On 1/6/2024 20:33, Jens Axboe wrote:
On 6/1/24 9:51 AM, Stefan wrote:
On 1/6/2024 17:35, Jens Axboe wrote:
On 6/1/24 9:22 AM, Stefan wrote:
On 1/6/2024 17:05, Jens Axboe wrote:
On 6/1/24 8:19 AM, Jens Axboe wrote:
On 6/1/24 3:43 AM, Stefan wrote:
io_uring uses the __u32 len field in order to pass the length to
madvise and fadvise, but these calls use an off_t, which is 64bit on
64bit platforms.
When using liburing, the length is silently truncated to 32bits (so
8GB length would become zero, which has a different meaning of "until
the end of the file" for fadvise).
If my understanding is correct, we could fix this by introducing new
operations MADVISE64 and FADVISE64, which use the addr3 field instead
of the length field for length.
We probably just want to introduce a flag and ensure that older stable
kernels check it, and then use a 64-bit field for it when the flag is
set.
I think this should do it on the kernel side, as we already check these
fields and return -EINVAL as needed. Should also be trivial to backport.
Totally untested... Might want a FEAT flag for this, or something where
it's detectable, to make the liburing change straight forward.
diff --git a/io_uring/advise.c b/io_uring/advise.c
index 7085804c513c..cb7b881665e5 100644
--- a/io_uring/advise.c
+++ b/io_uring/advise.c
@@ -17,14 +17,14 @@
struct io_fadvise {
struct file *file;
u64 offset;
- u32 len;
+ u64 len;
u32 advice;
};
struct io_madvise {
struct file *file;
u64 addr;
- u32 len;
+ u64 len;
u32 advice;
};
@@ -33,11 +33,13 @@ int io_madvise_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
#if defined(CONFIG_ADVISE_SYSCALLS) && defined(CONFIG_MMU)
struct io_madvise *ma = io_kiocb_to_cmd(req, struct io_madvise);
- if (sqe->buf_index || sqe->off || sqe->splice_fd_in)
+ if (sqe->buf_index || sqe->splice_fd_in)
return -EINVAL;
ma->addr = READ_ONCE(sqe->addr);
- ma->len = READ_ONCE(sqe->len);
+ ma->len = READ_ONCE(sqe->off);
+ if (!ma->len)
+ ma->len = READ_ONCE(sqe->len);
ma->advice = READ_ONCE(sqe->fadvise_advice);
req->flags |= REQ_F_FORCE_ASYNC;
return 0;
@@ -78,11 +80,13 @@ int io_fadvise_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
struct io_fadvise *fa = io_kiocb_to_cmd(req, struct io_fadvise);
- if (sqe->buf_index || sqe->addr || sqe->splice_fd_in)
+ if (sqe->buf_index || sqe->splice_fd_in)
return -EINVAL;
fa->offset = READ_ONCE(sqe->off);
- fa->len = READ_ONCE(sqe->len);
+ fa->len = READ_ONCE(sqe->addr);
+ if (!fa->len)
+ fa->len = READ_ONCE(sqe->len);
fa->advice = READ_ONCE(sqe->fadvise_advice);
if (io_fadvise_force_async(fa))
req->flags |= REQ_F_FORCE_ASYNC;
If we want to have the length in the same field in both *ADVISE
operations, we can put a flag in splice_fd_in/optlen.
I don't think that part matters that much.
Maybe the explicit flag is a bit clearer for users of the API
compared to the implicit flag when setting sqe->len to zero?
We could go either way. The unused fields returning -EINVAL if set right
now can serve as the flag field - if you have it set, then that is your
length. If not, then the old style is the length. That's the approach I
took, rather than add an explicit flag to it. Existing users that would
set the 64-bit length fields would get -EINVAL already. And since the
normal flags field is already used for advice flags, I'd prefer just
using the existing 64-bit zero fields for it rather than add a flag in
an odd location. Would also make for an easier backport to stable.
But don't feel that strongly about that part.
Attached kernel patch with FEAT added, and liburing patch with 64
versions added.
Sounds good!
Do we want to do anything about the current (32-bit) functions in
liburing? They silently truncate the user's values, so either marking
them deprecated or changing the type of length in the arguments to a
__u32 could help.
I like changing it to an __u32, and then we'll add a note to the man
page for them as well (with references to the 64-bit variants).
I still need to write a test and actually test the patches, but I'll get
to that Monday. If you want to write a test case that checks the 64-bit
range, then please do!
Maybe something like the following for madvise?
Create an 8GB file initialized with 0xaa, punch a (8GB - page_size) hole
using MADV_REMOVE, and check the contents.
It requires support for FALLOC_FL_PUNCH_HOLE in the filesystem.
