Re: pread() over NFS (again) [1.5.5.4]

> Christian Holtje <docwhat@gmail.com> wrote:
>> I have read all the threads on git having trouble with pread() and I  
>> didn't see anything to help.
> ...
>>   Receiving objects: 100% (253/253), 5.27 MiB | 9136 KiB/s, done.
>>   fatal: cannot pread pack file: No such file or directory
>>   fatal: index-pack failed
>> 
>> The end of the strace looks like so:
>> pread(3, "", 205, 1373)                 = 0
>> write(2, "fatal: cannot pread pack file: N"..., 57) = 57
>
> Hmmph.  So pread for a length of 205 can return 0 on NFS?  Is this
> a transient error?  If so, perhaps a patch like this might help:
>
> diff --git a/index-pack.c b/index-pack.c
> index 5ac91ba..737f757 100644
> --- a/index-pack.c
> +++ b/index-pack.c
> @@ -309,14 +309,19 @@ static void *get_data_from_pack(struct object_entry *obj)
>  	unsigned char *src, *data;
>  	z_stream stream;
>  	int st;
> +	int attempts = 0;
>  
>  	src = xmalloc(len);
>  	data = src;
>  	do {
>  		ssize_t n = pread(pack_fd, data + rdy, len - rdy, from + rdy);
> -		if (n <= 0)
> +		if (n <= 0) {
> +			if (n == 0 && ++attempts < 10)
> +				continue;
>  			die("cannot pread pack file: %s", strerror(errno));
> +		}
>  		rdy += n;
> +		attempts = 0;
>  	} while (rdy < len);
>  	data = xmalloc(obj->size);
>  	memset(&stream, 0, sizeof(stream));
>
>
> The file shouldn't be short unless someone truncated it, or there
> is a bug in index-pack.  Neither is very likely, but I don't think
> we would want to retry pread'ing the same block forever.