From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 649D320696E for ; Tue, 12 Nov 2024 16:36:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731429379; cv=none; b=h1YGafsceG8ei9aSUtf1L4PPdQugrYnmwUCaqSg23YHVBNXP2oZYKIQv1QivDK7rwuBFaNn9rpG9as7/2INiFBB2JS1t3hRP22yC4UFvJk02Ehg9G+Z3WNLJXo/x1quvJVzNgcJ6zNpGRxiMAVRklrHHUATCIEmELpe1Sr6hb0U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731429379; c=relaxed/simple; bh=O8YWXr0yLvNtoKRSJ3Vixa5YPoUh9gJ0YaA225ooMQk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=AxtxhqTv6Qf8XRqusYZSQw6Tvg6qszYksRME5JilewxsYZqBhN3LZy36CxQU1aoRQ+ujCrHJBk6jRG+hiLN2xP81RnB2tXpVkkG4x10356406uTDrdSNGE+fc6yOfgd+cGskxXw64YwxoxWq6LsnMuAc/QonBG5UGu1K1LBUe70= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=EoTSedlM; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="EoTSedlM" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1731429376; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Vshv/5C+8AN3xRIpFFRaIA6JN4+z8qS1tz/4w33plCw=; b=EoTSedlM91WhLCTIsrp5AiZAgxTWtisEqsxXAe1Y7aDCPFXynMKQ0cy9F6S9vgJ7e2cAOY UNYcwxm4nuQ1mjarCBayLJh6morsJ6MZQ6+v4I6E0FpZ4nXjkEtKxQj3CMScEnTz6a3G+v UyU6iXsWJjbKjhocqmdEkwK7s2jesGs= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-169-2e90iJDzPXGIadG2_ei9PQ-1; Tue, 12 Nov 2024 11:36:14 -0500 X-MC-Unique: 2e90iJDzPXGIadG2_ei9PQ-1 X-Mimecast-MFC-AGG-ID: 2e90iJDzPXGIadG2_ei9PQ Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E7CEF19560B8; Tue, 12 Nov 2024 16:36:12 +0000 (UTC) Received: from bfoster (unknown [10.22.80.120]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CFDC819560A3; Tue, 12 Nov 2024 16:36:10 +0000 (UTC) Date: Tue, 12 Nov 2024 11:37:43 -0500 From: Brian Foster To: Jens Axboe Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, hannes@cmpxchg.org, clm@meta.com, linux-kernel@vger.kernel.org, willy@infradead.org, kirill@shutemov.name, linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org Subject: Re: [PATCH 13/16] iomap: make buffered writes work with RWF_UNCACHED Message-ID: References: <20241111234842.2024180-1-axboe@kernel.dk> <20241111234842.2024180-14-axboe@kernel.dk> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241111234842.2024180-14-axboe@kernel.dk> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 On Mon, Nov 11, 2024 at 04:37:40PM -0700, Jens Axboe wrote: > Add iomap buffered write support for RWF_UNCACHED. If RWF_UNCACHED is > set for a write, mark the folios being written with drop_writeback. Then s/drop_writeback/uncached/ ? BTW, this might be getting into wonky "don't care that much" territory, but something else to be aware of is that certain writes can potentially change pagecache state as a side effect outside of the actual buffered write itself. For example, xfs calls iomap_zero_range() on write extension (i.e. pos > isize), which uses buffered writes and thus could populate a pagecache folio without setting it uncached, even if done on behalf of an uncached write. I've only made a first pass and could be missing some details, but IIUC I _think_ this means something like writing out a stream of small, sparse and file extending uncached writes could actually end up behaving more like sync I/O. Again, not saying that's something we really care about, just raising it in case it's worth considering or documenting.. Brian > writeback completion will drop the pages. The write_iter handler simply > kicks off writeback for the pages, and writeback completion will take > care of the rest. > > This still needs the user of the iomap buffered write helpers to call > iocb_uncached_write() upon successful issue of the writes. > > Signed-off-by: Jens Axboe > --- > fs/iomap/buffered-io.c | 15 +++++++++++++-- > include/linux/iomap.h | 4 +++- > 2 files changed, 16 insertions(+), 3 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index ef0b68bccbb6..2f2a5db04a68 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -603,6 +603,8 @@ struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len) > > if (iter->flags & IOMAP_NOWAIT) > fgp |= FGP_NOWAIT; > + if (iter->flags & IOMAP_UNCACHED) > + fgp |= FGP_UNCACHED; > fgp |= fgf_set_order(len); > > return __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT, > @@ -1023,8 +1025,9 @@ ssize_t > iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i, > const struct iomap_ops *ops, void *private) > { > + struct address_space *mapping = iocb->ki_filp->f_mapping; > struct iomap_iter iter = { > - .inode = iocb->ki_filp->f_mapping->host, > + .inode = mapping->host, > .pos = iocb->ki_pos, > .len = iov_iter_count(i), > .flags = IOMAP_WRITE, > @@ -1034,9 +1037,14 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i, > > if (iocb->ki_flags & IOCB_NOWAIT) > iter.flags |= IOMAP_NOWAIT; > + if (iocb->ki_flags & IOCB_UNCACHED) > + iter.flags |= IOMAP_UNCACHED; > > - while ((ret = iomap_iter(&iter, ops)) > 0) > + while ((ret = iomap_iter(&iter, ops)) > 0) { > + if (iocb->ki_flags & IOCB_UNCACHED) > + iter.iomap.flags |= IOMAP_F_UNCACHED; > iter.processed = iomap_write_iter(&iter, i); > + } > > if (unlikely(iter.pos == iocb->ki_pos)) > return ret; > @@ -1770,6 +1778,9 @@ static int iomap_add_to_ioend(struct iomap_writepage_ctx *wpc, > size_t poff = offset_in_folio(folio, pos); > int error; > > + if (folio_test_uncached(folio)) > + wpc->iomap.flags |= IOMAP_F_UNCACHED; > + > if (!wpc->ioend || !iomap_can_add_to_ioend(wpc, pos)) { > new_ioend: > error = iomap_submit_ioend(wpc, 0); > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index f61407e3b121..2efc72df19a2 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h > @@ -64,6 +64,7 @@ struct vm_fault; > #define IOMAP_F_BUFFER_HEAD 0 > #endif /* CONFIG_BUFFER_HEAD */ > #define IOMAP_F_XATTR (1U << 5) > +#define IOMAP_F_UNCACHED (1U << 6) > > /* > * Flags set by the core iomap code during operations: > @@ -173,8 +174,9 @@ struct iomap_folio_ops { > #define IOMAP_NOWAIT (1 << 5) /* do not block */ > #define IOMAP_OVERWRITE_ONLY (1 << 6) /* only pure overwrites allowed */ > #define IOMAP_UNSHARE (1 << 7) /* unshare_file_range */ > +#define IOMAP_UNCACHED (1 << 8) /* uncached IO */ > #ifdef CONFIG_FS_DAX > -#define IOMAP_DAX (1 << 8) /* DAX mapping */ > +#define IOMAP_DAX (1 << 9) /* DAX mapping */ > #else > #define IOMAP_DAX 0 > #endif /* CONFIG_FS_DAX */ > -- > 2.45.2 > >