Messages in this thread | | | Date | Fri, 2 Mar 2012 12:39:57 +0000 | Subject | ext4 bug? last write time precedes last mount time on a writable volume! | From | Neil Clarkson <> |
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Isn't the s_wtime field of the ext4 superblock supposed to show the time, in seconds since the epoch, of the last write? It isn't happening!
This line suggests the s_wtime is updated on a superblock commit unless the volume is read only.
static int ext4_commit_super(struct super_block *sb, int sync)'
/* * If the file system is mounted read-only, don't update the * superblock write time. This avoids updating the superblock * write time when we are mounting the root file system * read/only but we need to replay the journal; at that point, * for people who are east of GMT and who make their clock * tick in localtime for Windows bug-for-bug compatibility, * the clock is set in the future, and this will cause e2fsck * to complain and force a full file system check. */ if (!(sb->s_flags & MS_RDONLY)) es->s_wtime = cpu_to_le32(get_seconds());
Yet a dumpe2fs on my ubuntu box gives the output below. Last write time just a half hour after the volume was created!
Filesystem created: Wed Nov 23 13:42:18 2011 Last mount time: Tue Feb 21 09:07:54 2012 Last write time: Wed Nov 23 14:12:57 2011
/dev/sda1 on / type ext4 (rw,errors=remount-ro,commit=0)
Linux Wallace 3.0.0-16-generic #28-Ubuntu SMP Fri Jan 27 17:44:39 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux (Ubuntu 11.10)
OpenSuse and Fedora show something slightly different, but still wrong: last write time same as last mount time.
Linux VM-OpenSUSE2 2.6.37.1-1.2-desktop #1 SMP PREEMPT 2011-02-21 10:34:10 +0100 x86_64 x86_64 x86_64 GNU/Linux (Open SUSE 11.4)
Filesystem created: Fri Sep 23 18:04:27 2011 Last mount time: Fri Jan 27 09:34:55 2012 Last write time: Fri Jan 27 09:34:55 2012
Linux fedoraVM 2.6.35.6-45.fc14.i686 #1 SMP Mon Oct 18 23:56:17 UTC 2010 i686 i686 i386 GNU/Linux (Fedora 14)
Filesystem created: Wed Nov 3 07:24:17 2010 Last mount time: Fri Feb 3 13:04:41 2012 Last write time: Fri Feb 3 13:04:41 2012
Could someone please help me understand this? If this isn't the correct forum to be querying apparently wayward ext4 functionality, please point me at a better one.
Neil Clarkson -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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