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 979D91F03EF for ; Wed, 5 Nov 2025 01:42:34 +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=1762306954; cv=none; b=E9Jt/ynoOmzlVdijhcvXDSed+lpgatXwS57Ljzolyr2gYWprtW2A8HWU2JCooRTOPvixlF6a8uimCKzn8pNLhwrxcMy837HFsKy0I0WPXZjSrFGgaYJNdl7IshtvVIJF2BJn3WH0VE0jLlkosEYipQSYHgJPCWgB1l0hfnjeChI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762306954; c=relaxed/simple; bh=KNuKg5a/kPdE2LMVMwtD7pzUzOoaBdWvRzqGY+Srvi0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Zb9Qv2E1b1MmB65kpsA5mQQQ2X32O/83LAEsy+zGZ0eTgQ8ioLBZbeVQ+94R0dxu9IJvHXHsMR6Iqmi5YaF6kg38DIXRCI2VoAw2KFcdy6eMIKlm+xbUXOUe3YKJVRRsqWJBtlazne8lg0tuTyMUO1wIIPkz4rJPO13J3RqgmuM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YHMeowDl; 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="YHMeowDl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6EC94C116B1; Wed, 5 Nov 2025 01:42:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762306954; bh=KNuKg5a/kPdE2LMVMwtD7pzUzOoaBdWvRzqGY+Srvi0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YHMeowDlUYY8HEI7hwaGp95oTUGhpXyyv6wCQleazGjLRvjB4x83hUPkqOf/0+w1J YeO65qw1zi+8xAxinNaFW/YIJJXdumjkjKjkR4UZQIxAJlKvuNm2wWkBSa0wJPUdEP ahwhkLAs7NzybhVArKPVGXJreEW8xzFsNhUqTiuIxIo9A+bhwdNYFgaxXppHwmpchP pQ9b06H90Ttny9olMrai84QWWLppLKRDmiCPhhYa2AhAZJXcCTgJ7AXJ+bc1Osy4e8 //GCFLIbNtoQa4UN3p6+Gm3mZnG8wJ8GgPaS2P60qpZSoGKfWoUiGjnc1tGxc3rKh/ Po7J6T1CsQAKA== Date: Tue, 4 Nov 2025 17:42:33 -0800 From: "Darrick J. Wong" To: Joanne Koong Cc: brauner@kernel.org, hch@infradead.org, bfoster@redhat.com, linux-fsdevel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v3 7/8] iomap: use find_next_bit() for dirty bitmap scanning Message-ID: <20251105014233.GH196362@frogsfrogsfrogs> References: <20251104205119.1600045-1-joannelkoong@gmail.com> <20251104205119.1600045-8-joannelkoong@gmail.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: <20251104205119.1600045-8-joannelkoong@gmail.com> On Tue, Nov 04, 2025 at 12:51:18PM -0800, Joanne Koong wrote: > Use find_next_bit()/find_next_zero_bit() for iomap dirty bitmap > scanning. This uses __ffs() internally and is more efficient for > finding the next dirty or clean bit than iterating through the bitmap > range testing every bit. > > Signed-off-by: Joanne Koong > Suggested-by: Christoph Hellwig Oh hey, that's a nice cleanup Reviewed-by: "Darrick J. Wong" --D > --- > fs/iomap/buffered-io.c | 61 ++++++++++++++++++++++++++++-------------- > 1 file changed, 41 insertions(+), 20 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index 420fe2865927..3c9a4b773186 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -76,13 +76,34 @@ static void iomap_set_range_uptodate(struct folio *folio, size_t off, > folio_mark_uptodate(folio); > } > > -static inline bool ifs_block_is_dirty(struct folio *folio, > - struct iomap_folio_state *ifs, int block) > +/* > + * Find the next dirty block in the folio. end_blk is inclusive. > + * If no dirty block is found, this will return end_blk + 1. > + */ > +static unsigned ifs_next_dirty_block(struct folio *folio, > + unsigned start_blk, unsigned end_blk) > { > + struct iomap_folio_state *ifs = folio->private; > struct inode *inode = folio->mapping->host; > - unsigned int blks_per_folio = i_blocks_per_folio(inode, folio); > + unsigned int blks = i_blocks_per_folio(inode, folio); > + > + return find_next_bit(ifs->state, blks + end_blk + 1, > + blks + start_blk) - blks; > +} > + > +/* > + * Find the next clean block in the folio. end_blk is inclusive. > + * If no clean block is found, this will return end_blk + 1. > + */ > +static unsigned ifs_next_clean_block(struct folio *folio, > + unsigned start_blk, unsigned end_blk) > +{ > + struct iomap_folio_state *ifs = folio->private; > + struct inode *inode = folio->mapping->host; > + unsigned int blks = i_blocks_per_folio(inode, folio); > > - return test_bit(block + blks_per_folio, ifs->state); > + return find_next_zero_bit(ifs->state, blks + end_blk + 1, > + blks + start_blk) - blks; > } > > static unsigned ifs_find_dirty_range(struct folio *folio, > @@ -94,18 +115,17 @@ static unsigned ifs_find_dirty_range(struct folio *folio, > offset_in_folio(folio, *range_start) >> inode->i_blkbits; > unsigned end_blk = min_not_zero( > offset_in_folio(folio, range_end) >> inode->i_blkbits, > - i_blocks_per_folio(inode, folio)); > - unsigned nblks = 1; > - > - while (!ifs_block_is_dirty(folio, ifs, start_blk)) > - if (++start_blk == end_blk) > - return 0; > + i_blocks_per_folio(inode, folio)) - 1; > + unsigned nblks; > > - while (start_blk + nblks < end_blk) { > - if (!ifs_block_is_dirty(folio, ifs, start_blk + nblks)) > - break; > - nblks++; > - } > + start_blk = ifs_next_dirty_block(folio, start_blk, end_blk); > + if (start_blk > end_blk) > + return 0; > + if (start_blk == end_blk) > + nblks = 1; > + else > + nblks = ifs_next_clean_block(folio, start_blk + 1, end_blk) - > + start_blk; > > *range_start = folio_pos(folio) + (start_blk << inode->i_blkbits); > return nblks << inode->i_blkbits; > @@ -1161,7 +1181,7 @@ static void iomap_write_delalloc_ifs_punch(struct inode *inode, > struct folio *folio, loff_t start_byte, loff_t end_byte, > struct iomap *iomap, iomap_punch_t punch) > { > - unsigned int first_blk, last_blk, i; > + unsigned int first_blk, last_blk; > loff_t last_byte; > u8 blkbits = inode->i_blkbits; > struct iomap_folio_state *ifs; > @@ -1180,10 +1200,11 @@ static void iomap_write_delalloc_ifs_punch(struct inode *inode, > folio_pos(folio) + folio_size(folio) - 1); > first_blk = offset_in_folio(folio, start_byte) >> blkbits; > last_blk = offset_in_folio(folio, last_byte) >> blkbits; > - for (i = first_blk; i <= last_blk; i++) { > - if (!ifs_block_is_dirty(folio, ifs, i)) > - punch(inode, folio_pos(folio) + (i << blkbits), > - 1 << blkbits, iomap); > + while ((first_blk = ifs_next_clean_block(folio, first_blk, last_blk)) > + <= last_blk) { > + punch(inode, folio_pos(folio) + (first_blk << blkbits), > + 1 << blkbits, iomap); > + first_blk++; > } > } > > -- > 2.47.3 > >