On Fri, 2011-04-01 at 00:51 +0200, Michal Nazarewicz wrote: > On Fri, 01 Apr 2011 00:26:51 +0200, Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> > wrote: > >> Bug in the above place does not mean that we could not allocate > >> memory. It means caller is broken. > > > > Could you explain that a bit? > > > > Is this a case where a device is mapped to a very *specific* range of > > physical memory and no where else? What are the reasons for not marking > > it off limits at boot? I also saw some bits of isolation and migration > > in those patches. Can't the migration fail? > > The function is called from alloc_contig_range() (see patch 05/12) which > makes sure that the PFN is valid. Situation where there is not enough > space is caught earlier in alloc_contig_range(). > > alloc_contig_freed_pages() must be given a valid PFN range such that all > the pages in that range are free (as in are within the region tracked by > page allocator) and of MIGRATETYPE_ISOLATE so that page allocator won't > touch them. OK, so it really is a low-level function only. How about a comment that explicitly says this? "Only called from $FOO with the area already isolated." It probably also deserves an __ prefix. > That's why invalid PFN is a bug in the caller and not an exception that > has to be handled. > > Also, the function is not called during boot time. It is called while > system is already running. What kind of success have you had running this in practice? I'd be worried that some silly task or a sticky dentry would end up in the range that you want to allocate in. -- Dave -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
