++
> samples/Kconfig | 5 +
> samples/Makefile | 3
> samples/statx/Makefile | 10 +
> samples/statx/test-statx.c | 248 +++++++++++++++++++++++++++
> 13 files changed, 681 insertions(+), 40 deletions(-)
> create mode 100644 samples/statx/Makefile
> create mode 100644 samples/statx/test-statx.c
>
> diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
> index 2b3618542544..9ba050fe47f3 100644
> --- a/arch/x86/entry/syscalls/syscall_32.tbl
> +++ b/arch/x86/entry/syscalls/syscall_32.tbl
> @@ -389,3 +389,4 @@
> 380 i386 pkey_mprotect sys_pkey_mprotect
> 381 i386 pkey_alloc sys_pkey_alloc
> 382 i386 pkey_free sys_pkey_free
> +383 i386 statx sys_statx
> diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
> index e93ef0b38db8..5aef183e2f85 100644
> --- a/arch/x86/entry/syscalls/syscall_64.tbl
> +++ b/arch/x86/entry/syscalls/syscall_64.tbl
> @@ -338,6 +338,7 @@
> 329 common pkey_mprotect sys_pkey_mprotect
> 330 common pkey_alloc sys_pkey_alloc
> 331 common pkey_free sys_pkey_free
> +332 common statx sys_statx
>
> #
> # x32-specific system call numbers start at 512 to avoid cache impact
> diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
> index a4b531be9168..2acc31751248 100644
> --- a/fs/exportfs/expfs.c
> +++ b/fs/exportfs/expfs.c
> @@ -299,7 +299,9 @@ static int get_name(const struct path *path, char *name, struct dentry *child)
> * filesystem supports 64-bit inode numbers. So we need to
> * actually call ->getattr, not just read i_ino:
> */
> - error = vfs_getattr_nosec(&child_path, &stat);
> + stat.query_flags = 0;
> + stat.request_mask = STATX_BASIC_STATS;
> + error = vfs_xgetattr_nosec(&child_path, &stat);
> if (error)
> return error;
> buffer.ino = stat.ino;
> diff --git a/fs/stat.c b/fs/stat.c
> index bc045c7994e1..82e656c42157 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -18,6 +18,15 @@
> #include <asm/uaccess.h>
> #include <asm/unistd.h>
>
> +/**
> + * generic_fillattr - Fill in the basic attributes from the inode struct
> + * @inode: Inode to use as the source
> + * @stat: Where to fill in the attributes
> + *
> + * Fill in the basic attributes in the kstat structure from data that's to be
> + * found on the VFS inode structure. This is the default if no getattr inode
> + * operation is supplied.
> + */
> void generic_fillattr(struct inode *inode, struct kstat *stat)
> {
> stat->dev = inode->i_sb->s_dev;
> @@ -27,87 +36,189 @@ void generic_fillattr(struct inode *inode, struct kstat *stat)
> stat->uid = inode->i_uid;
> stat->gid = inode->i_gid;
> stat->rdev = inode->i_rdev;
> - stat->size = i_size_read(inode);
> - stat->atime = inode->i_atime;
> stat->mtime = inode->i_mtime;
> stat->ctime = inode->i_ctime;
> - stat->blksize = (1 << inode->i_blkbits);
> + stat->size = i_size_read(inode);
> stat->blocks = inode->i_blocks;
> -}
> + stat->blksize = 1 << inode->i_blkbits;
>
> + stat->result_mask |= STATX_BASIC_STATS;
> + if (IS_NOATIME(inode))
> + stat->result_mask &= ~STATX_ATIME;
> + else
> + stat->atime = inode->i_atime;
> +
> + if (IS_AUTOMOUNT(inode))
> + stat->attributes |= STATX_ATTR_AUTOMOUNT;
> +}
> EXPORT_SYMBOL(generic_fillattr);
>
> /**
> - * vfs_getattr_nosec - getattr without security checks
> + * vfs_xgetattr_nosec - getattr without security checks
> * @path: file to get attributes from
> * @stat: structure to return attributes in
> *
> * Get attributes without calling security_inode_getattr.
