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From: Matthew Wilcox <willy@infradead.org>
To: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Cc: linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk,
	linux-kernel@vger.kernel.org, pali@kernel.org, dsterba@suse.cz,
	aaptel@suse.com, rdunlap@infradead.org, joe@perches.com,
	mark@harmstone.com, nborisov@suse.com,
	linux-ntfs-dev@lists.sourceforge.net, anton@tuxera.com,
	dan.carpenter@oracle.com, hch@lst.de, ebiggers@kernel.org,
	andy.lavr@gmail.com, kari.argillander@gmail.com,
	oleksandr@natalenko.name
Subject: Re: [PATCH v27 02/10] fs/ntfs3: Add initialization of super block
Date: Thu, 29 Jul 2021 16:59:00 +0100	[thread overview]
Message-ID: <YQLQRGyKGdL00sQ7@casper.infradead.org> (raw)
In-Reply-To: <20210729134943.778917-3-almaz.alexandrovich@paragon-software.com>

On Thu, Jul 29, 2021 at 04:49:35PM +0300, Konstantin Komarov wrote:
> +static void ntfs_readahead(struct readahead_control *rac)
> +{
> +	struct address_space *mapping = rac->mapping;
> +	struct inode *inode = mapping->host;
> +	struct ntfs_inode *ni = ntfs_i(inode);
> +	u64 valid;
> +	loff_t pos;
> +
> +	if (is_resident(ni)) {
> +		/* no readahead for resident */
> +		return;
> +	}
> +
> +	if (is_compressed(ni)) {
> +		/* no readahead for compressed */
> +		return;

I'm sure this works, but it could perform better ;-)

The ->readpage path that you fall back to is synchronous (unless I
misunderstand something).  We now have readahead_expand() which lets
you ensure that there are pages in the page cache for the entire
range of the compressed extent.  So if you can create an asynchronous
decompression path (probably need your own custom bi_end_io), you can
start reads here and only unlock the pages after you've done the
decompression.

This should not gate your code being accepted upstream.  What I'd
really like to see is your buffered i/o path being converted from
buffer_heads to iomap, and iomap to gain the ability to handle
compressed extents.

> +	valid = ni->i_valid;
> +	pos = readahead_pos(rac);
> +
> +	if (valid < i_size_read(inode) && pos <= valid &&
> +	    valid < pos + readahead_length(rac)) {
> +		/* range cross 'valid'. read it page by page */
> +		return;

This, I do not understand.  Why can't ntfs_get_block / mpage_readahead
cope with a readahead that crosses i_valid?  AIUI, i_valid is basically
the same as i_size, and mpage_readahead() handles crossing i_size
just fine.


  reply	other threads:[~2021-07-29 16:01 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29 13:49 [PATCH v27 00/10] NTFS read-write driver GPL implementation by Paragon Software Konstantin Komarov
2021-07-29 13:49 ` [PATCH v27 01/10] fs/ntfs3: Add headers and misc files Konstantin Komarov
2021-07-29 13:49 ` [PATCH v27 02/10] fs/ntfs3: Add initialization of super block Konstantin Komarov
2021-07-29 15:59   ` Matthew Wilcox [this message]
2021-07-30  8:28   ` Christophe JAILLET
2021-08-10  9:02   ` Christoph Hellwig
2021-07-29 13:49 ` [PATCH v27 03/10] fs/ntfs3: Add bitmap Konstantin Komarov
2021-07-30  8:11   ` Christophe JAILLET
2021-07-29 13:49 ` [PATCH v27 04/10] fs/ntfs3: Add file operations and implementation Konstantin Komarov
2021-07-30  7:40   ` Christophe JAILLET
2021-08-22 12:20   ` Pali Rohár
2021-08-22 14:31     ` Kari Argillander
2021-08-24 11:33       ` Pali Rohár
2021-07-29 13:49 ` [PATCH v27 05/10] fs/ntfs3: Add attrib operations Konstantin Komarov
2021-07-30  7:30   ` Christophe JAILLET
2021-07-29 13:49 ` [PATCH v27 06/10] fs/ntfs3: Add compression Konstantin Komarov
2021-07-29 13:49 ` [PATCH v27 07/10] fs/ntfs3: Add NTFS journal Konstantin Komarov
2021-07-30  8:06   ` Christophe JAILLET
2021-07-29 13:49 ` [PATCH v27 08/10] fs/ntfs3: Add Kconfig, Makefile and doc Konstantin Komarov
2021-08-10  7:47   ` Kari Argillander
2021-08-10  8:19     ` Pali Rohár
2021-08-10  8:46       ` Kari Argillander
2021-07-29 13:49 ` [PATCH v27 09/10] fs/ntfs3: Add NTFS3 in fs/Kconfig and fs/Makefile Konstantin Komarov
2021-07-29 13:49 ` [PATCH v27 10/10] fs/ntfs3: Add MAINTAINERS Konstantin Komarov
2021-08-09 10:56   ` David Sterba
2021-08-09 16:16     ` Konstantin Komarov
2021-08-09 16:44       ` Kari Argillander
2021-08-09 16:54         ` Randy Dunlap
2021-08-09 18:56           ` Dan Williams
2021-08-09 19:45             ` Kari Argillander
2021-07-29 16:24 ` [PATCH v27 00/10] NTFS read-write driver GPL implementation by Paragon Software Darrick J. Wong
2021-08-02  3:23   ` Theodore Ts'o
2021-08-02 15:05     ` Theodore Ts'o
2021-08-12 17:03     ` Kari Argillander
2021-08-13 15:53       ` Kari Argillander
2021-08-21 12:38     ` Yan Pashkovsky
2021-08-03 11:57 ` [PATCH] Restyle comments to better align with kernel-doc Kari Argillander
2021-08-03 13:38   ` Dan Carpenter
2021-08-03 15:26     ` Kari Argillander
2021-08-03 15:41       ` Matthew Wilcox
2021-08-30 16:10   ` Konstantin Komarov
2021-08-30 17:13     ` Kari Argillander
2021-08-10  5:46 ` [PATCH v27 00/10] NTFS read-write driver GPL implementation by Paragon Software Kari Argillander
2021-08-10  6:47   ` Darrick J. Wong

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