Re: [PATCH 6/6] NFS: return -EAGAIN when skipped commit in nfs_commit_unstable_pages()

Trond Myklebust
2011-04-19T03:29:11Z

On Tue, 2011-04-19 at 11:00 +0800, Wu Fengguang wrote:
> plain text document attachment (nfs-fix-write_inode-retval.patch)
> It's probably not sane to return success while redirtying the inode at
> the same time in ->write_inode().
>
> CC: Trond Myklebust <Trond.Myklebust@netapp.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> ---
> fs/nfs/write.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- linux-next.orig/fs/nfs/write.c 2011-04-19 10:18:16.000000000 +0800
> +++ linux-next/fs/nfs/write.c 2011-04-19 10:18:32.000000000 +0800
> @@ -1519,7 +1519,7 @@ static int nfs_commit_unstable_pages(str
> {
> struct nfs_inode *nfsi = NFS_I(inode);
> int flags = FLUSH_SYNC;
> - int ret = 0;
> + int ret = -EAGAIN;
>
> if (wbc->sync_mode == WB_SYNC_NONE) {
> /* Don't commit yet if this is a non-blocking flush and there
>
>

Hi Fengguang,

I don't understand the purpose of this patch...

Currently, the value of 'ret' only affects the case where the commit
exits early due to this being a non-blocking flush where we have not yet
written back enough pages to make it worth our while to send a commit.

In essence, this really only matters for the cases where someone calls
'write_inode_now' (not used by anybody calling into the NFS client) and
'sync_inode', which is only called by nfs_wb_all (with sync_mode =
WB_SYNC_ALL).

So can you please elaborate on the possible use cases for this change?

Cheers
Trond
--
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com