From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 54ABF9460; Tue, 15 Jul 2025 05:22:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752556980; cv=none; b=XChqxIyoEYXs2el9fhn0XHpUTDpx7h9Dw8sGoaWughV+DV9ao8JyMSTAsSNSqH0bZ1R4IVN2/wuRbvt0r17ITEhzbq8PVB9Cei7JOHFGTQWK3KmvglnNj2XQoiBX9Bt5yjfLiiRIueMTu8G7Tdh7SQpqtfwF95ZMpgbR+LYTbRc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752556980; c=relaxed/simple; bh=LTZ1AAoCssxZeCqtSQnDVFl3TA+mLje+mRQuY/tkaFk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HYtTNAZ4xF+sX5LydRh5wpSG8cs42WkEzYHqa8Er67/rNECpJygGqsjbCQzNDz3YK8bJ4bGuihp0mBzpNxqfAIyAQ/Hh3cR+up9fM35v6UM+iY1xUj1ocrRNkMZYA95zkZ2g3zOIfdgKPR+n6Zrks1djLfwBPKMKAR5kny16PsA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CejTOcW6; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CejTOcW6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BF31AC4CEE3; Tue, 15 Jul 2025 05:22:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752556979; bh=LTZ1AAoCssxZeCqtSQnDVFl3TA+mLje+mRQuY/tkaFk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CejTOcW6I2oLSUzYPhxfvN4fGZOrPsRziEGjbcPNvPxegoXD74EcZJiBM67CEts7V /TtNWK+30h51Llmh4opqmufYR15MmEDXbRHggkmK+FjcVcPLvVdUv3E1vSlvtHt3ZR SL8QJSHqxdqQynAH/XZqw9h427Ca2j+ExfIu4cw9DqhNA0+UWV3QxJjXNr2bRlBqnQ Mm2LCqRyYDii6lLWgjhC83FYFpxmvaEOVLFSYi7xhv7Xl0sRzADWCSbNHuxCD+5WkI 4DgOYhZgXdCRreGTrqWYoHiOrEAliCWxOvKtTqzPXM85Q0Pn8gHpWEiEfBeCIKKpU9 ibUikI8JQaDiw== Date: Mon, 14 Jul 2025 22:22:59 -0700 From: "Darrick J. Wong" To: Brian Foster Cc: linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, hch@infradead.org, willy@infradead.org Subject: Re: [PATCH v3 3/7] iomap: optional zero range dirty folio processing Message-ID: <20250715052259.GO2672049@frogsfrogsfrogs> References: <20250714204122.349582-1-bfoster@redhat.com> <20250714204122.349582-4-bfoster@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@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: <20250714204122.349582-4-bfoster@redhat.com> On Mon, Jul 14, 2025 at 04:41:18PM -0400, Brian Foster wrote: > The only way zero range can currently process unwritten mappings > with dirty pagecache is to check whether the range is dirty before > mapping lookup and then flush when at least one underlying mapping > is unwritten. This ordering is required to prevent iomap lookup from > racing with folio writeback and reclaim. > > Since zero range can skip ranges of unwritten mappings that are > clean in cache, this operation can be improved by allowing the > filesystem to provide a set of dirty folios that require zeroing. In > turn, rather than flush or iterate file offsets, zero range can > iterate on folios in the batch and advance over clean or uncached > ranges in between. > > Add a folio_batch in struct iomap and provide a helper for fs' to /me confused by the single quote; is this supposed to read: "...for the fs to populate..."? Either way the code changes look like a reasonable thing to do for the pagecache (try to grab a bunch of dirty folios while XFS holds the mapping lock) so Reviewed-by: "Darrick J. Wong" --D > populate the batch at lookup time. Update the folio lookup path to > return the next folio in the batch, if provided, and advance the > iter if the folio starts beyond the current offset. > > Signed-off-by: Brian Foster > Reviewed-by: Christoph Hellwig > --- > fs/iomap/buffered-io.c | 89 +++++++++++++++++++++++++++++++++++++++--- > fs/iomap/iter.c | 6 +++ > include/linux/iomap.h | 4 ++ > 3 files changed, 94 insertions(+), 5 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index 38da2fa6e6b0..194e3cc0857f 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -750,6 +750,28 @@ static struct folio *__iomap_get_folio(struct iomap_iter *iter, size_t len) > if (!mapping_large_folio_support(iter->inode->i_mapping)) > len = min_t(size_t, len, PAGE_SIZE - offset_in_page(pos)); > > + if (iter->fbatch) { > + struct folio *folio = folio_batch_next(iter->fbatch); > + > + if (!folio) > + return NULL; > + > + /* > + * The folio mapping generally shouldn't have changed based on > + * fs locks, but be consistent with filemap lookup and retry > + * the iter if it does. > + */ > + folio_lock(folio); > + if (unlikely(folio->mapping != iter->inode->i_mapping)) { > + iter->iomap.flags |= IOMAP_F_STALE; > + folio_unlock(folio); > + return NULL; > + } > + > + folio_get(folio); > + return folio; > + } > + > if (folio_ops && folio_ops->get_folio) > return folio_ops->get_folio(iter, pos, len); > else > @@ -811,6 +833,8 @@ static int iomap_write_begin(struct iomap_iter *iter, struct folio **foliop, > int status = 0; > > len = min_not_zero(len, *plen); > + *foliop = NULL; > + *plen = 0; > > if (fatal_signal_pending(current)) > return -EINTR; > @@ -819,6 +843,15 @@ static int iomap_write_begin(struct iomap_iter *iter, struct folio **foliop, > if (IS_ERR(folio)) > return PTR_ERR(folio); > > + /* > + * No folio means we're done with a