ocfs2: dlmglue: clean up timestamp handling

The handling of timestamps outside of the 1970..2038 range in the dlm
glue is rather inconsistent: on 32-bit architectures, this has always
wrapped around to negative timestamps in the 1902..1969 range, while on
64-bit kernels all timestamps are interpreted as positive 34 bit numbers
in the 1970..2514 year range.

Now that the VFS code handles 64-bit timestamps on all architectures, we
can make the behavior more consistent here, and return the same result
that we had on 64-bit already, making the file system y2038 safe in the
process.  Outside of dlmglue, it already uses 64-bit on-disk timestamps
anway, so that part is fine.

For consistency, I'm changing ocfs2_pack_timespec() to clamp anything
outside of the supported range to the minimum and maximum values.  This
avoids a possible ambiguity of values before 1970 in particular, which
used to be interpreted as times at the end of the 2514 range previously.

Link: http://lkml.kernel.org/r/20180619155826.4106487-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <ge.changwei@h3c.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/dlmglue.c

@@ -2123,10 +2123,10 @@ static void ocfs2_downconvert_on_unlock(struct ocfs2_super *osb,
 
 /* LVB only has room for 64 bits of time here so we pack it for
  * now. */
-static u64 ocfs2_pack_timespec(struct timespec *spec)
+static u64 ocfs2_pack_timespec(struct timespec64 *spec)
 {
 	u64 res;
-	u64 sec = spec->tv_sec;
+	u64 sec = clamp_t(time64_t, spec->tv_sec, 0, 0x3ffffffffull);
 	u32 nsec = spec->tv_nsec;
 
 	res = (sec << OCFS2_SEC_SHIFT) | (nsec & OCFS2_NSEC_MASK);
@@ -2142,7 +2142,6 @@ static void __ocfs2_stuff_meta_lvb(struct inode *inode)
 	struct ocfs2_inode_info *oi = OCFS2_I(inode);
 	struct ocfs2_lock_res *lockres = &oi->ip_inode_lockres;
 	struct ocfs2_meta_lvb *lvb;
-	struct timespec ts;
 
 	lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
 
@@ -2163,15 +2162,12 @@ static void __ocfs2_stuff_meta_lvb(struct inode *inode)
 	lvb->lvb_igid      = cpu_to_be32(i_gid_read(inode));
 	lvb->lvb_imode     = cpu_to_be16(inode->i_mode);
 	lvb->lvb_inlink    = cpu_to_be16(inode->i_nlink);
-	ts = timespec64_to_timespec(inode->i_atime);
 	lvb->lvb_iatime_packed  =
-		cpu_to_be64(ocfs2_pack_timespec(&ts));
-	ts = timespec64_to_timespec(inode->i_ctime);
+		cpu_to_be64(ocfs2_pack_timespec(&inode->i_atime));
 	lvb->lvb_ictime_packed =
-		cpu_to_be64(ocfs2_pack_timespec(&ts));
-	ts = timespec64_to_timespec(inode->i_mtime);
+		cpu_to_be64(ocfs2_pack_timespec(&inode->i_ctime));
 	lvb->lvb_imtime_packed =
-		cpu_to_be64(ocfs2_pack_timespec(&ts));
+		cpu_to_be64(ocfs2_pack_timespec(&inode->i_mtime));
 	lvb->lvb_iattr    = cpu_to_be32(oi->ip_attr);
 	lvb->lvb_idynfeatures = cpu_to_be16(oi->ip_dyn_features);
 	lvb->lvb_igeneration = cpu_to_be32(inode->i_generation);
@@ -2180,7 +2176,7 @@ out:
 	mlog_meta_lvb(0, lockres);
 }
 
-static void ocfs2_unpack_timespec(struct timespec *spec,
+static void ocfs2_unpack_timespec(struct timespec64 *spec,
 				  u64 packed_time)
 {
 	spec->tv_sec = packed_time >> OCFS2_SEC_SHIFT;
@@ -2189,7 +2185,6 @@ static void ocfs2_unpack_timespec(struct timespec *spec,
 
 static void ocfs2_refresh_inode_from_lvb(struct inode *inode)
 {
-	struct timespec ts;
 	struct ocfs2_inode_info *oi = OCFS2_I(inode);
 	struct ocfs2_lock_res *lockres = &oi->ip_inode_lockres;
 	struct ocfs2_meta_lvb *lvb;
@@ -2217,15 +2212,12 @@ static void ocfs2_refresh_inode_from_lvb(struct inode *inode)
 	i_gid_write(inode, be32_to_cpu(lvb->lvb_igid));
 	inode->i_mode    = be16_to_cpu(lvb->lvb_imode);
 	set_nlink(inode, be16_to_cpu(lvb->lvb_inlink));
-	ocfs2_unpack_timespec(&ts,
+	ocfs2_unpack_timespec(&inode->i_atime,
 			      be64_to_cpu(lvb->lvb_iatime_packed));
-	inode->i_atime = timespec_to_timespec64(ts);
-	ocfs2_unpack_timespec(&ts,
+	ocfs2_unpack_timespec(&inode->i_mtime,
 			      be64_to_cpu(lvb->lvb_imtime_packed));
-	inode->i_mtime = timespec_to_timespec64(ts);
-	ocfs2_unpack_timespec(&ts,
+	ocfs2_unpack_timespec(&inode->i_ctime,
 			      be64_to_cpu(lvb->lvb_ictime_packed));
-	inode->i_ctime = timespec_to_timespec64(ts);
 	spin_unlock(&oi->ip_lock);
 }