Messages in this thread | | | Date | Wed, 19 Oct 2022 20:17:31 -0700 | From | Ira Weiny <> | Subject | Re: [PATCH v2] erofs: use kmap_local_page() only for erofs_bread() |
| |
On Thu, Oct 20, 2022 at 10:18:36AM +0800, Gao Xiang wrote: > On Wed, Oct 19, 2022 at 08:17:05PM +0200, Fabio M. De Francesco wrote: > > On Wednesday, October 19, 2022 1:36:55 AM CEST Gao Xiang wrote: > > > On Wed, Oct 19, 2022 at 01:21:27AM +0200, Fabio M. De Francesco wrote: > > > > On Tuesday, October 18, 2022 11:29:21 PM CEST Gao Xiang wrote:
[snip]
> > That is not the simple nested unmapped case as you said above, I could take > a very brief example:
Building on this. The uncompressed pages always outnumber the compressed pages, right?
> > 1. map a decompresed page > 2. map a compressed page
First reverse these because you are going to need to map a new decompressed page before another compressed page. So:
1. map compressed 2. map decompressed
Then 4/5 and 7/8 become unmap/map new without issue.
> 3. working > 4. decompressed page is all consumed, unmap the current decompressed page > 5. map the next decompressed page > 6. working > 7. decompressed page is all consumed, unmap the current decompressed page > 8. map the next decompressed page > 9. working
This is more complicated but not overly so.
Simply
9.1 unmap decompressed
> 10. compressed page is all consumed, unmap the current compressed page > 11. map the next compressed page
11.1 remap decompressed
> 12. working > 13. ... (anyway, unmap and remap a compressed page or a decompressed page > in any order.) > > until all process is finished. by using kmap(), it's much simple to > implement this, but kmap_local(), it only complexes the code.
Agreed kmap() is easier but I think this could work.
Basically you keep the compressed mapped first.
I also assume there is also a reverse of this so reverse the pages in that case.
Thoughts? Ira
| |