staging/lustre/lov: remove set_fs() call from lov_getstripe()

commit 0a33252e upstream.

lov_getstripe() calls set_fs(KERNEL_DS) so that it can handle a struct
lov_user_md pointer from user- or kernel-space.  This changes the
behavior of copy_from_user() on SPARC and may result in a misaligned
access exception which in turn oopses the kernel.  In fact the
relevant argument to lov_getstripe() is never called with a
kernel-space pointer and so changing the address limits is unnecessary
and so we remove the calls to save, set, and restore the address
limits.
Signed-off-by: John L. Hammond <john.hammond@intel.com>
Reviewed-on: http://review.whamcloud.com/6150
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3221Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Li Wei <wei.g.li@intel.com>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/staging/lustre/lustre/lov/lov_pack.c

@@ -592,18 +592,10 @@ int lov_getstripe(struct obd_export *exp, struct lov_stripe_md *lsm,
 	struct lov_mds_md *lmmk = NULL;
 	int rc, lmm_size;
 	int lum_size;
-	mm_segment_t seg;
 
 	if (!lsm)
 		return -ENODATA;
 
-	/*
-	 * "Switch to kernel segment" to allow copying from kernel space by
-	 * copy_{to,from}_user().
-	 */
-	seg = get_fs();
-	set_fs(KERNEL_DS);
-
 	/* we only need the header part from user space to get lmm_magic and
 	 * lmm_stripe_count, (the header part is common to v1 and v3) */
 	lum_size = sizeof(struct lov_user_md_v1);
@@ -672,6 +664,5 @@ int lov_getstripe(struct obd_export *exp, struct lov_stripe_md *lsm,
 
 	obd_free_diskmd(exp, &lmmk);
 out_set:
-	set_fs(seg);
 	return rc;
 }