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From: Filipe Manana <fdmanana@gmail.com>
To: linux-ext4 <linux-ext4@vger.kernel.org>
Subject: RWF_NOWAIT writes not failing when writing to a range with holes
Date: Mon, 15 Jun 2020 18:53:11 +0100	[thread overview]
Message-ID: <CAL3q7H4boq-Rsm+OSK5bSBJhu-ywugOdwWfHRQkyuyDC_RoRZA@mail.gmail.com> (raw)

Hi,

I found out a bug in btrfs where a RWF_NOWRITE does not fail if we
write to a range that starts with an extent followed by holes (since
it requires allocating extent(s)).

When writing a test case for fstests I noticed xfs fails with -EAGAIN
as expected, but ext4 succeeds just like btrfs currently does:

mkfs.ext4 -F /dev/sdb
mount /dev/sdb /mnt

xfs_io -f -d -c "pwrite -S 0xab -b 256K 0 256K" /mnt/bar
xfs_io -c "fpunch 64K 64K" /mnt/bar
sync
xfs_io -d -c "pwrite -N -V 1 -b 128K -S 0xfe 0 128K" /mnt/bar

Is this a known bug? Or is there a technical reason that makes it too
expensive to check no extents will need to be allocated?

Thanks.

-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”

             reply	other threads:[~2020-06-15 17:53 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-15 17:53 Filipe Manana [this message]
2020-07-08 14:17 ` RWF_NOWAIT writes not failing when writing to a range with holes Jan Kara
2020-10-15 15:37   ` Filipe Manana

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