Messages in this thread | | | Date | Wed, 12 Jan 2022 13:19:32 +0000 | From | Matthew Wilcox <> | Subject | Re: [PATCH v3 RESEND] mm: shmem: implement POSIX_FADV_[WILL|DONT]NEED for shmem |
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On Wed, Jan 12, 2022 at 01:51:55PM +0530, Charan Teja Kalla wrote: > >>> + rcu_read_lock(); > >>> + xas_for_each(&xas, page, end) { > >>> + if (!xa_is_value(page)) > >>> + continue; > >>> + xas_pause(&xas); > >>> + rcu_read_unlock(); > >>> + > >>> + page = shmem_read_mapping_page(mapping, xas.xa_index); > >>> + if (!IS_ERR(page)) > >>> + put_page(page); > >>> + > >>> + rcu_read_lock(); > >>> + if (need_resched()) { > >>> + xas_pause(&xas); > >>> + cond_resched_rcu(); > >>> + } > >>> + } > >>> + rcu_read_unlock(); > > Even the xarray documentation says that: If most entries found during a > > walk require you to call xas_pause(), the xa_for_each() iterator may be > > more appropriate.
Yes. This should obviously be an xa_for_each() loop.
> > Since every value entry found in the xarray requires me to do the > > xas_pause(), I do agree that xa_for_each() is the appropriate call here. > > Will switch to this in the next spin. Waiting for further review > > comments on this patch. > > I also found the below documentation: > xa_for_each() will spin if it hits a retry entry; if you intend to see > retry entries, you should use the xas_for_each() iterator instead. > > Since retry entries are expected, I should be using the xas_for_each() > with the corrections you had pointed out. Isn't it?
No. You aren't handling retry entries at all; you clearly don't expect to see them. Just let the XArray code handle them itself.
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