[PATCH] man: document that XFS_IOC_FS[G|S]ETXATTR can not be used on special files

[Andrey Albershteyn <aalbersh@kernel.org>]

Add a CAVEATS section with an note that these ioctls can not be used on
special files and leave a reference to an alternative pathname based
syscall interface.

Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>
---
 man/man2/ioctl_xfs_fsgetxattr.2 | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/man/man2/ioctl_xfs_fsgetxattr.2 b/man/man2/ioctl_xfs_fsgetxattr.2
index 25a9ba7965d1..5d223138e419 100644
--- a/man/man2/ioctl_xfs_fsgetxattr.2
+++ b/man/man2/ioctl_xfs_fsgetxattr.2
@@ -238,6 +238,23 @@ Caller did not have permission to change the attributes.
 This API is implemented by the ext4, xfs, btrfs, and f2fs filesystems on the
 Linux kernel.
 Not all fields may be understood by filesystems other than xfs.
+.SH CAVEATS
+The
+.B XFS_IOC_FSGETXATTR
+and
+.B XFS_IOC_FSSETXATTR
+.BR ioctl (2)
+operations require the user to open the file, but this may not be possible or
+lead to side effects on special files such as FIFOs, sockets, block devices,
+character devices, and symlinks.
+.P
+For a pathname based interface see
+.BR file_getattr (2)
+and
+.BR file_setattr (2)
+syscalls.
 .SH SEE ALSO
 .BR ioctl (2),
-.BR ioctl_iflags (2)
+.BR ioctl_iflags (2),
+.BR file_getattr (2),
+.BR file_setattr (2)
-- 
2.55.0