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Message-ID: <2330754.1673943968@warthog.procyon.org.uk>
Date: Tue, 17 Jan 2023 08:26:08 +0000
From: David Howells <dhowells@...hat.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: dhowells@...hat.com, Al Viro <viro@...iv.linux.org.uk>,
Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
Christoph Hellwig <hch@....de>,
Matthew Wilcox <willy@...radead.org>,
Logan Gunthorpe <logang@...tatee.com>,
linux-block@...r.kernel.org, Jeff Layton <jlayton@...nel.org>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 11/34] iov_iter, block: Make bio structs pin pages rather than ref'ing if appropriate
Christoph Hellwig <hch@...radead.org> wrote:
> > + bio_clear_flag(bio, BIO_PAGE_REFFED);
>
> .. and this should not be needed. Instead:
>
> > + cleanup_mode = iov_iter_extract_mode(iter, gup_flags);
> > + if (cleanup_mode & FOLL_GET)
> > + bio_set_flag(bio, BIO_PAGE_REFFED);
> > + if (cleanup_mode & FOLL_PIN)
> > + bio_set_flag(bio, BIO_PAGE_PINNED);
>
> We could warn if a not match flag is set here if we really care.
Um... With these patches, BIO_PAGE_REFFED is set by default when the bio is
initialised otherwise every user of struct bio that currently adds pages
directly (assuming there are any) rather than going through
bio_iov_iter_get_pages() will have to set the flag, hence the need to clear
it.
Actually, I could do:
if (!(cleanup_mode & FOLL_GET))
bio_clear_flag(bio, BIO_PAGE_REFFED);
if (cleanup_mode & FOLL_PIN)
bio_set_flag(bio, BIO_PAGE_PINNED);
which should also work.
David
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