Re: Is writeback_iter() missing some error handling? -- was Re: [PATCH] netfs: fix ENOMEM handling in netfs_writepages() to drain all dirty folios

[Matthew Wilcox <willy@infradead.org>]

On Wed, Jul 22, 2026 at 03:04:03PM +0100, David Howells wrote:
> This seems like the wrong thing to do - or, at least, a bug in the
> writeback_iter() API.  Getting something like ENOMEM would seem to indicate
> that all subsequent writeback_iter() calls in this loop are pointless as it
> looks like the sequence will just go { lock, undirty, dirty, unlock } for each
> folio.

I'd find it hard to call a bug, when it's intended behaviour:

                 * For integrity writeback we have to keep going until we have
                 * written all the folios we tagged for writeback above, even if
                 * we run past wbc->nr_to_write or encounter errors.
                 * We stash away the first error we encounter in wbc->saved_err
                 * so that it can be retrieved when we're done.  This is because
                 * the file system may still have state to clear for each folio.
                 *
                 * For background writeback we exit as soon as we run past
                 * wbc->nr_to_write or encounter the first error.

Why are you getting ENOMEM for a sync() writeback anyway?  Is this some
stupid error injection?