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coda: stop using 'struct timespec' in user API

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We exchange file timestamps with user space using psdev device
read/write operations with a fixed but architecture specific binary
layout.

On 32-bit systems, this uses a 'timespec' structure that is defined by
the C library to contain two 32-bit values for seconds and nanoseconds.
As we get ready for the year 2038 overflow of the 32-bit signed seconds,
the kernel now uses 64-bit timestamps internally, and user space will do
the same change by changing the 'timespec' definition in the future.

Unfortunately, this breaks the layout of the coda_vattr structure, so we
need to redefine that in terms of something that does not change.  I'm
introducing a new 'struct vtimespec' structure here that keeps the
existing layout, and the same change has to be done in the coda user
space copy of linux/coda.h before anyone can use that on a 32-bit
architecture with 64-bit time_t.

An open question is what should happen to actual times past y2038, as
they are now truncated to the last valid date when sent to user space,
and interpreted as pre-1970 times when a timestamp with the MSB set is
read back into the kernel.  Alternatively, we could change the new
timespec64_to_coda()/coda_to_timespec64() functions to use a different
interpretation and extend the available range further to the future by
disallowing past timestamps.  This would require more changes in the
user space side though.

Link: http://lkml.kernel.org/r/562b7324149461743e4fbe2fedbf7c242f7e274a.1558117389.git.jaharkes@cs.cmu.edu
Link: https://patchwork.kernel.org/patch/10474735/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jan Harkes <jaharkes@cs.cmu.edu>
Acked-by: Jan Harkes <jaharkes@cs.cmu.edu>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Mikko Rapeli <mikko.rapeli@iki.fi>
Cc: Sam Protsenko <semen.protsenko@linaro.org>
Cc: Yann Droneaud <ydroneaud@opteya.com>
Cc: Zhouyang Jia <jiazhouyang09@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Arnd Bergmann
2019-07-16 16:28:32 -07:00
committed by Linus Torvalds
parent 850622136f
commit 6ced9aa7b5
3 changed files with 62 additions and 19 deletions
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20
include/uapi/linux/coda.h
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@@ -211,6 +211,20 @@ struct CodaFid {
*/
enum coda_vtype { C_VNON, C_VREG, C_VDIR, C_VBLK, C_VCHR, C_VLNK, C_VSOCK, C_VFIFO, C_VBAD };
#ifdef __linux__
/*
* This matches the traditional Linux 'timespec' structure binary layout,
* before using 64-bit time_t everywhere. Overflows in y2038 on 32-bit
* architectures.
*/
struct vtimespec {
long tv_sec; /* seconds */
long tv_nsec; /* nanoseconds */
};
#else
#define vtimespec timespec
#endif
struct coda_vattr {
long va_type; /* vnode type (for create) */
u_short va_mode; /* files access mode and type */
@@ -220,9 +234,9 @@ struct coda_vattr {
long va_fileid; /* file id */
u_quad_t va_size; /* file size in bytes */
long va_blocksize; /* blocksize preferred for i/o */
struct timespec va_atime; /* time of last access */
struct timespec va_mtime; /* time of last modification */
struct timespec va_ctime; /* time file changed */
struct vtimespec va_atime; /* time of last access */
struct vtimespec va_mtime; /* time of last modification */
struct vtimespec va_ctime; /* time file changed */
u_long va_gen; /* generation number of file */
u_long va_flags; /* flags defined for file */
cdev_t va_rdev; /* device special file represents */