Re: [PATCH v2 19/19] afs: Maintain netfs_i_context::remote_i_size

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2022-03-08 at 23:30 +0000, David Howells wrote:
> Make afs use netfslib's tracking for the server's idea of what the current
> inode size is independently of inode->i_size.  We really want to use this
> value when calculating the new vnode size when initiating a StoreData RPC
> op rather than the size stat() presents to the user (ie. inode->i_size) as
> the latter is affected by as-yet uncommitted writes.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: linux-cachefs@redhat.com
> cc: linux-afs@lists.infradead.org
> 
> Link: https://lore.kernel.org/r/164623014626.3564931.8375344024648265358.stgit@warthog.procyon.org.uk/ # v1
> ---
> 
>  fs/afs/inode.c |    1 +
>  fs/afs/write.c |    7 +++----
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/afs/inode.c b/fs/afs/inode.c
> index 5b5e40197655..2fe402483ad5 100644
> --- a/fs/afs/inode.c
> +++ b/fs/afs/inode.c
> @@ -246,6 +246,7 @@ static void afs_apply_status(struct afs_operation *op,
>  		 * idea of what the size should be that's not the same as
>  		 * what's on the server.
>  		 */
> +		vnode->netfs_ctx.remote_i_size = status->size;
>  		if (change_size) {
>  			afs_set_i_size(vnode, status->size);
>  			inode->i_ctime = t;
> diff --git a/fs/afs/write.c b/fs/afs/write.c
> index e4b47f67a408..85c9056ba9fb 100644
> --- a/fs/afs/write.c
> +++ b/fs/afs/write.c
> @@ -353,9 +353,10 @@ static const struct afs_operation_ops afs_store_data_operation = {
>  static int afs_store_data(struct afs_vnode *vnode, struct iov_iter *iter, loff_t pos,
>  			  bool laundering)
>  {
> +	struct netfs_i_context *ictx = &vnode->netfs_ctx;
>  	struct afs_operation *op;
>  	struct afs_wb_key *wbk = NULL;
> -	loff_t size = iov_iter_count(iter), i_size;
> +	loff_t size = iov_iter_count(iter);
>  	int ret = -ENOKEY;
>  
>  	_enter("%s{%llx:%llu.%u},%llx,%llx",
> @@ -377,15 +378,13 @@ static int afs_store_data(struct afs_vnode *vnode, struct iov_iter *iter, loff_t
>  		return -ENOMEM;
>  	}
>  
> -	i_size = i_size_read(&vnode->vfs_inode);
> -
>  	afs_op_set_vnode(op, 0, vnode);
>  	op->file[0].dv_delta = 1;
>  	op->file[0].modification = true;
>  	op->store.write_iter = iter;
>  	op->store.pos = pos;
>  	op->store.size = size;
> -	op->store.i_size = max(pos + size, i_size);
> +	op->store.i_size = max(pos + size, ictx->remote_i_size);

Ahh ok, so if i_size is larger than is represented by this write, you'll
have a zeroed out region until writeback catches up. Makes sense.

>  	op->store.laundering = laundering;
>  	op->mtime = vnode->vfs_inode.i_mtime;
>  	op->flags |= AFS_OPERATION_UNINTR;
> 
> 

Reviewed-by: Jeff Layton <jlayton@kernel.org>