Messages in this thread | | | Date | Sun, 28 Mar 2010 14:27:53 +0200 | From | Stefan Richter <> | Subject | Re: [GIT, RFC] Killing the Big Kernel Lock |
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Arnd Bergmann wrote: > Your patches look good, but it would be helpful to also set .llseek = no_llseek > in the file operations, because that is much easier to grep for than > only the nonseekable_open. While it's technically a NOP on the presence of > nonseekable_open, it will help that I don't accidentally apply my patch on > top of yours.
Sounds like a plan, but (a) if my .llseek = no_llseek and your .llseek = default_llseek are not within diff context range, you (or whoever else merges mine and yours) only get a compiler warning (Initializer entry defined twice) rather than a merge conflict which couldn't be missed, (b) there won't be a merge conflict in "BKL removal: mark remaining users as 'depends on BKL'". (c) While I don't mind adding more visual clutter to ieee1394/*, I prefer terse coding in firewire/*.
How about I put my nonseekable_open additions into a release branch and send you a pull request after a few days exposure in linux-next? If you do not plan to respin your patch queue soon or at all, I could even let you pull a for-arnd branch with a semantically correct merge of yours and mine.
General thoughts:
".llseek = NULL," so far meant "do the Right Thing on lseek() and friends, as far as the fs core can tell". Shouldn't we keep it that way? It's as close to other ".method = NULL," as it can get, which either mean "silently skip this method if it doesn't matter" (e.g. .flush) or "fail attempts to use this method with a fitting errno" (e.g. .write).
Of course, as we have already seen with infiniband, firewire, ieee1394, .llseek = NULL is ambiguous in practice. Does the driver really want to use default_llseek, or should it rather use no_llseek and/or nonseekable_open, or should it even implement a dummy_llseek() { return 0; } which avoids the BKL but preserves ABI behaviour? This needs to be resolved for each and every case eventually, regardless of whether or when your addition of .llseek = default_llseek enters mainline. -- Stefan Richter -=====-==-=- --== ===-- http://arcgraph.de/sr/
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