https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=293489
Bug ID: 293489
Summary: readv(2) on cuse device never returns
Product: Base System
Version: 15.0-RELEASE
Hardware: amd64
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: bin
Assignee: [email protected]
Reporter: [email protected]
Issuing a read(2) on a cuse device that has data to returns works as expected.
When switching to readv(2) with eight iovec-s, the readv call never returns.
Logging from an instrumented cuse device shows the first read is passed the
correct buffer address and size. The data appears to be transferred. All
subsequent read requires processed inside the cuse device have a correct buffer
address but the length is zero.
Code snippet follows:
#include <unistd.h>
#include <sys/uio.h>
int okay;
char chunk[8];
struct iovec list[8] =
{
{chunk + 0, 1},
{chunk + 1, 1},
{chunk + 2, 1},
{chunk + 3, 1},
{chunk + 4, 1},
{chunk + 5, 1},
{chunk + 6, 1},
{chunk + 7, 1}
};
int handle = open(/dev/cuse123", O_RDONLY);
do
{
okay = readv(handle, list, 8);
if (okay < 0) break;
write(2, chunk, okay);
}
while (true);
close(handle);
Switching back to a simple read(2) call works as expected.
The underlying issue is likely inside the cuse kernel module but this is just a
guess.
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