Re: [PATCH] pipe: increase minimum default pipe size to 2 pages

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Aug 04, 2021 at 08:04:35PM -0400, Alex Xu (Hello71) wrote:
> Before this patch, the following program prints 4096 and hangs.
> Afterwards, it prints 8192 and exits successfully. Note that you may
> need to increase your RLIMIT_NOFILE before running the program.
> 
> int main() {
>     int pipefd[2];
>     for (int i = 0; i < 1025; i++)
>         if (pipe(pipefd) == -1)
>             return 1;
>     size_t bufsz = fcntl(pipefd[1], F_GETPIPE_SZ);
>     printf("%zd\n", bufsz);
>     char *buf = calloc(bufsz, 1);
>     write(pipefd[1], buf, bufsz);
>     read(pipefd[0], buf, bufsz-1);
>     write(pipefd[1], buf, 1);
> }
> 
> Signed-off-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca>
> ---

Is this due to the changes that happened in 5.5?  If so, a cc: stable
and a fixes tag would be nice to have :)

> See discussion at https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.

This can go up in the changelog text too.

thanks,

greg k-h