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ul_copy_file: handle EAGAIN and EINTR 

I did this by implementing a function called sendfile_all() similar to
read_all()/write_all().

The manpage for sendfile doesn't mention EINTR, but I decided to check
it anyway, just in case.

Suggested-by: Karel Zak <kzak@redhat.com>
Reviewed-by: Sami Kerola <kerolasa@iki.fi>
Signed-off-by: Egor Chelak <egor.chelak@gmail.com>
This commit is contained in:
Egor Chelak 2020-11-06 20:33:46 +02:00
parent f19a16550a
commit 212bde6cf7
2 changed files with 36 additions and 13 deletions
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32
include/all-io.h
View File

@ -12,6 +12,10 @@
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#ifdef HAVE_SENDFILE
#include <sys/sendfile.h>
#endif
#include "c.h"
@ -78,4 +82,32 @@ static inline ssize_t read_all(int fd, char *buf, size_t count)
return c;
}
static inline ssize_t sendfile_all(int out, int in, off_t *off, size_t count)
{
#ifdef HAVE_SENDFILE
ssize_t ret;
ssize_t c = 0;
int tries = 0;
while (count) {
ret = sendfile(out, in, off, count);
if (ret < 0) {
if ((errno == EAGAIN || errno == EINTR) && (tries++ < 5)) {
xusleep(250000);
continue;
}
return c ? c : -1;
}
if (ret == 0)
return c;
tries = 0;
count -= ret;
c += ret;
}
return c;
#else
errno = ENOSYS;
return -1;
#endif
}
#endif /* UTIL_LINUX_ALL_IO_H */

17
lib/fileutils.c
View File

@ -11,9 +11,6 @@
#include <unistd.h>
#include <sys/time.h>
#include <sys/resource.h>
#ifdef HAVE_SENDFILE
#include <sys/sendfile.h>
#endif
#include <string.h>
#include "c.h"
@ -275,21 +272,15 @@ int ul_copy_file(int from, int to)
#ifdef HAVE_SENDFILE
struct stat st;
ssize_t nw;
off_t left;
if (fstat(from, &st) == -1)
return -1;
if (!S_ISREG(st.st_mode))
return copy_file_simple(from, to);
for (left = st.st_size; left != 0; left -= nw) {
if ((nw = sendfile(to, from, NULL, left)) < 0)
return copy_file_simple(from, to);
if (!nw)
return 0;
}
/* For extra robustness, treat st_size as advisory and ensure that we
* actually get EOF. */
while ((nw = sendfile(to, from, NULL, 1024*1024)) != 0)
if (sendfile_all(to, from, NULL, st.st_size) < 0)
return copy_file_simple(from, to);
/* ensure we either get an EOF or an error */
while ((nw = sendfile_all(to, from, NULL, 16*1024*1024)) != 0)
if (nw < 0)
return copy_file_simple(from, to);
return 0;