group.of.nepali.translators team mailing list archive

[Mathew Hodson <mathew.hodson@xxxxxxxxx>]

** No longer affects: linux (Ubuntu)

** No longer affects: linux (Ubuntu Xenial)

** No longer affects: linux (Ubuntu Bionic)

** No longer affects: linux (Ubuntu Disco)

** No longer affects: linux (Ubuntu Eoan)

** No longer affects: zfs-linux (Ubuntu Bionic)

** No longer affects: zfs-linux (Ubuntu Disco)

** No longer affects: zfs-linux (Ubuntu Eoan)

** Changed in: zfs-linux (Ubuntu)
       Status: Invalid => Fix Released

** Changed in: zfs-linux (Ubuntu)
   Importance: Undecided => Medium

** Changed in: zfs-linux (Ubuntu Xenial)
   Importance: Undecided => Medium

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You received this bug notification because you are a member of नेपाली
भाषा समायोजकहरुको समूह, which is subscribed to Xenial.
Matching subscriptions: Ubuntu 16.04 Bugs
https://bugs.launchpad.net/bugs/1839521

Title:
  Xenial: ZFS deadlock in shrinker path with xattrs

Status in zfs-linux package in Ubuntu:
  Fix Released
Status in zfs-linux source package in Xenial:
  Fix Committed

Bug description:
  [Impact]

   * Xenial's ZFS can deadlock in the memory shrinker path
     after removing files with extended attributes (xattr).

   * Extended attributes are enabled by default, but are
     _not_ used by default, which reduces the likelyhood.

   * It's very difficult/rare to reproduce this problem,
     due to file/xattr/remove/shrinker/lru order/timing
     circumstances required. (weeks for a reporter user)
     but a synthetic test-case has been found for tests.

  [Test Case]

   * A synthetic reproducer is available for this LP,
     with a few steps to touch/setfattr/rm/drop_caches
     plus a kernel module to massage the disposal list.
     (comment #8)

   * In the original ZFS module:
     the xattr dir inode is not purged immediately on
     file removal, but possibly purged _two_ shrinker
     invocations later.  This allows for other thread
     started before file remove to call zfs_zget() on
     the xattr child inode and iput() it, so it makes
     to the same disposal list as the xattr dir inode.
     (comment #3)

   * In the modified ZFS module:
     the xattr dir inode is purged immediately on file
     removal not possibly later on shrinker invocation,
     so the problem window above doesn't exist anymore.
     (comment #12)

  [Regression Potential]

   * Low. The patches are confined to extended attributes
     in ZFS, specifically node removal/purge, and another
     change how an xattr child inode tracks its xattr dir
     (parent) inode, so that it can be purged immediately
     on removal.

   * The ZFS test-suite has been run on original/modified
     zfs-dkms package/kernel modules, with no regressions.
     (comment #11)

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