diff --git a/test/helpers.c b/test/helpers.c
index 779347f..acf1c7d 100644
--- a/test/helpers.c
+++ b/test/helpers.c
@@ -76,8 +76,9 @@ void *t_calloc(size_t nmemb, size_t size)
*/
static void __t_create_file(const char *file, size_t size, char pattern)
{
- ssize_t ret;
- char *buf;
+ ssize_t ret = 0;
+ size_t size_remaining;
+ char *buf, *buf_loc;
int fd;
buf = t_malloc(size);
@@ -86,11 +87,19 @@ static void __t_create_file(const char *file, size_t
size, char pattern)
fd = open(file, O_WRONLY | O_CREAT, 0644);
assert(fd >= 0);
- ret = write(fd, buf, size);
+ size_remaining = size;
+ buf_loc = buf;
+ while (size_remaining > 0) {
+ ret = write(fd, buf_loc, size_remaining);
+ if (ret <= 0)
+ break;
+ size_remaining -= ret;
+ buf_loc += ret;
+ }
fsync(fd);
close(fd);
free(buf);
- assert(ret == size);
+ assert(size_remaining == 0);
}
void t_create_file(const char *file, size_t size)
diff --git a/test/madvise.c b/test/madvise.c
index 7938ec4..b5b0cbe 100644
--- a/test/madvise.c
+++ b/test/madvise.c
@@ -15,34 +15,7 @@
#include "helpers.h"
#include "liburing.h"
-#define FILE_SIZE (128 * 1024)
-
-#define LOOPS 100
-#define MIN_LOOPS 10
-
-static unsigned long long utime_since(const struct timeval *s,
- const struct timeval *e)
-{
- long long sec, usec;
-
- sec = e->tv_sec - s->tv_sec;
- usec = (e->tv_usec - s->tv_usec);
- if (sec > 0 && usec < 0) {
- sec--;
- usec += 1000000;
- }
-
- sec *= 1000000;
- return sec + usec;
-}
-
-static unsigned long long utime_since_now(struct timeval *tv)
-{
- struct timeval end;
-
- gettimeofday(&end, NULL);
- return utime_since(tv, &end);
-}
+#define FILE_SIZE (8ULL * 1024ULL * 1024ULL * 1024ULL)
static int do_madvise(struct io_uring *ring, void *addr, off_t len,
int advice)
{
@@ -76,83 +49,62 @@ static int do_madvise(struct io_uring *ring, void
*addr, off_t len, int advice)
unlink(".madvise.tmp");
exit(0);
} else if (ret) {
- fprintf(stderr, "cqe->res=%d\n", cqe->res);
+ fprintf(stderr, "cqe->res=%d (%s)\n", cqe->res,
+ strerror(-cqe->res));
}
io_uring_cqe_seen(ring, cqe);
return ret;
}
-static long do_copy(int fd, char *buf, void *ptr)
-{
- struct timeval tv;
-
- gettimeofday(&tv, NULL);
- memcpy(buf, ptr, FILE_SIZE);
- return utime_since_now(&tv);
-}
-
static int test_madvise(struct io_uring *ring, const char *filename)
{
- unsigned long cached_read, uncached_read, cached_read2;
+ size_t page_size;
+ unsigned char contents;
int fd, ret;
- char *buf;
- void *ptr;
+ unsigned char *ptr;
+
+ page_size = sysconf(_SC_PAGE_SIZE);
- fd = open(filename, O_RDONLY);
+ fd = open(filename, O_RDWR);
if (fd < 0) {
perror("open");
return 1;
}
- buf = t_malloc(FILE_SIZE);
-
- ptr = mmap(NULL, FILE_SIZE, PROT_READ, MAP_PRIVATE, fd, 0);
+ ptr = mmap(NULL, FILE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (ptr == MAP_FAILED) {
perror("mmap");
return 1;
}
- cached_read = do_copy(fd, buf, ptr);
- if (cached_read == -1)
- return 1;
-
- cached_read = do_copy(fd, buf, ptr);
- if (cached_read == -1)
- return 1;
-
- ret = do_madvise(ring, ptr, FILE_SIZE, MADV_DONTNEED);
- if (ret)
- return 1;
-
- uncached_read = do_copy(fd, buf, ptr);
- if (uncached_read == -1)
- return 1;
-
- ret = do_madvise(ring, ptr, FILE_SIZE, MADV_DONTNEED);
- if (ret)
- return 1;
-
- ret = do_madvise(ring, ptr, FILE_SIZE, MADV_WILLNEED);
+ ret =
+ do_madvise(ring, ptr + page_size, FILE_SIZE - page_size,
+ MADV_REMOVE);
if (ret)
return 1;
- msync(ptr, FILE_SIZE, MS_SYNC);
-
- cached_read2 = do_copy(fd, buf, ptr);
- if (cached_read2 == -1)
- return 1;
-
- if (cached_read < uncached_read &&
- cached_read2 < uncached_read)
- return 0;
+ for (size_t i = 0; i < FILE_SIZE; i++) {
+ contents = ptr[i];
+ if (contents && i > page_size) {
+ fprintf(stderr,
+ "In removed page at %lu but contents=%x\n", i,
+ contents);
+ return 2;
+ } else if (contents != 0xaa && i < page_size) {
+ fprintf(stderr,
+ "In non-removed page at %lu but contents=%x\n",
+ i, contents);
+ return 2;
+ }
+ }
- return 2;
+ return 0;
}
int main(int argc, char *argv[])
{
struct io_uring ring;
- int ret, i, good, bad;
+ int ret;
char *fname;
if (argc > 1) {
@@ -167,23 +119,12 @@ int main(int argc, char *argv[])
goto err;
}
- good = bad = 0;
- for (i = 0; i < LOOPS; i++) {
- ret = test_madvise(&ring, fname);
- if (ret == 1) {
- fprintf(stderr, "test_madvise failed\n");
- goto err;
- } else if (!ret)
- good++;
- else if (ret == 2)
- bad++;
- if (i >= MIN_LOOPS && !bad)
- break;
+ ret = test_madvise(&ring, fname);
+ if (ret) {
+ fprintf(stderr, "test_madvise failed\n");
+ goto err;
}
- /* too hard to reliably test, just ignore */
- if ((0) && bad > good)
- fprintf(stderr, "Suspicious timings (%u > %u)\n", bad, good);
if (fname != argv[1])
unlink(fname);
io_uring_queue_exit(&ring);
