[v8,08/20] adfs: Fill in max and min timestamps in sb
diff mbox series

Message ID 20190818165817.32634-9-deepa.kernel@gmail.com
State New
Headers show
Series
  • vfs: Add support for timestamp limits
Related show

Commit Message

Deepa Dinamani Aug. 18, 2019, 4:58 p.m. UTC
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@gmail.com>
---
 fs/adfs/adfs.h  | 13 +++++++++++++
 fs/adfs/inode.c |  8 ++------
 fs/adfs/super.c |  2 ++
 3 files changed, 17 insertions(+), 6 deletions(-)

Comments

Matthew Wilcox Aug. 20, 2019, 4:28 p.m. UTC | #1
On Sun, Aug 18, 2019 at 09:58:05AM -0700, Deepa Dinamani wrote:
> 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().

That's not actually correct.  RISC OS timestamps are centiseconds since
1900 stored in 5 bytes.

> Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
> ---
>  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
>
Deepa Dinamani Aug. 20, 2019, 11:55 p.m. UTC | #2
On Tue, Aug 20, 2019 at 9:28 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Sun, Aug 18, 2019 at 09:58:05AM -0700, Deepa Dinamani wrote:
> > 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().
>
> That's not actually correct.  RISC OS timestamps are centiseconds since
> 1900 stored in 5 bytes.

The timestamp can hold earlier values but the fs implementation
explicitly rejects those in adfs_adfs2unix_time() too_early check.
We could fix the implementation to not throw away times before 1970.
Are you suggesting we want to do this?
I could post a separate patch to fix this or we could do it as part of
the series.

 static void
 adfs_adfs2unix_time(struct timespec64 *tv, struct inode *inode)
 {
         unsigned int high, low;
         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))
                 goto cur_time;

         high = ADFS_I(inode)->loadaddr & 0xFF; /* top 8 bits of timestamp */
         low  = ADFS_I(inode)->execaddr;    /* bottom 32 bits of timestamp */

         /* convert 40-bit centi-seconds to 32-bit seconds
          * going via nanoseconds to retain precision
          */
         nsec = (((s64) high << 32) | (s64) low) * 10000000; /* cs to ns */

         /* Files dated pre  01 Jan 1970 00:00:00. */
         if (nsec < nsec_unix_epoch_diff_risc_os_epoch)
                 goto too_early;

         /* convert from RISC OS to Unix epoch */
         nsec -= nsec_unix_epoch_diff_risc_os_epoch;

         *tv = ns_to_timespec64(nsec);
         return;

  cur_time:
         *tv = current_time(inode);
         return;

  too_early:
         tv->tv_sec = tv->tv_nsec = 0;
         return;
 }

-Deepa

Patch
diff mbox series

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)) {