Re: [PATCH] cachefiles: Fix incorrect length to fallocate()

[Jeff Layton]

On Thu, 2022-03-03 at 11:55 +0000, David Howells wrote:
> When cachefiles_shorten_object() calls fallocate() to shape the cache file
> to match the DIO size, it passes the total file size it wants to achieve,
> not the amount of zeros that should be inserted.  Since this is meant to
> preallocate that amount of storage for the file, it can cause the cache to
> fill up the disk and hit ENOSPC.
> 
> Fix this by passing the length actually required to go from the current EOF
> to the desired EOF.
> 
> Fixes: 7623ed6772de ("cachefiles: Implement cookie resize for truncate")
> Reported-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> cc: linux-cachefs@xxxxxxxxxx
> ---
> 
>  fs/cachefiles/interface.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
> index 51c968cd00a6..ae93cee9d25d 100644
> --- a/fs/cachefiles/interface.c
> +++ b/fs/cachefiles/interface.c
> @@ -254,7 +254,7 @@ static bool cachefiles_shorten_object(struct cachefiles_object *object,
>  		ret = cachefiles_inject_write_error();
>  		if (ret == 0)
>  			ret = vfs_fallocate(file, FALLOC_FL_ZERO_RANGE,
> -					    new_size, dio_size);
> +					    new_size, dio_size - new_size);
>  		if (ret < 0) {
>  			trace_cachefiles_io_error(object, file_inode(file), ret,
>  						  cachefiles_trace_fallocate_error);
> 
> 

Looks good!

I could often force the cache to fill up with the right fsstress run on
ceph, but with this in place I'm on the 5th run of xfstest generic/013
and it hasn't happened yet. You can add these if you like:

Tested-by: Jeff Layton <jlayton@xxxxxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>