On Thu, Jun 25, 2009 at 08:47:59AM -0400, Greg Freemyer wrote:

Aneesh,

Can you provide the below requested info?

Thanks
Greg

On Tue, Jun 23, 2009 at 8:11 PM, Andreas Dilger[off-list ref] wrote:

quoted

On Jun 23, 2009  20:02 -0400, Greg Freemyer wrote:

quoted

On Tue, Jun 23, 2009 at 7:19 PM, Andreas Dilger[off-list ref] wrote:

quoted

On Jun 23, 2009  17:25 +0900, Akira Fujita wrote:

quoted

alloc_flag of ext4_alloc_rule structure is set as "mandatory" or "advisory".
Restricted blocks with "mandatory" are never used by block allocator.
But in "advisory" case, block allocator is allowed to use restricted blocks
when there are no free blocks on FS.

Would it make more sense to implement the range protections via the
existing preallocation ranges (PA)?  An inode can have multiple
PAs attached to it to have it prefer allocations from that range.

We could also attach PAs to the superblock to prevent other files from
allocating out of those ranges.  This would work better with the existing
allocation code instead of creating a second similar mechanism.

Where can I find documentation about how PA works?  Or is it just in
the source?  If so, what are one or two calls that cause the PA ranges
to be set, etc.

Mostly the source. Some of mballoc details are documented in the ols
2008 paper. Regarding some of the functions

ext4_mb_use_preallocated -> allocate from PA
ext4_mb_new_preallocation -> Create new PA.

Source code also have some documentation that explains how mballoc use
PA.

-aneesh
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