> *
> - * Currently the only caller other than vfs_getattr is internal to the
> - * filehandle lookup code, which uses only the inode number and returns
> - * no attributes to any user. Any other code probably wants
> - * vfs_getattr.
> + * Currently the only caller other than vfs_xgetattr is internal to the
> + * filehandle lookup code, which uses only the inode number and returns no
> + * attributes to any user. Any other code probably wants vfs_xgetattr.
> + *
> + * The caller must set stat->request_mask to indicate what they want and
> + * stat->query_flags to indicate whether the server should be queried.
> */
> -int vfs_getattr_nosec(struct path *path, struct kstat *stat)
> +int vfs_xgetattr_nosec(struct path *path, struct kstat *stat)
> {
> struct inode *inode = d_backing_inode(path->dentry);
>
> + stat->query_flags &= ~KSTAT_QUERY_FLAGS;
> +
> + stat->result_mask = 0;
> + stat->attributes = 0;
> if (inode->i_op->getattr)
> return inode->i_op->getattr(path->mnt, path->dentry, stat);
>
> generic_fillattr(inode, stat);
> return 0;
> }
> +EXPORT_SYMBOL(vfs_xgetattr_nosec);
>
> -EXPORT_SYMBOL(vfs_getattr_nosec);
> -
> -int vfs_getattr(struct path *path, struct kstat *stat)
> +/*
> + * vfs_xgetattr - Get the enhanced basic attributes of a file
> + * @path: The file of interest
> + * @stat: Where to return the statistics
> + *
> + * Ask the filesystem for a file's attributes. The caller must have preset
> + * stat->request_mask and stat->query_flags to indicate what they want.
> + *
> + * If the file is remote, the filesystem can be forced to update the attributes
> + * from the backing store by passing AT_FORCE_ATTR_SYNC in query_flags or can
> + * suppress the update by passing AT_NO_ATTR_SYNC.
> + *
> + * Bits must have been set in stat->request_mask to indicate which attributes
> + * the caller wants retrieving. Any such attribute not requested may be
> + * returned anyway, but the value may be approximate, and, if remote, may not
> + * have been synchronised with the server.
> + *
> + * 0 will be returned on success, and a -ve error code if unsuccessful.
> + */
> +int vfs_xgetattr(struct path *path, struct kstat *stat)
> {
> int retval;
>
> retval = security_inode_getattr(path);
> if (retval)
> return retval;
> - return vfs_getattr_nosec(path, stat);
> + return vfs_xgetattr_nosec(path, stat);
> }
> +EXPORT_SYMBOL(vfs_xgetattr);
>
> +/**
> + * vfs_getattr - Get the basic attributes of a file
> + * @path: The file of interest
> + * @stat: Where to return the statistics
> + *
> + * Ask the filesystem for a file's attributes. If remote, the filesystem isn't
> + * forced to update its files from the backing store. Only the basic set of
> + * attributes will be retrieved; anyone wanting more must use vfs_xgetattr(),
> + * as must anyone who wants to force attributes to be sync'd with the server.
> + *
> + * 0 will be returned on success, and a -ve error code if unsuccessful.
> + */
> +int vfs_getattr(struct path *path, struct kstat *stat)
> +{
> + stat->query_flags = 0;
> + stat->request_mask = STATX_BASIC_STATS;
> + return vfs_xgetattr(path, stat);
> +}
> EXPORT_SYMBOL(vfs_getattr);
>
> -int vfs_fstat(unsigned int fd, struct kstat *stat)
> +/**
> + * vfs_fstatx - Get the enhanced basic attributes by file descriptor
> + * @fd: The file descriptor referring to the file of interest
> + * @stat: The result structure to fill in.
> + *
> + * This function is a wrapper around vfs_xgetattr(). The main difference is
> + * that it uses a file descriptor to determine the file location.
> + *
> + * The caller must have preset stat->query_flags and stat->request_mask as for
> + * vfs_xgetattr().
> + *
> + * 0 will be returned on success, and a -ve error code if unsuccessful.
