[PATCH 01/20] vfs: Add file timestamp range support

[Deepa Dinamani <deepa.kernel@gmail.com>]

Add fields to the superblock to track the min and max
timestamps supported by filesystems.

Initially, when a superblock is allocated, initialize
it to the max and min values the fields can hold.
Individual filesystems override these to match their
actual limits.

Pseudo filesystems are assumed to always support the
min and max allowable values for the fields.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
---
 fs/super.c             | 2 ++
 include/linux/fs.h     | 3 +++
 include/linux/time64.h | 2 ++
 3 files changed, 7 insertions(+)

diff --git a/fs/super.c b/fs/super.c
index 2739f57515f8..e5835c38d336 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -257,6 +257,8 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
 	s->s_maxbytes = MAX_NON_LFS;
 	s->s_op = &default_op;
 	s->s_time_gran = 1000000000;
+	s->s_time_min = TIME64_MIN;
+	s->s_time_max = TIME64_MAX;
 	s->cleancache_poolid = CLEANCACHE_NO_POOL;
 
 	s->s_shrink.seeks = DEFAULT_SEEKS;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f1a6ca872943..e9d04e4e5628 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1448,6 +1448,9 @@ struct super_block {
 
 	/* Granularity of c/m/atime in ns (cannot be worse than a second) */
 	u32			s_time_gran;
+	/* Time limits for c/m/atime in seconds */
+	time64_t		   s_time_min;
+	time64_t		   s_time_max;
 #ifdef CONFIG_FSNOTIFY
 	__u32			s_fsnotify_mask;
 	struct fsnotify_mark_connector __rcu	*s_fsnotify_marks;
diff --git a/include/linux/time64.h b/include/linux/time64.h
index a620ee610b9f..19125489ae94 100644
--- a/include/linux/time64.h
+++ b/include/linux/time64.h
@@ -30,6 +30,8 @@ struct itimerspec64 {
 
 /* Located here for timespec[64]_valid_strict */
 #define TIME64_MAX			((s64)~((u64)1 << 63))
+#define TIME64_MIN			(-TIME64_MAX - 1)
+
 #define KTIME_MAX			((s64)~((u64)1 << 63))
 #define KTIME_SEC_MAX			(KTIME_MAX / NSEC_PER_SEC)
 
-- 
2.17.1