[Cluster-devel] [GFS2] flush the log if a transaction can't allocate space

[Steven Whitehouse]

Hi,

Now applied to the -nmw git tree. Thanks,

Steve.

On Fri, 2007-03-23 at 14:51 -0600, Benjamin Marzinski wrote:
> This is a fix for bz #208514. When GFS2 frees up space, the freed blocks
> aren't available for reuse until the resource group is successfully written
> to the ondisk journal. So in rare cases, GFS2 operations will fail, saying
> that the filesystem is out of space, when in reality, you are just waiting for
> a log flush. For instance, on a 1Gig filesystem, if I continually write 10 Mb
> to a file, and then truncate it, after a hundred interations, the write will
> fail with -ENOSPC, even though the filesystem is just 1% full.
> 
> The attached patch calls a log flush in these cases.  I tested this patch
> fairly heavily to check if there were any locking issues that I missed, and
> it seems to work just fine. Also, this patch only does the log flush if
> get_local_rgrp makes a complete loop of resource groups without skipping
> any do to locking issues. The code would be slightly simpler if it just always
> did the log flush after the first failed pass, and you could only ever have
> to go through the loop twice, instead of up to three times. However, I guessed
> that failing to find a rg simply do to locking issues would be common enough
> to skip the log flush in that case, but I'm not certain that this is the right
> way to go. Either way, I don't suppose this code will be hit all that often.
> 
> Signed-off-by: Benjamin E. Marzinski <bmarzins at redhat.com>
> 
> plain text document attachment (flush_if_full.patch)
> diff -urpN gfs2-2.6-nmw-new-clean/fs/gfs2/rgrp.c gfs2-2.6-nmw-patched/fs/gfs2/rgrp.c
> --- gfs2-2.6-nmw-new-clean/fs/gfs2/rgrp.c	2007-03-19 17:23:35.000000000 -0500
> +++ gfs2-2.6-nmw-patched/fs/gfs2/rgrp.c	2007-03-22 12:43:39.000000000 -0500
> @@ -27,6 +27,7 @@
>  #include "trans.h"
>  #include "ops_file.h"
>  #include "util.h"
> +#include "log.h"
>  
>  #define BFITNOENT ((u32)~0)
>  
> @@ -941,9 +942,13 @@ static int get_local_rgrp(struct gfs2_in
>  			rgd = gfs2_rgrpd_get_first(sdp);
>  
>  		if (rgd == begin) {
> -			if (++loops >= 2 || !skipped)
> +			if (++loops >= 3)
>  				return -ENOSPC;
> +			if (!skipped)
> +				loops++;
>  			flags = 0;
> +			if (loops == 2)
> +				gfs2_log_flush(sdp, NULL);
>  		}
>  	}
>