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authorArnd Bergmann <arnd@arndb.de>2019-07-17 02:28:32 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-17 05:23:23 +0300
commit6ced9aa7b56baeb241a715df4539e60d5e3118e2 (patch)
treec4dee6c280f6222228737302d2cd1528100b78f0 /Documentation/filesystems
parent850622136ff2a1296b2c8aa5280a74a6a3aabe4e (diff)
downloadlinux-6ced9aa7b56baeb241a715df4539e60d5e3118e2.tar.xz
coda: stop using 'struct timespec' in user API
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>
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/coda.txt11
1 files changed, 7 insertions, 4 deletions
diff --git a/Documentation/filesystems/coda.txt b/Documentation/filesystems/coda.txt
index 61311356025d..ea5969068895 100644
--- a/Documentation/filesystems/coda.txt
+++ b/Documentation/filesystems/coda.txt
@@ -481,7 +481,10 @@ kernel support.
-
+ struct vtimespec {
+ long tv_sec; /* seconds */
+ long tv_nsec; /* nanoseconds */
+ };
struct coda_vattr {
enum coda_vtype va_type; /* vnode type (for create) */
@@ -493,9 +496,9 @@ kernel support.
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 */
dev_t va_rdev; /* device special file represents */