[PATCH 7/8] xfs_io: fix pwrite/pread length truncation on 32-bit systems

Darrick J. Wong
2020-01-24T00:17:23Z

From: Darrick J. Wong <darrick.wong@oracle.com>

The pwrite and pread commands in xfs_io accept an operation length that
can be any quantity that fits in a long long int; and loops to handle
the cases where the operation length is larger than the IO buffer.

Weirdly, the do_ functions contain code to shorten the operation to the
IO buffer size but the @count parameter is size_t, which means that for
a large argument on a 32-bit system, we rip off the upper bits of the
length, turning your 8GB write into a 0 byte write, which does nothing.

This was found by running generic/175 and observing that the 8G test
file it creates has zero length after the operation:

wrote 0/8589934592 bytes at offset 0
0.000000 bytes, 0 ops; 0.0001 sec (0.000000 bytes/sec and 0.0000 ops/sec)

Fix this by pushing long long count all the way through the call stack.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
io/pread.c | 4 ++--
io/pwrite.c | 6 +++---
2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/io/pread.c b/io/pread.c
index 1b4352be..d52e21d9 100644
--- a/io/pread.c
+++ b/io/pread.c
@@ -164,7 +164,7 @@ static ssize_t
do_preadv(
int fd,
off64_t offset,
- size_t count)
+ long long count)
{
int vecs = 0;
ssize_t oldlen = 0;
@@ -199,7 +199,7 @@ static ssize_t
do_pread(
int fd,
off64_t offset,
- size_t count,
+ long long count,
size_t buffer_size)
{
if (!vectors)
diff --git a/io/pwrite.c b/io/pwrite.c
index ccf14be9..1c28612f 100644
--- a/io/pwrite.c
+++ b/io/pwrite.c
@@ -54,8 +54,8 @@ static ssize_t
do_pwritev(
int fd,
off64_t offset,
- size_t count,
- int pwritev2_flags)
+ long long count,
+ int pwritev2_flags)
{
int vecs = 0;
ssize_t oldlen = 0;
@@ -97,7 +97,7 @@ static ssize_t
do_pwrite(
int fd,
off64_t offset,
- size_t count,
+ long long count,
size_t buffer_size,
int pwritev2_flags)
{