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Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks

From "Martin K. Petersen" <martin.petersen@oracle.com>
Newsgroups linux.kernel
Subject Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks
Date 2016-03-03 19:10 +0100
Message-ID <r8FRh-2vI-7@gated-at.bofh.it> (permalink)
References <r86qt-2pO-3@gated-at.bofh.it> <r86qt-2pO-5@gated-at.bofh.it> <r8ka6-3CZ-7@gated-at.bofh.it> <r8nUm-6fn-19@gated-at.bofh.it> <r8oQq-6Vq-13@gated-at.bofh.it>
Organization Oracle Corporation

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>>>>> "Linus" == Linus Torvalds <torvalds@linux-foundation.org> writes:

Linus> .. but the flag doesn't even set that. Even if you avoid TRIM,
Linus> there is absolutely zero guarantees that WRITE_SAME would do
Linus> "real storage blocks full of zeroes backing the LBAs they just
Linus> wrote out".

That's not entirely true. Writing the blocks may cause them to be
allocated on the storage device (depending on which flags we feed it in
WRITE SAME).

The filesystems people were wanted the following semantics:

 - deallocate, don't care about contents for future reads (discard)
 - deallocate, guarantee zeroes on future reads (zeroout)
 - (re)allocate, guarantee zeroes on future reads (zeroout)

Maybe we just need a better naming scheme...

-- 
Martin K. Petersen	Oracle Linux Engineering

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Thread

[PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page cache "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-02 05:20 +0100
  [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-02 05:20 +0100
    Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Christoph Hellwig <hch@infradead.org> - 2016-03-02 10:30 +0100
    Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-02 20:00 +0100
      Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-03 00:00 +0100
        Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-03 01:00 +0100
          Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-03 18:10 +0100
            Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-03 19:00 +0100
              Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Christoph Hellwig <hch@infradead.org> - 2016-03-03 19:10 +0100
              Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks "Martin K. Petersen" <martin.petersen@oracle.com> - 2016-03-03 19:20 +0100
              Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-03 19:30 +0100
          Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks "Martin K. Petersen" <martin.petersen@oracle.com> - 2016-03-03 19:10 +0100
            Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Christoph Hellwig <hch@infradead.org> - 2016-03-03 19:10 +0100
              Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-03 19:20 +0100
              Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks "Martin K. Petersen" <martin.petersen@oracle.com> - 2016-03-03 20:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-03 23:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-04 00:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-04 01:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-04 00:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Thomas Schoebel-Theuer <tst@schoebel-theuer.de> - 2016-03-04 03:40 +0100
            Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-03 19:20 +0100
  Re: [PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page cache Arnd Bergmann <arnd@arndb.de> - 2016-03-02 10:20 +0100
    Re: [PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page  cache Christoph Hellwig <hch@infradead.org> - 2016-03-02 10:50 +0100
      Re: [PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page cache Arnd Bergmann <arnd@arndb.de> - 2016-03-02 12:00 +0100

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