From patchwork Thu Jan 30 17:09:45 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brian Foster X-Patchwork-Id: 13954738 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 0D8EE1EF09C for ; Thu, 30 Jan 2025 17:07:45 +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=1738256867; cv=none; b=syaNtRskQNVUF/bMgIGpQSWhiiBXbd/XKZtJM2qnV0QkponYsv1tQGBe78Ga3Pm7doxu1y3gg7R4ttjEAvuefsx9rgJ4jOGaHgG0A97ASr4xC4IEW2OR//dnJZIixDDbcN4Og+nKMvjSZw+YCZsO0rKLABkj7WzI54goYaSk+0M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738256867; c=relaxed/simple; bh=2EOnyOMwZ274Xu9BeWjH6QaNCnCk54bo7FxMTpbrYyc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=ZdkdAGuhXoJzDfa6x7kmttPF5yEHVOeeudnoFQJ5gcLHEDxpXhxORzpiUBAl55814J0yvo2hjttHpU6vBzLBn7keiDO+7kokOT0hRcGIMfbcIwbSo/gk3klPgvHrP/bruDmoX/o2VFZxNH9W/Uyq+u8AYJlsEeB9/q+FfZqK6LE= 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=SMcVI+8v; 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="SMcVI+8v" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1738256865; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GMObJwhpN7907bRscANbVFOkK7nf5mppGoAUAR3Vh4s=; b=SMcVI+8vs4Ta6YAJdDDi5oaUZGRJJhXzp0FJOunFM5XRMV1CtmFcbcvkydZknqeTWgNAiz K8Dw7ggsDiXXPBNx9R/VFmxoALXm5kD2bD+1m3UVTa5P5dODqLv6o8V9NHRN2xcAc5VZNu vK6Sy2yMKeSDEfVMT+n6cxy2ItBnXaE= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-617-Mt32DkfjOIqWJdklwAus-A-1; Thu, 30 Jan 2025 12:07:41 -0500 X-MC-Unique: Mt32DkfjOIqWJdklwAus-A-1 X-Mimecast-MFC-AGG-ID: Mt32DkfjOIqWJdklwAus-A Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B3728180036E; Thu, 30 Jan 2025 17:07:40 +0000 (UTC) Received: from bfoster.redhat.com (unknown [10.22.80.113]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id E7C2230001BE; Thu, 30 Jan 2025 17:07:39 +0000 (UTC) From: Brian Foster To: linux-fsdevel@vger.kernel.org Cc: linux-xfs@vger.kernel.org, Christoph Hellwig Subject: [PATCH v3 4/7] iomap: support incremental iomap_iter advances Date: Thu, 30 Jan 2025 12:09:45 -0500 Message-ID: <20250130170949.916098-5-bfoster@redhat.com> In-Reply-To: <20250130170949.916098-1-bfoster@redhat.com> References: <20250130170949.916098-1-bfoster@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 The current iomap_iter iteration model reads the mapping from the filesystem, processes the subrange of the operation associated with the current mapping, and returns the number of bytes processed back to the iteration code. The latter advances the position and remaining length of the iter in preparation for the next iteration. At the _iter() handler level, this tends to produce a processing loop where the local code pulls the current position and remaining length out of the iter, iterates it locally based on file offset, and then breaks out when the associated range has been fully processed. This works well enough for current handlers, but upcoming enhancements require a bit more flexibility in certain situations. Enhancements for zero range will lead to a situation where the processing loop is no longer a pure ascending offset walk, but rather dictated by pagecache state and folio lookup. Since folio lookup and write preparation occur at different levels, it is more difficult to manage position and length outside of the iter. To provide more flexibility to certain iomap operations, introduce support for incremental iomap_iter advances from within the operation itself. This allows more granular advances for operations that might not use the typical file offset based walk. Note that the semantics for operations that use incremental advances is slightly different than traditional operations. Operations that advance the iter directly are expected to return success or failure (i.e. 0 or