Messages in this thread | | | Date | Thu, 31 Jan 2019 11:17:24 -0500 | From | Dennis Zhou <> | Subject | Re: [PATCH 01/11] btrfs: add macros for compression type and level |
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On Thu, Jan 31, 2019 at 05:00:10PM +0100, David Sterba wrote: > On Mon, Jan 28, 2019 at 04:24:27PM -0500, Dennis Zhou wrote: > > It is very easy to miss places that rely on a certain bitshifting for > > decyphering the type_level overloading. Make macros handle this instead. > > This encoding was a simple way to introduce the combined type and level > for zlib and it could certainly be improved. Either we'll use helpers > like you suggest or add a new structure that contains type and level as > members. That way we'd see where the level still matters and where the > just the type is ok. > > I haven't checked how much intrusive this would be, so that's for later > consideration. Some indirection can be removed for the .set_level > callbacks as it does not necessarily need to be a function so I'm > expecting that the code around that would be touched anyway.
The only user of type_level is btrfs_compress_pages(). I do make an extra call to .set_level() there just to be safe, but that can be taken out as it should be correctly set from when we mounted.
I envisioned .set_level() to be called when setting the compression level of the mount. This can be used in the same place if we were to add per-file compression levels too. I mention later, but an important part of .set_level() is to repurpose the meaning of 0 from meaning use the default to meaning use any workspace available.
Thanks, Dennis
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