[PATCH v8 08/20] adfs: Fill in max and min timestamps in sb

[Deepa Dinamani <deepa.kernel@xxxxxxxxx>]

Fill in the appropriate limits to avoid inconsistencies
in the vfs cached inode times when timestamps are
outside the permitted range.

Note that the min timestamp is assumed to be
01 Jan 1970 00:00:00 (Unix epoch). This is consistent
with the way we convert timestamps in adfs_adfs2unix_time().

Signed-off-by: Deepa Dinamani <deepa.kernel@xxxxxxxxx>
---
 fs/adfs/adfs.h  | 13 +++++++++++++
 fs/adfs/inode.c |  8 ++------
 fs/adfs/super.c |  2 ++
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/fs/adfs/adfs.h b/fs/adfs/adfs.h
index b7e844d2f321..dca8b23aa43f 100644
--- a/fs/adfs/adfs.h
+++ b/fs/adfs/adfs.h
@@ -3,6 +3,19 @@
 #include <linux/fs.h>
 #include <linux/adfs_fs.h>
 
+/*
+ * 01 Jan 1970 00:00:00 (Unix epoch) as seconds since
+ * 01 Jan 1900 00:00:00 (RISC OS epoch)
+ */
+#define RISC_OS_EPOCH_DELTA 2208988800LL
+
+/*
+ * Convert 40 bit centi seconds to seconds
+ * since 01 Jan 1900 00:00:00 (RISC OS epoch)
+ * The result is 2248-06-03 06:57:57 GMT
+ */
+#define ADFS_MAX_TIMESTAMP ((0xFFFFFFFFFFLL / 100) - RISC_OS_EPOCH_DELTA)
+
 /* Internal data structures for ADFS */
 
 #define ADFS_FREE_FRAG		 0
diff --git a/fs/adfs/inode.c b/fs/adfs/inode.c
index 124de75413a5..41eca1c451dc 100644
--- a/fs/adfs/inode.c
+++ b/fs/adfs/inode.c
@@ -167,11 +167,7 @@ static void
 adfs_adfs2unix_time(struct timespec64 *tv, struct inode *inode)
 {
 	unsigned int high, low;
-	/* 01 Jan 1970 00:00:00 (Unix epoch) as nanoseconds since
-	 * 01 Jan 1900 00:00:00 (RISC OS epoch)
-	 */
-	static const s64 nsec_unix_epoch_diff_risc_os_epoch =
-							2208988800000000000LL;
+	static const s64 nsec_unix_epoch_diff_risc_os_epoch = RISC_OS_EPOCH_DELTA * NSEC_PER_SEC;
 	s64 nsec;
 
 	if (!adfs_inode_is_stamped(inode))
@@ -216,7 +212,7 @@ adfs_unix2adfs_time(struct inode *inode, unsigned int secs)
 	if (adfs_inode_is_stamped(inode)) {
 		/* convert 32-bit seconds to 40-bit centi-seconds */
 		low  = (secs & 255) * 100;
-		high = (secs / 256) * 100 + (low >> 8) + 0x336e996a;
+		high = (secs / 256) * 100 + (low >> 8) + (RISC_OS_EPOCH_DELTA*100/256);
 
 		ADFS_I(inode)->loadaddr = (high >> 24) |
 				(ADFS_I(inode)->loadaddr & ~0xff);
diff --git a/fs/adfs/super.c b/fs/adfs/super.c
index 65b04ebb51c3..f074fe7d7158 100644
--- a/fs/adfs/super.c
+++ b/fs/adfs/super.c
@@ -463,6 +463,8 @@ static int adfs_fill_super(struct super_block *sb, void *data, int silent)
 	asb->s_map_size		= dr->nzones | (dr->nzones_high << 8);
 	asb->s_map2blk		= dr->log2bpmb - dr->log2secsize;
 	asb->s_log2sharesize	= dr->log2sharesize;
+	sb->s_time_min		= 0;
+	sb->s_time_max		= ADFS_MAX_TIMESTAMP;
 
 	asb->s_map = adfs_read_map(sb, dr);
 	if (IS_ERR(asb->s_map)) {
-- 
2.17.1