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authorChris Mason <chris.mason@oracle.com>2010-12-13 15:06:46 -0500
committerChris Mason <chris.mason@oracle.com>2010-12-13 20:07:01 -0500
commit83a50de97fe96aca82389e061862ed760ece2283 (patch)
tree95421594f180c32cca1ff7f6881f4cf272cf2b5c /usr
parentcd02dca56442e1504fd6bc5b96f7f1870162b266 (diff)
Btrfs: prevent RAID level downgrades when space is low
The extent allocator has code that allows us to fill allocations from any available block group, even if it doesn't match the raid level we've requested. This was put in because adding a new drive to a filesystem made with the default mkfs options actually upgrades the metadata from single spindle dup to full RAID1. But, the code also allows us to allocate from a raid0 chunk when we really want a raid1 or raid10 chunk. This can cause big trouble because mkfs creates a small (4MB) raid0 chunk for data and metadata which then goes unused for raid1/raid10 installs. The allocator will happily wander in and allocate from that chunk when things get tight, which is not correct. The fix here is to make sure that we provide duplication when the caller has asked for it. It does all the dups to be any raid level, which preserves the dup->raid1 upgrade abilities. Signed-off-by: Chris Mason <chris.mason@oracle.com>
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