On Tue, May 22, 2018 at 10:41:11AM -0700, Omar Sandoval wrote:
> On Tue, May 22, 2018 at 10:37:14AM -0700, Omar Sandoval wrote:
> > On Tue, May 22, 2018 at 07:17:48PM +0200, David Sterba wrote:
> > > On Tue, May 22, 2018 at 09:47:58AM -0700, Omar Sandoval wrote:
> > > > From: Omar Sandoval <osandov@xxxxxx>
> > > >
> > > > Jun Wu at Facebook reported that an internal service was seeing a return
> > > > value of 1 from ftruncate() on Btrfs in some cases.
> > >
> > > Do you have a reproducer? To estimate how likely is to hit the problem
> > > in practice.
Okay last one, I promise, we just need the extent items to be on disk:
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(void) {
char buf[256] = { 0 };
int ret;
int fd;
fd = open("test", O_CREAT | O_WRONLY | O_TRUNC, 0666);
if (fd == -1) {
perror("open");
return EXIT_FAILURE;
}
if (write(fd, buf, sizeof(buf)) != sizeof(buf)) {
perror("write");
close(fd);
return EXIT_FAILURE;
}
if (fsync(fd) == -1) {
perror("fsync");
close(fd);
return EXIT_FAILURE;
}
ret = ftruncate(fd, 128);
if (ret) {
printf("ftruncate() returned %d\n", ret);
close(fd);
return EXIT_FAILURE;
}
close(fd);
return EXIT_SUCCESS;
}
Basically, any time we truncate a compressed, inline file, as long as
its extents are already on disk, we get the erroneous return value.
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