Re:Re: [PATCH] mm/filemap.c: clear page error before actual read

[田 <xianting_tian@xxxxxxx>]

thanks for your reply:)

totally agree, it is more accurate as below, I will send the patch again, thanks.

>+	ClearPageError(page);
>        goto filler;

At 2020-03-04 00:43:17, "Matthew Wilcox" <willy@xxxxxxxxxxxxx> wrote:
>On Tue, Mar 03, 2020 at 10:09:50AM -0500, Xianting Tian wrote:
>> This patch is to add the calling of ClearPageError just before the
>> actual read of read path of cramfs mount.
>
>Thank you for your patch and your analysis.  I concur; an error set
>on a page will not be cleared by doing a subsequent read.  This is
>probably an oversight; in generic_file_buffered_read(), we do:
>
>                ClearPageError(page);
>                /* Start the actual read. The read will unlock the page. */
>                error = mapping->a_ops->readpage(filp, page);
>
>and also in filemap_fault:
>
>        ClearPageError(page);
>        fpin = maybe_unlock_mmap_for_io(vmf, fpin);
>        error = mapping->a_ops->readpage(file, page);
>
>That said, a freshly allocated page will not have PageError set on
>it, so I would prefer to see this:
>
>        /* Someone else locked and filled the page in a very small window */
>        if (PageUptodate(page)) {
>                unlock_page(page);
>                goto out;
>        }
>+	ClearPageError(page);
>        goto filler;