Re: [PATCH 1/4] Btrfs: use radix tree for checksum

On 07/06/2012 11:37 PM, Chris Mason wrote:

On Wed, Jun 13, 2012 at 07:50:52PM -0600, Liu Bo wrote:

quoted

On 06/14/2012 12:07 AM, Zach Brown wrote:

quoted

quoted

  int set_state_private(struct extent_io_tree *tree, u64 start, u64
private)
  {

[...]

quoted

+    ret = radix_tree_insert(&tree->csum, (unsigned long)start,
+                   (void *)((unsigned long)private<<  1));

Will this fail for 64bit files on 32bit hosts?

In theory it will fail, but crc32c return u32, so private will be originally u32,
and it'd be ok on 32bit hosts.

The (unsigned long)start part looks wrong though.  This is the byte offset
from 0, so on a 32 bit machine you won't be able to have large files.

The page cache also has this limitation, but it gains extra bits
counting page indexes instead of byte indexes.

I see.

I've made that change here and I'm benchmarking it on my big flash ;)

Thanks a lot. :)

I must note that this patchset is still very initial, and this week I've fixed
a deadlock bug hidden in the 4th patch (it can be triggered by xfstests 208).

I'm planning to set up a worker thread or just use 'endio_meta' thread for merge_state
and do more tuning work to lessen writer lock.

thanks,
liubo

-chris
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