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authorSerapheim Dimitropoulos <serapheimd@gmail.com>2019-02-12 10:38:11 -0800
committerBrian Behlendorf <behlendorf1@llnl.gov>2019-02-12 10:38:11 -0800
commit425d3237ee88abc53d8522a7139c926d278b4b7f (patch)
treeb5ac7302fdc38129013399b1dcb63eb8cf1fddb6 /include/libuutil.h
parentd8d418ff0cc90776182534bce10b01e9487b63e4 (diff)
Get rid of space_map_update() for ms_synced_length
Initially, metaslabs and space maps used to be the same thing in ZFS. Later, we started differentiating them by referring to the space map as the on-disk state of the metaslab, making the metaslab a higher-level concept that is metadata that deals with space accounting. Today we've managed to split that code furthermore, with the space map being its own on-disk data structure used in areas of ZFS besides metaslabs (e.g. the vdev-wide space maps used for zpool checkpoint or vdev removal features). This patch refactors the space map code to further split the space map code from the metaslab code. It does so by getting rid of the idea that the space map can have a different in-core and on-disk length (sm_length vs smp_length) which is something that is only used for the metaslab code, and other consumers of space maps just have to deal with. Instead, this patch introduces changes that move the old in-core length of the metaslab's space map to the metaslab structure itself (see ms_synced_length field) while making the space map code only care about the actual space map's length on-disk. The result of this is that space map consumers no longer have to deal with syncing two different lengths for the same structure (e.g. space_map_update() goes away) while metaslab specific behavior stays within the metaslab code. Specifically, the ms_synced_length field keeps track of the amount of data metaslab_load() can read from the metaslab's space map while working concurrently with metaslab_sync() that may be appending to that same space map. As a side note, the patch also adds a few comments around the metaslab code documenting some assumptions and expected behavior. Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8328
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