)]}'
{
  "log": [
    {
      "commit": "b9447ef80bd301b932ac4d85c9622e929de5fd62",
      "tree": "6d0bb1f287ed09f7850b77e2f622c3bebb35112b",
      "parents": [
        "4e06bdd6cbd5105376e7caf4e683ed131e777389"
      ],
      "author": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Mon Mar 09 11:45:38 2009 -0400"
      },
      "committer": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Mon Mar 09 11:45:38 2009 -0400"
      },
      "message": "Btrfs: fix spinlock assertions on UP systems\n\nbtrfs_tree_locked was being used to make sure a given extent_buffer was\nproperly locked in a few places.  But, it wasn\u0027t correct for UP compiled\nkernels.\n\nThis switches it to using assert_spin_locked instead, and renames it to\nbtrfs_assert_tree_locked to better reflect how it was really being used.\n\nSigned-off-by: Chris Mason \u003cchris.mason@oracle.com\u003e\n"
    },
    {
      "commit": "284b066af41579f62649048fdec5c5e7091703e6",
      "tree": "e34185c911cb50b0ade04f804056ffbe2a6e04ae",
      "parents": [
        "42f15d77df8a7e8a2feb15041d5d30710ee7f951"
      ],
      "author": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Mon Feb 09 16:22:03 2009 -0500"
      },
      "committer": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Mon Feb 09 16:22:03 2009 -0500"
      },
      "message": "Btrfs: don\u0027t use spin_is_contended\n\nBtrfs was using spin_is_contended to see if it should drop locks before\ndoing extent allocations during btrfs_search_slot.  The idea was to avoid\nexpensive searches in the tree unless the lock was actually contended.\n\nBut, spin_is_contended is specific to the ticket spinlocks on x86, so this\nis causing compile errors everywhere else.\n\nIn practice, the contention could easily appear some time after we started\ndoing the extent allocation, and it makes more sense to always drop the lock\ninstead.\n\nSigned-off-by: Chris Mason \u003cchris.mason@oracle.com\u003e\n"
    },
    {
      "commit": "b4ce94de9b4d64e8ab3cf155d13653c666e22b9b",
      "tree": "ebc44a9554a50b495b091cb0979d79fd29e50fe7",
      "parents": [
        "c487685d7c18a8481900755aa5c56a7a74193101"
      ],
      "author": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Wed Feb 04 09:25:08 2009 -0500"
      },
      "committer": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Wed Feb 04 09:25:08 2009 -0500"
      },
      "message": "Btrfs: Change btree locking to use explicit blocking points\n\nMost of the btrfs metadata operations can be protected by a spinlock,\nbut some operations still need to schedule.\n\nSo far, btrfs has been using a mutex along with a trylock loop,\nmost of the time it is able to avoid going for the full mutex, so\nthe trylock loop is a big performance gain.\n\nThis commit is step one for getting rid of the blocking locks entirely.\nbtrfs_tree_lock takes a spinlock, and the code explicitly switches\nto a blocking lock when it starts an operation that can schedule.\n\nWe\u0027ll be able get rid of the blocking locks in smaller pieces over time.\nTracing allows us to find the most common cause of blocking, so we\ncan start with the hot spots first.\n\nThe basic idea is:\n\nbtrfs_tree_lock() returns with the spin lock held\n\nbtrfs_set_lock_blocking() sets the EXTENT_BUFFER_BLOCKING bit in\nthe extent buffer flags, and then drops the spin lock.  The buffer is\nstill considered locked by all of the btrfs code.\n\nIf btrfs_tree_lock gets the spinlock but finds the blocking bit set, it drops\nthe spin lock and waits on a wait queue for the blocking bit to go away.\n\nMuch of the code that needs to set the blocking bit finishes without actually\nblocking a good percentage of the time.  So, an adaptive spin is still\nused against the blocking bit to avoid very high context switch rates.\n\nbtrfs_clear_lock_blocking() clears the blocking bit and returns\nwith the spinlock held again.\n\nbtrfs_tree_unlock() can be called on either blocking or spinning locks,\nit does the right thing based on the blocking bit.\n\nctree.c has a helper function to set/clear all the locked buffers in a\npath as blocking.\n\nSigned-off-by: Chris Mason \u003cchris.mason@oracle.com\u003e\n"
    },
    {
      "commit": "65b51a009e29e64c0951f21ea17fdc66bbb0fbd7",
      "tree": "800926527fad4c12ca64083816f33be3d716ec13",
      "parents": [
        "18e35e0ab337ec99c7e03e9ae917745a352c0bb1"
      ],
      "author": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Fri Aug 01 15:11:20 2008 -0400"
      },
      "committer": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Thu Sep 25 11:04:06 2008 -0400"
      },
      "message": "btrfs_search_slot: reduce lock contention by cowing in two stages\n\nA btree block cow has two parts, the first is to allocate a destination\nblock and the second is to copy the old bock over.\n\nThe first part needs locks in the extent allocation tree, and may need to\ndo IO.  This changeset splits that into a separate function that can be\ncalled without any tree locks held.\n\nbtrfs_search_slot is changed to drop its path and start over if it has\nto COW a contended block.  This often means that many writers will\npre-alloc a new destination for a the same contended block, but they\ncache their prealloc for later use on lower levels in the tree.\n\nSigned-off-by: Chris Mason \u003cchris.mason@oracle.com\u003e\n"
    },
    {
      "commit": "925baeddc5b0764a53f2214a1253251bab0e0324",
      "tree": "0e069bf9cc1c4ecd17c812fd1fb81bf807909ee6",
      "parents": [
        "1cc127b5d1b71453091859301de4a7dd6ee96fa8"
      ],
      "author": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Wed Jun 25 16:01:30 2008 -0400"
      },
      "committer": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Thu Sep 25 11:04:03 2008 -0400"
      },
      "message": "Btrfs: Start btree concurrency work.\n\nThe allocation trees and the chunk trees are serialized via their own\ndedicated mutexes.  This means allocation location is still not very\nfine grained.\n\nThe main FS btree is protected by locks on each block in the btree.  Locks\nare taken top / down, and as processing finishes on a given level of the\ntree, the lock is released after locking the lower level.\n\nThe end result of a search is now a path where only the lowest level\nis locked.  Releasing or freeing the path drops any locks held.\n\nSigned-off-by: Chris Mason \u003cchris.mason@oracle.com\u003e\n"
    }
  ]
}