Re: posix_fallocate() fails on some machines

[John Mudd <johnbmudd@gmail.com>]

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Thanks. It seems my mistake was to build on a VM with ext4 file system. My
intention was for the build VM to be the lowest common denominator of my
production PCs. That's why I use 32-bit. I'll change to ext3 on the build
VM.

On Thu, Apr 26, 2018 at 4:08 PM, Rich Felker <dalias@libc.org> wrote:

> On Thu, Apr 26, 2018 at 03:54:19PM -0400, John Mudd wrote:
> > I built a 32-bit dynamically linked Postgres using musl but I can't run
> on
> > some machines because posix_fallocate() returns 95, "not supported".
> >
> > Here's a sample program that reproduces the issue even when compiled
> > statically. Any suggestions?
> >
> > # Build a 32-bit static executable. Works.
> > $ cat test_posix_fallocate.c
> > #include <stdio.h>
> > #include <fcntl.h>
> > int main() {
> >     int fd = open("foo", O_RDWR|O_CREAT, 0666);
> >     if (fd < 0) return 1;
> >     printf("posix_fallocate() returned %d\n", posix_fallocate(fd, 0,
> > 400000));
> > }
> > $
> > $ uname -mrs
> > Linux 4.4.0-116-generic i686
> > $ musl-gcc -static -o test_posix_fallocate test_posix_fallocate.c
> > $ test_posix_fallocate
> > posix_fallocate() returned 0
> > $
> >
> > # Copy it to an older OS. Fails.
> > $ uname -mrs
> > Linux 2.6.32-358.14.1.el6.x86_64 x86_64
> > $ test_posix_fallocate
> > posix_fallocate() returned 95
> > $
>
> This is a bug in postgresql. It must accept that some underlying
> filesystems do not support posix_fallocate. The reason it doesn't is
> that glibc implements a buggy and dangerous fallback when it's not
> supported, resolved WONTFIX:
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=6865
>
> Simply patch postgresql not to consider this a fatal error, or use a
> filesystem where posix_fallocate is supported (e.g. ext3/4).
>
> Rich
>

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