1$FreeBSD: head/sys/geom/notes 110592 2003-02-09 17:04:57Z phk $
2
3For the lack of a better place to put them, this file will contain
4notes on some of the more intricate details of geom.
5
6-----------------------------------------------------------------------
7Locking of bio_children and bio_inbed
8
9bio_children is used by g_std_done() and g_clone_bio() to keep track

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81"wentbusy" timestamp concurrently.
82
83The statistics data is made available to userland through the use
84of a special allocator (in geom_stats.c) which through a device
85allows userland to mmap(2) the pages containing the statistics data.
86In order to indicate to userland when the data in a statstics
87structure might be inconsistent, g_io_deliver() atomically sets a
88flag "updating" and resets it when the structure is again consistent.