> + */
> +int vfs_fstatx(unsigned int fd, struct kstat *stat)
> {
> struct fd f = fdget_raw(fd);
> int error = -EBADF;
>
> if (f.file) {
> - error = vfs_getattr(&f.file->f_path, stat);
> + error = vfs_xgetattr(&f.file->f_path, stat);
> fdput(f);
> }
> return error;
> }
> +EXPORT_SYMBOL(vfs_fstatx);
> +
> +/**
> + * vfs_fstat - Get basic attributes by file descriptor
> + * @fd: The file descriptor referring to the file of interest
> + * @stat: The result structure to fill in.
> + *
> + * This function is a wrapper around vfs_getattr(). The main difference is
> + * that it uses a file descriptor to determine the file location.
> + *
> + * 0 will be returned on success, and a -ve error code if unsuccessful.
> + */
> +int vfs_fstat(unsigned int fd, struct kstat *stat)
> +{
> + stat->query_flags = 0;
> + stat->request_mask = STATX_BASIC_STATS;
> + return vfs_fstatx(fd, stat);
> +}
> EXPORT_SYMBOL(vfs_fstat);
>
> -int vfs_fstatat(int dfd, const char __user *filename, struct kstat *stat,
> - int flag)
> +/**
> + * vfs_statx - Get basic and extra attributes by filename
> + * @dfd: A file descriptor representing the base dir for a relative filename
> + * @filename: The name of the file of interest
> + * @flags: Flags to control the query
> + * @stat: The result structure to fill in.
> + *
> + * This function is a wrapper around vfs_xgetattr(). The main difference is
> + * that it uses a filename and base directory to determine the file location.
> + * Additionally, the addition of AT_SYMLINK_NOFOLLOW to flags will prevent a
s/the addition of AT_SYMLINK_NOFOLLOW to/the use of AT_SYMLINK_NOFOLLOW in/
> + * symlink at the given name from being referenced.
> + *
> + * The caller must have preset stat->request_mask as for vfs_xgetattr(). The
> + * flags are also used to load up stat->query_flags.
> + *
> + * 0 will be returned on success, and a -ve error code if unsuccessful.
> + */
> +int vfs_statx(int dfd, const char __user *filename, int flags,
> + struct kstat *stat)
> {
> struct path path;
> int error = -EINVAL;
> - unsigned int lookup_flags = 0;
> + unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT;
>
> - if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT |
> - AT_EMPTY_PATH)) != 0)
> - goto out;
> + if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT |
> + AT_EMPTY_PATH | KSTAT_QUERY_FLAGS)) != 0)
> + return -EINVAL;
>
> - if (!(flag & AT_SYMLINK_NOFOLLOW))
> - lookup_flags |= LOOKUP_FOLLOW;
> - if (flag & AT_EMPTY_PATH)
> + if (flags & AT_SYMLINK_NOFOLLOW)
> + lookup_flags &= ~LOOKUP_FOLLOW;
> + if (flags & AT_NO_AUTOMOUNT)
> + lookup_flags &= ~LOOKUP_AUTOMOUNT;
> + if (flags & AT_EMPTY_PATH)
> lookup_flags |= LOOKUP_EMPTY;
> + stat->query_flags = flags;
> +
> retry:
> error = user_path_at(dfd, filename, lookup_flags, &path);
> if (error)
> goto out;
>
> - error = vfs_getattr(&path, stat);
> + error = vfs_xgetattr(&path, stat);
> path_put(&path);
> if (retry_estale(error, lookup_flags)) {
> lookup_flags |= LOOKUP_REVAL;
> @@ -116,17 +227,65 @@ int vfs_fstatat(int dfd, const char __user *filename, struct kstat *stat,
> out:
> return error;
> }
> +EXPORT_SYMBOL(vfs_statx);
> +
> +/**
> + * vfs_fstatat - Get basic attributes by filename
> + * @dfd: A file descriptor representing the base dir for a relative filename
> + * @filename: The name of the file of interest
> + * @flags: Flags to control the query
> + * @stat: The result structure to fill in.
> + *
> + * This function is a wrapper around vfs_statx(). The difference is that it
> + * preselects basic stats only. The flags are used to load up
> + * stat->query_flags in addition to indicating symlink handling during path
> + * resolution.
> + *
> + * 0 will be returned on success, and a -ve error code if unsuccessful.
