linux-kernel - [PATCH 1/2] [v2] afs: stop using time

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Message-Id: <20180620140256.19648-1-arnd@arndb.de>
Date:   Wed, 20 Jun 2018 16:02:47 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     David Howells <dhowells@...hat.com>
Cc:     y2038@...ts.linaro.org, Arnd Bergmann <arnd@...db.de>,
        linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] [v2] afs: stop using time_t for internal times

afs uses 32-bit timestamps everywhere, but mixes signed and unsigned
usage, which is a bit inconsistent. In particular on 32-bit machines,
it currently uses unsigned timestamps (ranging from 1970 to 2106) for
locally modified files, but signed timestamps (rand 1902 to 2038) when
reading from a remote end. On 64-bit machines, we always interpret
timestamps as unsigned here.

This replaces the deprecated time_t with a new explicitly unsigned
afs_time32_t to get a consistent interpretation of inode times
according the the wire protocol definition.

This avoids the y2038 overflow on 32-bit machines, extending the range
to the end of the afs_time32_t in year 2106. On 64-bit machines, using
the shorter type saves a few bytes for each afs_file_status and
afs_volsync saves a few bytes over time_t or time64_t.

Note that mtime_server and struct afs_volsync are not currently
used in any meaningful way and could be removed completely.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 fs/afs/afs.h | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/afs/afs.h b/fs/afs/afs.h
index b4ff1f7ae4ab..a17f4ce06323 100644
--- a/fs/afs/afs.h
+++ b/fs/afs/afs.h
@@ -26,6 +26,7 @@
 typedef unsigned			afs_volid_t;
 typedef unsigned			afs_vnodeid_t;
 typedef unsigned long long		afs_dataversion_t;
+typedef unsigned			afs_time32_t;

 typedef enum {
 	AFSVL_RWVOL,			/* read/write volume */
@@ -129,8 +130,8 @@ typedef u32 afs_access_t;
 struct afs_file_status {
 	u64			size;		/* file size */
 	afs_dataversion_t	data_version;	/* current data version */
-	time_t			mtime_client;	/* last time client changed data */
-	time_t			mtime_server;	/* last time server changed data */
+	afs_time32_t		mtime_client;	/* last time client changed data */
+	afs_time32_t		mtime_server;	/* last time server changed data */
 	unsigned		abort_code;	/* Abort if bulk-fetching this failed */

 	afs_file_type_t		type;		/* file type */
@@ -158,7 +159,7 @@ struct afs_file_status {
  * AFS volume synchronisation information
  */
 struct afs_volsync {
-	time_t			creation;	/* volume creation time */
+	afs_time32_t		creation;	/* volume creation time */
 };

 /*
-- 
2.9.0