Re: [PATCH v6 1/2] man/man2: introduce man page for file_getattr(2) syscall

[Alejandro Colomar <alx@kernel.org>]

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Hi Andrey,

> Date: 2026-10-21 16:10:04+0200
> From: Andrey Albershteyn <aalbersh@kernel.org>
>
> Add manual page for file_getattr().
> 
> Link: https://lore.kernel.org/all/20250630-xattrat-syscall-v6-0-c4e3bc35227b@kernel.org/
> Reviewed-by: Alejandro Colomar <alx@kernel.org>
> Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>

Thanks!  I've applied the patch (with very minor tweaks in the commit
message an the diff).


Have a lovely day!
Alex

> ---
>  man/man2/file_getattr.2 | 252 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 252 insertions(+)
>  create mode 100644 man/man2/file_getattr.2
> 
> diff --git a/man/man2/file_getattr.2 b/man/man2/file_getattr.2
> new file mode 100644
> index 000000000000..9963eeaa7caf
> --- /dev/null
> +++ b/man/man2/file_getattr.2
> @@ -0,0 +1,252 @@
> +.\" Copyright, the authors of the Linux man-pages project
> +.\"
> +.\" SPDX-License-Identifier: Linux-man-pages-copyleft
> +.\"
> +.TH file_getattr 2 (date) "Linux man-pages (unreleased)"
> +.SH NAME
> +file_getattr \- get filesystem file attributes
> +.SH SYNOPSIS
> +.nf
> +.BR "#include <linux/fcntl.h>" "      /* " AT_* " constants */"
> +.BR "#include <linux/fs.h>" "         /* " FS_XFLAG_* " constants */"
> +.BR "#include <sys/syscall.h>" "      /* " SYS_* " constants */"
> +.B #include <unistd.h>
> +.P
> +.B long syscall(SYS_file_getattr,
> +.BI "               int " dirfd ", const char *" path ,
> +.BI "               struct file_attr *" fattr ", size_t " size ,
> +.BI "               unsigned int " flags );
> +.fi
> +.SH DESCRIPTION
> +The
> +.BR file_getattr ()
> +system call retrieves filesystem file attributes
> +of the file
> +specified by path.
> +.P
> +The
> +.I dirfd
> +and
> +.I path
> +arguments behave in the same way as in
> +.BR openat (2),
> +with the difference that
> +.I path
> +can be NULL meaning an empty string.
> +.P
> +The
> +.I fattr
> +argument is a pointer to a
> +.I file_attr
> +structure.
> +This structure will be filled with file attributes.
> +This structure is described in
> +.BR file_attr (2type).
> +.P
> +The
> +.I size
> +argument specifies the size of the structure pointed to by
> +.IR fattr .
> +The size indicates the version of the structure in use,
> +and should always be specified as
> +.IR sizeof(struct file_attr) .
> +.P
> +The
> +.I flags
> +argument contains a bitwise OR of zero or more of the following constants:
> +.TP
> +.B AT_EMPTY_PATH
> +If
> +.I path
> +is an empty string,
> +operate on the file referred to by
> +.IR dirfd .
> +In this case,
> +.I dirfd
> +can refer to any type of file,
> +not just a directory.
> +.TP
> +.B AT_SYMLINK_NOFOLLOW
> +If
> +.I path
> +is a symbolic link,
> +do not dereference it;
> +instead,
> +get attributes of the symbolic link inode itself.
> +.SH RETURN VALUE
> +On success,
> +zero is returned.
> +On error,
> +\-1 is returned,
> +and
> +.I errno
> +is set to indicate the error.
> +.SH ERRORS
> +.TP
> +.B E2BIG
> +.I size
> +is too big (larger than
> +.BR PAGE_SIZE ).
> +.TP
> +.B EACCES
> +Search permission is denied for one of the directories
> +in the path prefix of
> +.IR path .
> +.TP
> +.B EBADF
> +.I path
> +is relative but
> +.I dirfd
> +is neither
> +.B AT_FDCWD
> +nor a valid file descriptor.
> +.TP