> + */
> +int vfs_fstatat(int dfd, const char __user *filename, struct kstat *stat,
> + int flags)
> +{
> + stat->request_mask = STATX_BASIC_STATS;
> + return vfs_statx(dfd, filename, flags, stat);
> +}
> EXPORT_SYMBOL(vfs_fstatat);
>
> -int vfs_stat(const char __user *name, struct kstat *stat)
> +/**
> + * vfs_stat - Get basic attributes by filename
> + * @filename: The name of the file of interest
> + * @stat: The result structure to fill in.
> + *
> + * This function is a wrapper around vfs_statx(). The difference is that it
> + * preselects basic stats only, terminal symlinks are followed regardless and a
s/terminal symlinks/symlinks in the basename/
> + * remote filesystem can't be forced to query the server. If such is desired,
> + * vfs_statx() should be used instead.
> + *
> + * 0 will be returned on success, and a -ve error code if unsuccessful.
> + */
> +int vfs_stat(const char __user *filename, struct kstat *stat)
> {
> - return vfs_fstatat(AT_FDCWD, name, stat, 0);
> + stat->request_mask = STATX_BASIC_STATS;
> + return vfs_statx(AT_FDCWD, filename, 0, stat);
> }
> EXPORT_SYMBOL(vfs_stat);
>
> +/**
> + * vfs_lstat - Get basic attrs by filename, without following terminal symlink
> + * @filename: The name of the file of interest
> + * @stat: The result structure to fill in.
> + *
> + * This function is a wrapper around vfs_statx(). The difference is that it
> + * preselects basic stats only, terminal symlinks are note followed regardless
s/terminal symlinks/symlinks in the basename/
s/note/not/
> + * and a remote filesystem can't be forced to query the server. If such is
> + * desired, vfs_statx() should be used instead.
> + *
> + * 0 will be returned on success, and a -ve error code if unsuccessful.
> + */
> int vfs_lstat(const char __user *name, struct kstat *stat)
> {
> - return vfs_fstatat(AT_FDCWD, name, stat, AT_SYMLINK_NOFOLLOW);
> + stat->request_mask = STATX_BASIC_STATS;
> + return vfs_statx(AT_FDCWD, name, AT_SYMLINK_NOFOLLOW, stat);
> }
> EXPORT_SYMBOL(vfs_lstat);
>
> @@ -141,7 +300,7 @@ static int cp_old_stat(struct kstat *stat, struct __old_kernel_stat __user * sta
> {
> static int warncount = 5;
> struct __old_kernel_stat tmp;
> -
> +
> if (warncount > 0) {
> warncount--;
> printk(KERN_WARNING "VFS: Warning: %s using old stat() call. Recompile your binary.\n",
> @@ -166,7 +325,7 @@ static int cp_old_stat(struct kstat *stat, struct __old_kernel_stat __user * sta
> #if BITS_PER_LONG == 32
> if (stat->size > MAX_NON_LFS)
> return -EOVERFLOW;
> -#endif
> +#endif
> tmp.st_size = stat->size;
> tmp.st_atime = stat->atime.tv_sec;
> tmp.st_mtime = stat->mtime.tv_sec;
> @@ -443,6 +602,82 @@ SYSCALL_DEFINE4(fstatat64, int, dfd, const char __user *, filename,
> }
> #endif /* __ARCH_WANT_STAT64 || __ARCH_WANT_COMPAT_STAT64 */
>
> +/*
> + * Set the statx results.