batch. We still have range to > + * process so return and let the caller iterate and refill the batch. > + */ > + if (!folio) { > + WARN_ON_ONCE(!iter->fbatch); > + return 0; > + } > + > /* > * Now we have a locked folio, before we do anything with it we need to > * check that the iomap we have cached is not stale. The inode extent > @@ -839,6 +872,21 @@ static int iomap_write_begin(struct iomap_iter *iter, struct folio **foliop, > } > } > > + /* > + * The folios in a batch may not be contiguous. If we've skipped > + * forward, advance the iter to the pos of the current folio. If the > + * folio starts beyond the end of the mapping, it may have been trimmed > + * since the lookup for whatever reason. Return a NULL folio to > + * terminate the op. > + */ > + if (folio_pos(folio) > iter->pos) { > + len = min_t(u64, folio_pos(folio) - iter->pos, > + iomap_length(iter)); > + status = iomap_iter_advance(iter, &len); > + if (status || !len) > + goto out_unlock; > + } > + > pos = iomap_trim_folio_range(iter, folio, poffset, &len); > > if (srcmap->type == IOMAP_INLINE) > @@ -1377,6 +1425,12 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero) > if (iter->iomap.flags & IOMAP_F_STALE) > break; > > + /* a NULL folio means we're done with a folio batch */ > + if (!folio) { > + status = iomap_iter_advance_full(iter); > + break; > + } > + > /* warn about zeroing folios beyond eof that won't write back */ > WARN_ON_ONCE(folio_pos(folio) > iter->inode->i_size); > > @@ -1398,6 +1452,26 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero) > return status; > } > > +loff_t > +iomap_fill_dirty_folios( > + struct iomap_iter *iter, > + loff_t offset, > + loff_t length) > +{ > + struct address_space *mapping = iter->inode->i_mapping; > + pgoff_t start = offset >> PAGE_SHIFT; > + pgoff_t end = (offset + length - 1) >> PAGE_SHIFT; > + > + iter->fbatch = kmalloc(sizeof(struct folio_batch), GFP_KERNEL); > + if (!iter->fbatch) > + return offset + length; > + folio_batch_init(iter->fbatch); > + > + filemap_get_folios_dirty(mapping, &start, end, iter->fbatch); > + return (start << PAGE_SHIFT); > +} > +EXPORT_SYMBOL_GPL(iomap_fill_dirty_folios); > + > int > iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero, > const struct iomap_ops *ops, void *private) > @@ -1426,7 +1500,7 @@ iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero, > * flushing on partial eof zeroing, special case it to zero the > * unaligned start portion if already dirty in pagecache. > */ > - if (off && > + if (!iter.fbatch && off && > filemap_range_needs_writeback(mapping, pos, pos + plen - 1)) { > iter.len = plen; > while ((ret = iomap_iter(&iter, ops)) > 0) > @@ -1442,13 +1516,18 @@ iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero, > * if dirty and the fs returns a mapping that might convert on > * writeback. > */ > - range_dirty = filemap_range_needs_writeback(inode->i_mapping, > - iter.pos, iter.pos + iter.len - 1); > + range_dirty = filemap_range_needs_writeback(mapping, iter.pos, > + iter.pos + iter.len - 1); > while ((ret = iomap_iter(&iter, ops)) > 0) { > const struct iomap *srcmap = iomap_iter_srcmap(&iter); > > - if (srcmap->type == IOMAP_HOLE || > - srcmap->type == IOMAP_UNWRITTEN) { > + if (WARN_ON_ONCE(iter.fbatch && > + srcmap->type != IOMAP_UNWRITTEN)) > + return -EIO; > + > + if (!iter.fbatch && > + (srcmap->type == IOMAP_HOLE || > + srcmap->type == IOMAP_UNWRITTEN)) { > s64 status; > > if (range_dirty) { > diff --git a/fs/iomap/iter.c b/fs/iomap/iter.c > index 6ffc6a7b9ba5..89bd5951a6fd 100644 > --- a/fs/iomap/iter.c > +++ b/fs/iomap/iter.c > @@ -9,6 +9,12 @@ > > static inline void iomap_iter_reset_iomap(struct iomap_iter *iter) > { > + if (iter->fbatch) { > + folio_batch_release(iter->fbatch); > + kfree(iter->fbatch); > + iter->fbatch = NULL; > + } > + > iter->status = 0; > memset(&iter->iomap, 0, sizeof(iter->iomap)); > memset(&iter->srcmap, 0, sizeof(iter->srcmap)); > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index 522644d62f30..0b9b460b2873 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h > @@ -9,6 +9,7 @@ > #include > #include > #include > +#include > > struct address_space; > struct fiemap_extent_info; > @@ -239,6 +240,7 @@ struct iomap_iter { > unsigned flags; > struct iomap iomap; > struct iomap srcmap; > + struct folio_batch *fbatch; > void *private; > }; > > @@ -345,6 +347,8 @@ void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len); > bool iomap_dirty_folio(struct address_space *mapping, struct folio *folio); > int iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len, > const struct iomap_ops *ops); > +loff_t iomap_fill_dirty_folios(struct iomap_iter *iter, loff_t offset, > + loff_t length); > int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, > bool *did_zero, const struct iomap_ops *ops, void *private); > int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero, > -- > 2.50.0 > >