> +.B EBADF
> +.I path
> +is an empty string,
> +.B AT_EMPTY_PATH
> +was specified,
> +but
> +.I dirfd
> +is neither
> +.B AT_FDCWD
> +nor a valid file descriptor.
> +.TP
> +.B EFAULT
> +.I path
> +or
> +.I fattr
> +is an invalid pointer.
> +.TP
> +.B EINVAL
> +Unknown flags specified in
> +.IR flags .
> +.TP
> +.B EINVAL
> +.I size
> +is smaller than
> +.BR FILE_ATTR_SIZE_VER0 .
> +.TP
> +.B ELOOP
> +Too many symbolic links encountered while resolving
> +.IR path .
> +.TP
> +.B ENAMETOOLONG
> +.I path
> +is too long.
> +.TP
> +.B ENOENT
> +A component of
> +.I path
> +does not exist.
> +.TP
> +.B ENOENT
> +.I path
> +is an empty string and
> +.B AT_EMPTY_PATH
> +was not specified in
> +.IR flags .
> +.TP
> +.B ENOMEM
> +Insufficient kernel memory was available.
> +.TP
> +.B ENOTDIR
> +A component of the path prefix of
> +.I path
> +is not a directory.
> +.TP
> +.B ENOTDIR
> +.I path
> +is relative and
> +.I dirfd
> +is a file descriptor referring to a file other than a directory.
> +.TP
> +.B EOPNOTSUPP
> +The filesystem does not support getting attributes on this type of inode.
> +.SH HISTORY
> +Linux 6.17
> +.SH NOTES
> +This system call is designed to be extensible.
> +The
> +.I size
> +argument allows user-space applications to indicate
> +which version of the
> +.I file_attr
> +structure they are using,
> +enabling the kernel to support both old and new versions
> +of the structure simultaneously.
> +.P
> +If
> +.I size
> +is smaller than the structure size the kernel expects,
> +only the fields that fit within
> +.I size
> +will be filled in.
> +If
> +.I size
> +is larger than the kernel's structure size,
> +the extra bytes are zeroed.
> +.SH EXAMPLES
> +The program below demonstrates the use of
> +.BR file_getattr ()
> +to retrieve and display file attributes.
> +.P
> +.in +4n
> +.\" SRC BEGIN (file_getattr.c)
> +.EX
> +#define _GNU_SOURCE
> +#include <fcntl.h>
> +#include <linux/fs.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <sys/syscall.h>
> +#include <unistd.h>
> +\&
> +#ifndef SYS_file_getattr
> +#define SYS_file_getattr 467
> +#endif
> +\&
> +int
> +main(int argc, char *argv[])
> +{
> +    struct file_attr fa;
> +    long ret;
> +\&
> +    if (argc != 2) {
> +        fprintf(stderr, "Usage: %s <filename>\[rs]n", argv[0]);
> +        exit(EXIT_FAILURE);
> +    }
> +\&
> +    ret = syscall(SYS_file_getattr, AT_FDCWD, argv[1], &fa,
> +                  sizeof(fa), 0);
> +    if (ret == \-1) {
> +        perror("file_getattr");
> +        exit(EXIT_FAILURE);
> +    }
> +\&
> +    printf("File attributes:\[rs]n");
> +    printf("  xflags:     0x%w64x\[rs]n", fa.fa_xflags);
> +    printf("  extsize:    %w32u\[rs]n", fa.fa_extsize);
> +    printf("  nextents:   %w32u\[rs]n", fa.fa_nextents);
> +    printf("  projid:     %w32u\[rs]n", fa.fa_projid);
> +    printf("  cowextsize: %w32u\[rs]n", fa.fa_cowextsize);
> +\&
> +    /*
> +     * Try setting NODUMP flag with chattr +d ./foo to see
> +     * the difference.
> +     */
> +    if (fa.fa_xflags & FS_XFLAG_NODUMP)
> +        printf("  NODUMP flag is set\[rs]n");
> +\&
> +    exit(EXIT_SUCCESS);
> +}
> +.EE
> +.\" SRC END
> +.in
> +.SH SEE ALSO
> +.BR file_setattr (2),
> +.BR file_attr (2type),
> +.BR ioctl (2),
> +.BR ioctl_fs (2),
> +.BR openat (2),
> +.BR ioctl_xfs_fssetxattr (2)
> -- 
> 2.56.0
> 
> 

-- 
<https://www.alejandro-colomar.es>

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