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Re: [Cluster-devel] [PATCH] GFS2: make sure fallocate bytes is a multiple of blksize



Hi,

Now in the -nmw GFS2 git tree. Thanks,

Steve.

On Tue, 2011-04-26 at 01:13 -0500, Benjamin Marzinski wrote:
> The GFS2 fallocate code chooses a target size to for allocating chunks of
> space.  Whenever it can't find any resource groups with enough space free, it
> halves its target. Since this target is in bytes, eventually it will no longer
> be a multiple of blksize.  As long as there is more space available in the
> resource group than the target, this isn't a problem, since gfs2 will use the
> actual space available, which is always a multiple of blksize.  However,
> when gfs couldn't fallocate a bigger chunk than the target, it was using the
> non-blksize aligned number. This caused a BUG in later code that required
> blksize aligned offsets.  GFS2 now ensures that bytes is always a multiple of
> blksize
> 
> Signed-off-by: Benjamin Marzinski <bmarzins redhat com>
> ---
>  fs/gfs2/file.c |   10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> Index: gfs2-2.6-nmw/fs/gfs2/file.c
> ===================================================================
> --- gfs2-2.6-nmw.orig/fs/gfs2/file.c
> +++ gfs2-2.6-nmw/fs/gfs2/file.c
> @@ -816,6 +816,7 @@ static long gfs2_fallocate(struct file *
>  	loff_t bytes, max_bytes;
>  	struct gfs2_alloc *al;
>  	int error;
> +	loff_t bsize_mask = ~((loff_t)sdp->sd_sb.sb_bsize - 1);
>  	loff_t next = (offset + len - 1) >> sdp->sd_sb.sb_bsize_shift;
>  	next = (next + 1) << sdp->sd_sb.sb_bsize_shift;
>  
> @@ -823,13 +824,15 @@ static long gfs2_fallocate(struct file *
>  	if (mode & ~FALLOC_FL_KEEP_SIZE)
>  		return -EOPNOTSUPP;
>  
> -	offset = (offset >> sdp->sd_sb.sb_bsize_shift) <<
> -		 sdp->sd_sb.sb_bsize_shift;
> +	offset &= bsize_mask;
>  
>  	len = next - offset;
>  	bytes = sdp->sd_max_rg_data * sdp->sd_sb.sb_bsize / 2;
>  	if (!bytes)
>  		bytes = UINT_MAX;
> +	bytes &= bsize_mask;
> +	if (bytes == 0)
> +		bytes = sdp->sd_sb.sb_bsize;
>  
>  	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &ip->i_gh);
>  	error = gfs2_glock_nq(&ip->i_gh);
> @@ -860,6 +863,9 @@ retry:
>  		if (error) {
>  			if (error == -ENOSPC && bytes > sdp->sd_sb.sb_bsize) {
>  				bytes >>= 1;
> +				bytes &= bsize_mask;
> +				if (bytes == 0)
> +					bytes = sdp->sd_sb.sb_bsize;
>  				goto retry;
>  			}
>  			goto out_qunlock;
> 



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