> + */
> +static long statx_set_result(struct kstat *stat, struct statx __user *buffer)
> +{
> + uid_t uid = from_kuid_munged(current_user_ns(), stat->uid);
> + gid_t gid = from_kgid_munged(current_user_ns(), stat->gid);
> +
> +#define __put_timestamp(kts, uts) ( \
> + __put_user(kts.tv_sec, uts.tv_sec ) || \
> + __put_user(kts.tv_nsec, uts.tv_nsec ) || \
> + __put_user(0, uts.__reserved ))
> +
> + if (__put_user(stat->result_mask, &buffer->stx_mask ) ||
> + __put_user(stat->mode, &buffer->stx_mode ) ||
> + __clear_user(&buffer->__spare0, sizeof(buffer->__spare0)) ||
> + __put_user(stat->nlink, &buffer->stx_nlink ) ||
> + __put_user(uid, &buffer->stx_uid ) ||
> + __put_user(gid, &buffer->stx_gid ) ||
> + __put_user(stat->attributes, &buffer->stx_attributes ) ||
> + __put_user(stat->blksize, &buffer->stx_blksize ) ||
> + __put_user(MAJOR(stat->rdev), &buffer->stx_rdev_major ) ||
> + __put_user(MINOR(stat->rdev), &buffer->stx_rdev_minor ) ||
> + __put_user(MAJOR(stat->dev), &buffer->stx_dev_major ) ||
> + __put_user(MINOR(stat->dev), &buffer->stx_dev_minor ) ||
> + __put_timestamp(stat->atime, &buffer->stx_atime ) ||
> + __put_timestamp(stat->btime, &buffer->stx_btime ) ||
> + __put_timestamp(stat->ctime, &buffer->stx_ctime ) ||
> + __put_timestamp(stat->mtime, &buffer->stx_mtime ) ||
> + __put_user(stat->ino, &buffer->stx_ino ) ||
> + __put_user(stat->size, &buffer->stx_size ) ||
> + __put_user(stat->blocks, &buffer->stx_blocks ) ||
> + __clear_user(&buffer->__spare1, sizeof(buffer->__spare1)) ||
> + __clear_user(&buffer->__spare2, sizeof(buffer->__spare2)))
> + return -EFAULT;
> +
> + return 0;
> +}
> +
> +/**
> + * sys_statx - System call to get enhanced stats
> + * @dfd: Base directory to pathwalk from *or* fd to stat.
> + * @filename: File to stat *or* NULL.
> + * @flags: AT_* flags to control pathwalk.
> + * @mask: Parts of statx struct actually required.
> + * @buffer: Result buffer.
> + *
> + * Note that if filename is NULL, then it does the equivalent of fstat() using
> + * dfd to indicate the file of interest.
> + */
> +SYSCALL_DEFINE5(statx,
> + int, dfd, const char __user *, filename, unsigned, flags,
> + unsigned int, mask,
> + struct statx __user *, buffer)
> +{
> + struct kstat stat;
> + int error;
> +
> + if ((flags & AT_STATX_SYNC_TYPE) == AT_STATX_SYNC_TYPE)
> + return -EINVAL;
> + if (!access_ok(VERIFY_WRITE, buffer, sizeof(*buffer)))
> + return -EFAULT;
> +
> + memset(&stat, 0, sizeof(stat));
> + stat.query_flags = flags;
> + stat.request_mask = mask & STATX_ALL;
> +
> + if (filename)
> + error = vfs_statx(dfd, filename, flags, &stat);
> + else
> + error = vfs_fstatx(dfd, &stat);
> + if (error)
> + return error;
> + return statx_set_result(&stat, buffer);
> +}
> +
> /* Caller is here responsible for sufficient locking (ie. inode->i_lock) */
> void __inode_add_bytes(struct inode *inode, loff_t bytes)
> {
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 16d2b6e874d6..f153199566b4 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2916,8 +2916,9 @@ extern const struct inode_operations page_symlink_inode_operations;
> extern void kfree_link(void *);
> extern int generic_readlink(struct dentry *, char __user *, int);
> extern void generic_fillattr(struct inode *, struct kstat *);
> -int vfs_getattr_nosec(struct path *path, struct kstat *stat);
> +extern int vfs_xgetattr_nosec(struct path *path, struct kstat *stat);
> extern int vfs_getattr(struct path *, struct kstat *);
> +extern int vfs_xgetattr(struct path *, struct kstat *);
> void __inode_add_bytes(struct inode *inode, loff_t bytes);
> void inode_add_bytes(struct inode *inode, loff_t bytes);
> void __inode_sub_bytes(struct inode *inode, loff_t bytes);