negative error code) in iter.processed rather than the number of bytes processed. Signed-off-by: Brian Foster Reviewed-by: Christoph Hellwig --- fs/iomap/iter.c | 32 +++++++++++++++++++++++++------- include/linux/iomap.h | 3 +++ 2 files changed, 28 insertions(+), 7 deletions(-) diff --git a/fs/iomap/iter.c b/fs/iomap/iter.c index 0a13d50e9ffd..bb56996de09d 100644 --- a/fs/iomap/iter.c +++ b/fs/iomap/iter.c @@ -35,6 +35,8 @@ static inline void iomap_iter_done(struct iomap_iter *iter) WARN_ON_ONCE(iter->iomap.offset + iter->iomap.length <= iter->pos); WARN_ON_ONCE(iter->iomap.flags & IOMAP_F_STALE); + iter->iter_start_pos = iter->pos; + trace_iomap_iter_dstmap(iter->inode, &iter->iomap); if (iter->srcmap.type != IOMAP_HOLE) trace_iomap_iter_srcmap(iter->inode, &iter->srcmap); @@ -58,6 +60,8 @@ static inline void iomap_iter_done(struct iomap_iter *iter) int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops) { bool stale = iter->iomap.flags & IOMAP_F_STALE; + ssize_t advanced = iter->processed > 0 ? iter->processed : 0; + u64 olen = iter->len; s64 processed; int ret; @@ -66,11 +70,22 @@ int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops) if (!iter->iomap.length) goto begin; + /* + * If iter.processed is zero, the op may still have advanced the iter + * itself. Calculate the advanced and original length bytes based on how + * far pos has advanced for ->iomap_end(). + */ + if (!advanced) { + advanced = iter->pos - iter->iter_start_pos; + olen += advanced; + } + if (ops->iomap_end) { - ret = ops->iomap_end(iter->inode, iter->pos, iomap_length(iter), - iter->processed > 0 ? iter->processed : 0, - iter->flags, &iter->iomap); - if (ret < 0 && !iter->processed) + ret = ops->iomap_end(iter->inode, iter->iter_start_pos, + iomap_length_trim(iter, iter->iter_start_pos, + olen), + advanced, iter->flags, &iter->iomap); + if (ret < 0 && !advanced) return ret; } @@ -81,8 +96,11 @@ int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops) } /* - * Advance the iter and clear state from the previous iteration. The - * remaining length of the previous iteration should be zero by this + * Advance the iter and clear state from the previous iteration. This + * passes iter->processed because that reflects the bytes processed but + * not yet advanced by the iter handler. + * + * The remaining length of the previous iteration should be zero by this * point, so use iter->len to determine whether to continue onto the * next mapping. Explicitly terminate in the case where the current iter * has not advanced at all (i.e. no work was done for some reason) @@ -91,7 +109,7 @@ int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops) ret = iomap_iter_advance(iter, &processed); if (!ret && iter->len > 0) ret = 1; - if (ret > 0 && !iter->processed && !stale) + if (ret > 0 && !advanced && !stale) ret = 0; iomap_iter_reset_iomap(iter); if (ret <= 0) diff --git a/include/linux/iomap.h b/include/linux/iomap.h index f304c602e5fe..0135a7f8dd83 100644 --- a/include/linux/iomap.h +++ b/include/linux/iomap.h @@ -211,6 +211,8 @@ struct iomap_ops { * calls to iomap_iter(). Treat as read-only in the body. * @len: The remaining length of the file segment we're operating on. * It is updated at the same time as @pos. + * @iter_start_pos: The original start pos for the current iomap. Used for + * incremental iter advance. * @processed: The number of bytes processed by the body in the most recent * iteration, or a negative errno. 0 causes the iteration to stop. * @flags: Zero or more of the iomap_begin flags above. @@ -221,6 +223,7 @@ struct iomap_iter { struct inode *inode; loff_t pos; u64 len; + loff_t iter_start_pos; s64 processed; unsigned flags; struct iomap iomap;