From: Hugh Dickins <hughd@google.com>
To: Allison Henderson <achender@linux.vnet.ibm.com>
Cc: linux-ext4@vger.kernel.org
Subject: punch-hole should go beyond i_size
Date: Wed, 11 Jan 2012 17:02:12 -0800 (PST) [thread overview]
Message-ID: <alpine.LSU.2.00.1201111639240.1833@eggly.anvils> (raw)
Hi Allison,
In thinking about fallocate() on tmpfs, I cross-check with ext4
and find this bug in its implementation of FALLOC_FL_PUNCH_HOLE:
rm -f temp
fallocate -l 4096 temp
du temp # shows 4, right
fallocate -p -l 4096 temp
du temp # shows 0, right
rm -f temp
fallocate -n -l 4096 temp
du temp # shows 4, right
fallocate -p -l 4096 temp
du temp # shows 4, wrong
rm temp
ext4_ext_punch_hole() contains /* No need to punch hole beyond i_size */
early return, and trimming to i_size below, but forgets that the other
variety of fallocate(), with FALLOC_FL_KEEP_SIZE set, may have allocated
blocks beyond i_size. They can be removed with ftruncate(), but it is
unexpected for fallocate() not to undo its own work, and xfs does so.
Hugh
next reply other threads:[~2012-01-12 1:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-12 1:02 Hugh Dickins [this message]
2012-01-12 2:55 ` punch-hole should go beyond i_size Dave Chinner
2012-01-12 16:23 ` Allison Henderson
2012-01-13 0:21 ` Hugh Dickins
2012-01-13 3:18 ` Allison Henderson
2012-05-13 21:13 ` Hugh Dickins
2012-05-15 21:36 ` Allison Henderson
2012-05-15 22:38 ` Hugh Dickins
2012-05-16 6:14 ` Lukáš Czerner
2012-05-16 18:09 ` Hugh Dickins
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