linux-kernel - Re: [RFC 0/7] ext4: Allocator changes for atomic write support with DIO

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Message-ID: <ZXlSR8CTXjkeKxwk@li-bb2b2a4c-3307-11b2-a85c-8fa5c3a69313.ibm.com>
Date:   Wed, 13 Dec 2023 12:12:15 +0530
From:   Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To:     John Garry <john.g.garry@...cle.com>
Cc:     linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>,
        Ritesh Harjani <ritesh.list@...il.com>,
        linux-kernel@...r.kernel.org,
        "Darrick J . Wong" <djwong@...nel.org>,
        linux-block@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, dchinner@...hat.com
Subject: Re: [RFC 0/7] ext4: Allocator changes for atomic write support with
 DIO

On Mon, Dec 11, 2023 at 04:24:14PM +0530, Ojaswin Mujoo wrote:
> > > > looks ok so far, then write 4KB at offset 0:
> > > > 
> > > > # /test-pwritev2 -a -d -p 0 -l 4096  /root/mnt/file
> > > > file=/root/mnt/file write_size=4096 offset=0 o_flags=0x4002 wr_flags=0x24
> > 
> > ...
> > 
> > > > Please note that I tested on my own dev branch, which contains changes over
> > > > [1], but I expect it would not make a difference for this test.
> > > Hmm this should not ideally happen, can you please share your test
> > > script with me if possible?
> > 
> > It's doing nothing special, just RWF_ATOMIC flag is set for DIO write:
> > 
> > https://github.com/johnpgarry/linux/blob/236870d48ecb19c1cf89dc439e188182a0524cd4/samples/vfs/test-pwritev2.c
> 
> Thanks for the script, will try to replicate this today and get back to
> you.
> 

Hi John,

So I don't seem to be able to hit the warn on:

$ touch mnt/testfile
$ ./test-pwritev2 -a -d -p 0 -l 4096 mnt/testfile

	file=mnt/testfile write_size=4096 offset=0 o_flags=0x4002 wr_flags=0x24
	main wrote 4096 bytes at offset 0

$ filefrag -v mnt/testfile

	Filesystem type is: ef53
	File size of testfile is 4096 (1 block of 4096 bytes)
	ext:     logical_offset:        physical_offset: length:   expected: flags:
		0:        0..       0:      32900..     32900:      1: last,eof

$ ./test-pwritev2 -a -d -p 8192 -l 8192 mnt/testfile

	file=mnt/testfile write_size=8192 offset=8192 o_flags=0x4002 wr_flags=0x24
	main wrote 8192 bytes at offset 8192

$ filefrag -v mnt/testfile

	Filesystem type is: ef53
	File size of mnt/testfile is 16384 (4 blocks of 4096 bytes)
	 ext:     logical_offset:        physical_offset: length:   expected: flags:
		0:        0..       0:      32900..     32900:      1:
		1:        2..       3:      33288..     33289:      2: 32902: last,eof
	mnt/testfile: 2 extents found

Not sure why you are hitting the WARN_ON. The tree I used is:

Latest ted/dev + your atomic patchset v1 + this patchset

Regards,
ojaswin