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cache: tolerate short writes in print_slot

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sendfile() can return after a short read/write, so we may need to call
it more than once. As suggested in the manual page, we fall back to
read/write if sendfile fails with EINVAL or ENOSYS.

On the read/write path, use write_in_full which deals with short writes.

Signed-off-by: Hristo Venev <hristo@venev.name>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Hristo Venev 2022-05-07 20:07:00 +03:00 committed by Jason A. Donenfeld
parent 4c520cefc9
commit 852cb3b0e2
1 changed files with 25 additions and 20 deletions
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39
cache.c
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@ -85,40 +85,45 @@ static int close_slot(struct cache_slot *slot)
/* Print the content of the active cache slot (but skip the key). */
static int print_slot(struct cache_slot *slot)
{
off_t off;
#ifdef HAVE_LINUX_SENDFILE
off_t start_off;
int ret;
off_t size;
#endif
start_off = slot->keylen + 1;
off = slot->keylen + 1;
#ifdef HAVE_LINUX_SENDFILE
size = slot->cache_st.st_size;
do {
ret = sendfile(STDOUT_FILENO, slot->cache_fd, &start_off,
slot->cache_st.st_size - start_off);
ssize_t ret;
ret = sendfile(STDOUT_FILENO, slot->cache_fd, &off, size - off);
if (ret < 0) {
if (errno == EAGAIN || errno == EINTR)
continue;
/* Fall back to read/write on EINVAL or ENOSYS */
if (errno == EINVAL || errno == ENOSYS)
break;
return errno;
}
if (off == size)
return 0;
} while (1);
#else
ssize_t i, j;
#endif
i = lseek(slot->cache_fd, slot->keylen + 1, SEEK_SET);
if (i != slot->keylen + 1)
if (lseek(slot->cache_fd, off, SEEK_SET) != off)
return errno;
do {
i = j = xread(slot->cache_fd, slot->buf, sizeof(slot->buf));
if (i > 0)
j = xwrite(STDOUT_FILENO, slot->buf, i);
} while (i > 0 && j == i);
if (i < 0 || j != i)
ssize_t ret;
ret = xread(slot->cache_fd, slot->buf, sizeof(slot->buf));
if (ret < 0)
return errno;
else
if (ret == 0)
return 0;
#endif
if (write_in_full(STDOUT_FILENO, slot->buf, ret) < 0)
return errno;
} while (1);
}
/* Check if the slot has expired */