Skip to content

Commit

Permalink
coda: stop using 'struct timespec' in user API
Browse files Browse the repository at this point in the history 
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 <[email protected]>
Signed-off-by: Jan Harkes <[email protected]>
Acked-by: Jan Harkes <[email protected]>
Cc: Colin Ian King <[email protected]>
Cc: Dan Carpenter <[email protected]>
Cc: David Howells <[email protected]>
Cc: Fabian Frederick <[email protected]>
Cc: Mikko Rapeli <[email protected]>
Cc: Sam Protsenko <[email protected]>
Cc: Yann Droneaud <[email protected]>
Cc: Zhouyang Jia <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
  • Loading branch information
@arndb @torvalds
arndb authored and torvalds committed Jul 17, 2019
1 parent 8506221 commit 6ced9aa
Show file tree
Hide file tree
Showing 3 changed files with 62 additions and 19 deletions.
11 changes: 7 additions & 4 deletions Documentation/filesystems/coda.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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) */
Expand All @@ -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 */
Expand Down
50 changes: 38 additions & 12 deletions fs/coda/coda_linux.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,32 @@ unsigned short coda_flags_to_cflags(unsigned short flags)
return coda_flags;
}

static struct timespec64 coda_to_timespec64(struct vtimespec ts)
{
/*
* We interpret incoming timestamps as 'signed' to match traditional
* usage and support pre-1970 timestamps, but this breaks in y2038
* on 32-bit machines.
*/
struct timespec64 ts64 = {
.tv_sec = ts.tv_sec,
.tv_nsec = ts.tv_nsec,
};

return ts64;
}

static struct vtimespec timespec64_to_coda(struct timespec64 ts64)
{
/* clamp the timestamps to the maximum range rather than wrapping */
struct vtimespec ts = {
.tv_sec = lower_32_bits(clamp_t(time64_t, ts64.tv_sec,
LONG_MIN, LONG_MAX)),
.tv_nsec = ts64.tv_nsec,
};

return ts;
}

/* utility functions below */
void coda_vattr_to_iattr(struct inode *inode, struct coda_vattr *attr)
Expand Down Expand Up @@ -105,11 +131,11 @@ void coda_vattr_to_iattr(struct inode *inode, struct coda_vattr *attr)
if (attr->va_size != -1)
inode->i_blocks = (attr->va_size + 511) >> 9;
if (attr->va_atime.tv_sec != -1)
inode->i_atime = timespec_to_timespec64(attr->va_atime);
inode->i_atime = coda_to_timespec64(attr->va_atime);
if (attr->va_mtime.tv_sec != -1)
inode->i_mtime = timespec_to_timespec64(attr->va_mtime);
inode->i_mtime = coda_to_timespec64(attr->va_mtime);
if (attr->va_ctime.tv_sec != -1)
inode->i_ctime = timespec_to_timespec64(attr->va_ctime);
inode->i_ctime = coda_to_timespec64(attr->va_ctime);
}


Expand All @@ -130,12 +156,12 @@ void coda_iattr_to_vattr(struct iattr *iattr, struct coda_vattr *vattr)
vattr->va_uid = (vuid_t) -1;
vattr->va_gid = (vgid_t) -1;
vattr->va_size = (off_t) -1;
vattr->va_atime.tv_sec = (time_t) -1;
vattr->va_atime.tv_nsec = (time_t) -1;
vattr->va_mtime.tv_sec = (time_t) -1;
vattr->va_mtime.tv_nsec = (time_t) -1;
vattr->va_ctime.tv_sec = (time_t) -1;
vattr->va_ctime.tv_nsec = (time_t) -1;
vattr->va_atime.tv_sec = (long) -1;
vattr->va_atime.tv_nsec = (long) -1;
vattr->va_mtime.tv_sec = (long) -1;
vattr->va_mtime.tv_nsec = (long) -1;
vattr->va_ctime.tv_sec = (long) -1;
vattr->va_ctime.tv_nsec = (long) -1;
vattr->va_type = C_VNON;
vattr->va_fileid = -1;
vattr->va_gen = -1;
Expand Down Expand Up @@ -175,13 +201,13 @@ void coda_iattr_to_vattr(struct iattr *iattr, struct coda_vattr *vattr)
vattr->va_size = iattr->ia_size;
}
if ( valid & ATTR_ATIME ) {
vattr->va_atime = timespec64_to_timespec(iattr->ia_atime);
vattr->va_atime = timespec64_to_coda(iattr->ia_atime);
}
if ( valid & ATTR_MTIME ) {
vattr->va_mtime = timespec64_to_timespec(iattr->ia_mtime);
vattr->va_mtime = timespec64_to_coda(iattr->ia_mtime);
}
if ( valid & ATTR_CTIME ) {
vattr->va_ctime = timespec64_to_timespec(iattr->ia_ctime);
vattr->va_ctime = timespec64_to_coda(iattr->ia_ctime);
}
}

20 changes: 17 additions & 3 deletions include/uapi/linux/coda.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand All @@ -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 */
Expand Down

0 comments on commit 6ced9aa

Please sign in to comment.