[Bug 26642] New: Automatically clean dirty bit on ext2/ext4-without-journal file systems

[Bug 26642] New: Automatically clean dirty bit on ext2/ext4-without-journal file systems

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=26642

           Summary: Automatically clean dirty bit on
                    ext2/ext4-without-journal file systems
           Product: File System
           Version: 2.5
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: ext4
        AssignedTo: fs_ext4@kernel-bugs.osdl.org
        ReportedBy: t.artem@mailcity.com
        Regression: No


In ext2/journalless ext4 if you forget to umount the FS before
rebooting/powering down PC you'll have to run fsck on a next boot. That's
obvious.

However we can easily avoid fsck'ing if we clean the dirty bit about a certain
timeout (I suggest a configurable 300 seconds value) and only after dirty
buffers have been flushed to the disk. If we write to the disk again, then this
bit should be set again, of course.

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[Bug 26642] Automatically clean dirty bit on ext2/ext4-without-journal file systems

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https://bugzilla.kernel.org/show_bug.cgi?id=26642


Theodore Tso <tytso@mit.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P1                          |P3
                 CC|                            |tytso@mit.edu




--- Comment #1 from Theodore Tso <tytso@mit.edu>  2011-01-13 18:42:20 ---
This is an old proposal; the challenge which this is that if you do this, we
then have to block any attempts to write to the file system until the dirty bit
has been set in the superblock.   It can be done, but it's not been a high
priority to any of the ext3/ext4 developers.  Patches to do this will be
accepted.  If someone wants more details about how to best do this and is
willing to do the implementation and testing, please let me know.

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[Bug 26642] Automatically clean dirty bit on ext2/ext4-without-journal file systems

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=26642


Andreas Dilger <adilger.kernelbugzilla@dilger.ca> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |adilger.kernelbugzilla@dilg
                   |                            |er.ca




--- Comment #2 from Andreas Dilger <adilger.kernelbugzilla@dilger.ca>  2011-01-13 23:46:56 ---
I would also suggest looking at the per-group dirty bit that Val Henson
developed, maybe 1.5 years ago.  This allowed e2fsck to limit its boot-time
scanning to only the small subset of groups/inodes that were modified shortly
before the crash.

I don't know how close to production-ready that code was, but it was at least
at the working prototype stage.  Some changes and updates are probably needed
(e.g. changing the per-group flag value to avoid conflicting with other
assigned flags) before using it on a newer kernel with ext4.

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[Bug 26642] Automatically clean dirty bit on ext2/ext4-without-journal file systems

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https://bugzilla.kernel.org/show_bug.cgi?id=26642





--- Comment #3 from Theodore Tso <tytso@mit.edu>  2011-01-14 03:23:55 ---
I didn't think Val had any code that was anywhere near working.

As far as I know she never got around the design problem of what to do when you
have a big file where the inode is in group #1, but it needs blocks in block
groups #1, #2, #3, #4.... and what to do when you have a directory which has
directory blocks that spans multiple block groups.

She was going to design something complete new and incompatible from a format
perspective, that had bidirection pointers, but I don't think this ever got to
a working prototype stage as far as I know.  Feel free to ask her, though....

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[Bug 26642] Automatically clean dirty bit on ext2/ext4-without-journal file systems

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https://bugzilla.kernel.org/show_bug.cgi?id=26642


Alan <alan@lxorguk.ukuu.org.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |alan@lxorguk.ukuu.org.uk
         Resolution|                            |OBSOLETE




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[Bug 26642] Automatically clean dirty bit on ext2/ext4-without-journal file systems

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--- Comment #4 from Artem S. Tashkinov <t.artem@mailcity.com>  2012-08-14 15:41:14 ---
Is it obsolete because no one wants to implement this feature or because Alan
Cox thinks this feature request is meaningless?

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[Bug 26642] Automatically clean dirty bit on ext2/ext4-without-journal file systems

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https://bugzilla.kernel.org/show_bug.cgi?id=26642





--- Comment #5 from Alan <alan@lxorguk.ukuu.org.uk>  2012-08-14 18:33:23 ---
It is obsolete because nobody has touched the bug for well over a year.

The place to discuss it further and send patches is the mailing list

(I'd love per inode group dirt bits!)

Alan

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