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Groups > linux.kernel > #1695993

Re: bcache with existing ext4 filesystem

From Theodore Ts'o <tytso@mit.edu>
Newsgroups linux.kernel
Subject Re: bcache with existing ext4 filesystem
Date 2017-07-25 20:10 +0200
Message-ID <u7cro-6ai-13@gated-at.bofh.it> (permalink)
References (2 earlier) <u6R3z-KM-7@gated-at.bofh.it> <u6Rdh-OM-25@gated-at.bofh.it> <u6RPY-1lt-7@gated-at.bofh.it> <u706S-6JM-13@gated-at.bofh.it> <u78nL-3qY-13@gated-at.bofh.it>
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On Tue, Jul 25, 2017 at 03:46:04PM +0200, Pavel Machek wrote:
> 
> Is there some field in ext2 superblock that changes every time
> filesystem is changed? Is mtime changed by fsck/badblocks/...?

No, there isn't.  If we were writing the superblock every time the
file system is changed it would be ***extremely*** flash unfriendly.
It would also be a scalability bottleneck, it would cause us to pay an
extra HDD seek, etc.  So it's a really bad Bad BAD idea, and so we
don't do it.

Cheers,

					- Ted

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Thread

bcache with existing ext4 filesystem Pavel Machek <pavel@ucw.cz> - 2017-07-24 21:00 +0200
  Re: bcache with existing ext4 filesystem Pavel Machek <pavel@ucw.cz> - 2017-07-24 21:20 +0200
    Re: bcache with existing ext4 filesystem Theodore Ts'o <tytso@mit.edu> - 2017-07-24 21:30 +0200
      Re: bcache with existing ext4 filesystem Pavel Machek <pavel@ucw.cz> - 2017-07-24 22:10 +0200
        Re: bcache with existing ext4 filesystem Theodore Ts'o <tytso@mit.edu> - 2017-07-25 07:00 +0200
          Re: bcache with existing ext4 filesystem Pavel Machek <pavel@ucw.cz> - 2017-07-25 08:50 +0200
            Re: bcache with existing ext4 filesystem Vojtech Pavlik <vojtech@ucw.cz> - 2017-07-25 13:10 +0200
              Re: bcache with existing ext4 filesystem Pavel Machek <pavel@ucw.cz> - 2017-07-25 13:20 +0200
                Re: bcache with existing ext4 filesystem Theodore Ts'o <tytso@mit.edu> - 2017-07-25 18:20 +0200
                Re: bcache with existing ext4 filesystem Eric Wheeler <bcache@lists.ewheeler.net> - 2017-07-25 20:20 +0200
                Re: bcache with existing ext4 filesystem Pavel Machek <pavel@ucw.cz> - 2017-07-26 00:10 +0200
                Re: bcache with existing ext4 filesystem Eric Wheeler <bcache@lists.ewheeler.net> - 2017-07-26 19:50 +0200
                Re: bcache with existing ext4 filesystem "Austin S. Hemmelgarn" <ahferroin7@gmail.com> - 2017-07-26 21:10 +0200
                Re: bcache with existing ext4 filesystem Eric Wheeler <bcache@lists.ewheeler.net> - 2017-07-26 21:20 +0200
                Re: bcache with existing ext4 filesystem Pavel Machek <pavel@ucw.cz> - 2017-07-26 22:10 +0200
          Re: bcache with existing ext4 filesystem Pavel Machek <pavel@ucw.cz> - 2017-07-25 15:50 +0200
            Re: bcache with existing ext4 filesystem Theodore Ts'o <tytso@mit.edu> - 2017-07-25 20:10 +0200
              Re: bcache with existing ext4 filesystem Pavel Machek <pavel@ucw.cz> - 2017-07-25 23:00 +0200
  Re: bcache with existing ext4 filesystem Reindl Harald <h.reindl@thelounge.net> - 2017-07-24 21:30 +0200

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