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Message-Id: <20180619153822.3638475-1-arnd@arndb.de>
Date: Tue, 19 Jun 2018 17:37:35 +0200
From: Arnd Bergmann <arnd@...db.de>
To: Jan Harkes <jaharkes@...cmu.edu>, coda@...cmu.edu
Cc: y2038@...ts.linaro.org, Arnd Bergmann <arnd@...db.de>,
Jonathan Corbet <corbet@....net>,
Deepa Dinamani <deepa.kernel@...il.com>,
codalist@...a.cs.cmu.edu, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH] 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.
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
Documentation/filesystems/coda.txt | 11 ++++++---
fs/coda/coda_linux.c | 50 +++++++++++++++++++++++++++++---------
include/uapi/linux/coda.h | 20 ++++++++++++---
3 files changed, 62 insertions(+), 19 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 */
diff --git a/fs/coda/coda_linux.c b/fs/coda/coda_linux.c
index f3d543dd9a98..8addcd166908 100644
--- a/fs/coda/coda_linux.c
+++ b/fs/coda/coda_linux.c
@@ -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)
@@ -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);
}
@@ -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;
@@ -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);
}
}
diff --git a/include/uapi/linux/coda.h b/include/uapi/linux/coda.h
index 695fade33c64..027a8eb04423 100644
--- a/include/uapi/linux/coda.h
+++ b/include/uapi/linux/coda.h
@@ -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 */
--
2.9.0
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