)]}'
{
  "log": [
    {
      "commit": "bd56b30205bc09da0beb80d4ba3d4c7309792da5",
      "tree": "a5cb3104687b27e923b73b2840f053abc1229a92",
      "parents": [
        "b4ce94de9b4d64e8ab3cf155d13653c666e22b9b"
      ],
      "author": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Wed Feb 04 09:27:02 2009 -0500"
      },
      "committer": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Wed Feb 04 09:27:02 2009 -0500"
      },
      "message": "Btrfs: Make btrfs_drop_snapshot work in larger and more efficient chunks\n\nEvery transaction in btrfs creates a new snapshot, and then schedules the\nsnapshot from the last transaction for deletion.  Snapshot deletion\nworks by walking down the btree and dropping the reference counts\non each btree block during the walk.\n\nIf if a given leaf or node has a reference count greater than one,\nthe reference count is decremented and the subtree pointed to by that\nnode is ignored.\n\nIf the reference count is one, walking continues down into that node\nor leaf, and the references of everything it points to are decremented.\n\nThe old code would try to work in small pieces, walking down the tree\nuntil it found the lowest leaf or node to free and then returning.  This\nwas very friendly to the rest of the FS because it didn\u0027t have a huge\nimpact on other operations.\n\nBut it wouldn\u0027t always keep up with the rate that new commits added new\nsnapshots for deletion, and it wasn\u0027t very optimal for the extent\nallocation tree because it wasn\u0027t finding leaves that were close together\non disk and processing them at the same time.\n\nThis changes things to walk down to a level 1 node and then process it\nin bulk.  All the leaf pointers are sorted and the leaves are dropped\nin order based on their extent number.\n\nThe extent allocation tree and commit code are now fast enough for\nthis kind of bulk processing to work without slowing the rest of the FS\ndown.  Overall it does less IO and is better able to keep up with\nsnapshot deletions under high load.\n\nSigned-off-by: Chris Mason \u003cchris.mason@oracle.com\u003e\n"
    },
    {
      "commit": "d352ac68148b69937d39ca5d48bcc4478e118dbf",
      "tree": "7951dd7311999d9e77766acdc7f8e93de97874d8",
      "parents": [
        "9a5e1ea1e1e539e244a54afffc330fc368376ab9"
      ],
      "author": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Mon Sep 29 15:18:18 2008 -0400"
      },
      "committer": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Mon Sep 29 15:18:18 2008 -0400"
      },
      "message": "Btrfs: add and improve comments\n\nThis improves the comments at the top of many functions.  It didn\u0027t\ndive into the guts of functions because I was trying to\navoid merging problems with the new allocator and back reference work.\n\nextent-tree.c and volumes.c were both skipped, and there is definitely\nmore work todo in cleaning and commenting the code.\n\nSigned-off-by: Chris Mason \u003cchris.mason@oracle.com\u003e\n"
    },
    {
      "commit": "e465768938f95388723b0fd3c50a0ae48173edb9",
      "tree": "0f624a9a98dedfafae902e12b384d27e1100cd3a",
      "parents": [
        "e8569813849b5da394a195c7e76b4faa452b12d1"
      ],
      "author": {
        "name": "Zheng Yan",
        "email": "zheng.yan@oracle.com",
        "time": "Fri Sep 26 10:04:53 2008 -0400"
      },
      "committer": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Fri Sep 26 10:04:53 2008 -0400"
      },
      "message": "Btrfs: Add shared reference cache\n\nBtrfs has a cache of reference counts in leaves, allowing it to\navoid reading tree leaves while deleting snapshots.  To reduce\ncontention with multiple subvolumes, this cache is private to each\nsubvolume.\n\nThis patch adds shared reference cache support. The new space\nbalancing code plays with multiple subvols at the same time, So\nthe old per-subvol reference cache is not well suited.\n\nSigned-off-by: Chris Mason \u003cchris.mason@oracle.com\u003e\n"
    },
    {
      "commit": "bcc63abbf3e9bf948a1b0129b3e6120ec7d7f698",
      "tree": "1c66dc210f948f79c86786368d2c75b57482875d",
      "parents": [
        "33958dc6d38fb4ca7e62273855fcb2db7e616263"
      ],
      "author": {
        "name": "Yan",
        "email": "zheng.yan@oracle.com",
        "time": "Wed Jul 30 16:29:20 2008 -0400"
      },
      "committer": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Thu Sep 25 11:04:05 2008 -0400"
      },
      "message": "Btrfs: implement memory reclaim for leaf reference cache\n\nThe memory reclaiming issue happens when snapshot exists. In that\ncase, some cache entries may not be used during old snapshot dropping,\nso they will remain in the cache until umount.\n\nThe patch adds a field to struct btrfs_leaf_ref to record create time. Besides,\nthe patch makes all dead roots of a given snapshot linked together in order of\ncreate time. After a old snapshot was completely dropped, we check the dead\nroot list and remove all cache entries created before the oldest dead root in\nthe list.\n\nSigned-off-by: Chris Mason \u003cchris.mason@oracle.com\u003e\n"
    },
    {
      "commit": "017e5369eb353559d68a11d4a718faa634533821",
      "tree": "c339f2f4a59e403c7f9bfa8d137663c6bf260537",
      "parents": [
        "31153d81284934601d08110ac7698fd9a535e4c0"
      ],
      "author": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Mon Jul 28 15:32:51 2008 -0400"
      },
      "committer": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Thu Sep 25 11:04:05 2008 -0400"
      },
      "message": "Btrfs: Leaf reference cache update\n\nThis changes the reference cache to make a single cache per root\ninstead of one cache per transaction, and to key by the byte number\nof the disk block instead of the keys inside.\n\nThis makes it much less likely to have cache misses if a snapshot\nor something has an extra reference on a higher node or a leaf while\nthe first transaction that added the leaf into the cache is dropping.\n\nSome throttling is added to functions that free blocks heavily so they\nwait for old transactions to drop.\n\nSigned-off-by: Chris Mason \u003cchris.mason@oracle.com\u003e\n"
    },
    {
      "commit": "31153d81284934601d08110ac7698fd9a535e4c0",
      "tree": "38f873fea3012a58d2a8f4d439a9546443617878",
      "parents": [
        "3a115f520f391b4ab14041bdd6eedb370d944fa6"
      ],
      "author": {
        "name": "Yan Zheng",
        "email": "zheng.yan@oracle.com",
        "time": "Mon Jul 28 15:32:19 2008 -0400"
      },
      "committer": {
        "name": "Chris Mason",
        "email": "chris.mason@oracle.com",
        "time": "Thu Sep 25 11:04:05 2008 -0400"
      },
      "message": "Btrfs: Add a leaf reference cache\n\nMuch of the IO done while dropping snapshots is done looking up\nleaves in the filesystem trees to see if they point to any extents and\nto drop the references on any extents found.\n\nThis creates a cache so that IO isn\u0027t required.\n\nSigned-off-by: Chris Mason \u003cchris.mason@oracle.com\u003e\n"
    }
  ]
}