> @@ -2935,6 +2936,8 @@ extern int vfs_lstat(const char __user *, struct kstat *);
> extern int vfs_fstat(unsigned int, struct kstat *);
> extern int vfs_fstatat(int , const char __user *, struct kstat *, int);
> extern const char *vfs_get_link(struct dentry *, struct delayed_call *);
> +extern int vfs_xstat(int, const char __user *, int, struct kstat *);
> +extern int vfs_xfstat(unsigned int, struct kstat *);
>
> extern int __generic_block_fiemap(struct inode *inode,
> struct fiemap_extent_info *fieinfo,
> diff --git a/include/linux/stat.h b/include/linux/stat.h
> index 075cb0c7eb2a..9b81dfcbb57a 100644
> --- a/include/linux/stat.h
> +++ b/include/linux/stat.h
> @@ -19,19 +19,26 @@
> #include <linux/uidgid.h>
>
> struct kstat {
> - u64 ino;
> - dev_t dev;
> + u32 query_flags; /* Operational flags */
> +#define KSTAT_QUERY_FLAGS (AT_STATX_SYNC_TYPE)
> + u32 request_mask; /* What fields the user asked for */
> + u32 result_mask; /* What fields the user got */
> umode_t mode;
> unsigned int nlink;
> + uint32_t blksize; /* Preferred I/O size */
> + u64 attributes;
> +#define KSTAT_ATTR_FS_IOC_FLAGS 0x00000874 /* Attrs corresponding to FS_*_FL flags */
> + u64 ino;
> + dev_t dev;
> + dev_t rdev;
> kuid_t uid;
> kgid_t gid;
> - dev_t rdev;
> loff_t size;
> - struct timespec atime;
> + struct timespec atime;
> struct timespec mtime;
> struct timespec ctime;
> - unsigned long blksize;
> - unsigned long long blocks;
> + struct timespec btime; /* File creation time */
> + u64 blocks;
> };
>
> #endif
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 91a740f6b884..980c3c9b06f8 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -48,6 +48,7 @@ struct stat;
> struct stat64;
> struct statfs;
> struct statfs64;
> +struct statx;
> struct __sysctl_args;
> struct sysinfo;
> struct timespec;
> @@ -902,5 +903,7 @@ asmlinkage long sys_pkey_mprotect(unsigned long start, size_t len,
> unsigned long prot, int pkey);
> asmlinkage long sys_pkey_alloc(unsigned long flags, unsigned long init_val);
> asmlinkage long sys_pkey_free(int pkey);
> +asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags,
> + unsigned mask, struct statx __user *buffer);
>
> #endif
> diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
> index beed138bd359..813afd6eee71 100644
> --- a/include/uapi/linux/fcntl.h
> +++ b/include/uapi/linux/fcntl.h
> @@ -63,5 +63,10 @@
> #define AT_NO_AUTOMOUNT 0x800 /* Suppress terminal automount traversal */
> #define AT_EMPTY_PATH 0x1000 /* Allow empty relative pathname */
>
> +#define AT_STATX_SYNC_TYPE 0x6000 /* Type of synchronisation required from statx() */
> +#define AT_STATX_SYNC_AS_STAT 0x0000 /* - Do whatever stat() does */
> +#define AT_STATX_FORCE_SYNC 0x2000 /* - Force the attributes to be sync'd with the server */
> +#define AT_STATX_DONT_SYNC 0x4000 /* - Don't sync attributes with the server */
> +
>
> #endif /* _UAPI_LINUX_FCNTL_H */
> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> index 7fec7e36d921..995e82fe019c 100644
> --- a/include/uapi/linux/stat.h
> +++ b/include/uapi/linux/stat.h
> @@ -1,6 +1,7 @@
> #ifndef _UAPI_LINUX_STAT_H
> #define _UAPI_LINUX_STAT_H
>
> +#include <linux/types.h>
>
> #if defined(__KERNEL__) || !defined(__GLIBC__) || (__GLIBC__ < 2)
>
> @@ -41,5 +42,124 @@
>
> #endif
>
> +/*
> + * Timestamp structure for the timestamps in struct statx.
> + */
> +struct statx_timestamp {
> + __s64 tv_sec; /* Number of seconds before or after midnight 1st Jan 1970 */
> + __s32 tv_nsec; /* Number of nanoseconds before or after sec (0-999,999,999) */
Here, add a note in the comment: "Will be a negative value (if nonzero) if tv_sec is negative"
[...]
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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