On Mon, Jan 29, 2024 at 12:15 PM David Howells <dhowells@xxxxxxxxxx> wrote:
>
> Dave Wysochanski <dwysocha@xxxxxxxxxx> wrote:
>
> > - xas_lock(&xas);
> > + xas_lock_irqsave(&xas, flags);
> > xas_for_each(&xas, page, last) {
>
> You probably want to use RCU, not xas_lock(). The pages are locked and so
> cannot be evicted from the xarray.
>
I tried RCU originally and ran into a problem because NFS can schedule
(see comment on line 328 below)
326 xas_lock_irqsave(&xas, flags);
327 xas_for_each(&xas, page, last) {
328 /* nfs_read_add_folio() may schedule() due to pNFS
layout and other RPCs */
329 xas_pause(&xas);
330 xas_unlock_irqrestore(&xas, flags);
331 err = nfs_read_add_folio(&pgio, ctx, page_folio(page));
332 if (err < 0) {
333 netfs->error = err;
334 goto out;
335 }
336 xas_lock_irqsave(&xas, flags);
337 }
338 xas_unlock_irqrestore(&xas, flags);
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