> > Frustratingly, gfp_t is really divided into two classes of flags. One are the > > context dependent ones (can we sleep? can we enter filesystem? block subsystem? > > should we use some extra reserves, etc.). The other ones are the type of memory > > required and depend on how the algorithm is implemented rather than the point > > at which the memory is allocated (highmem? dma memory? etc). > > > > Some of functions which allocate a page and add it to page cache take a gfp_t, > > but sometimes those functions or their callers aren't really doing the right > > thing: when allocating pagecache page, the memory type should be > > mapping_gfp_mask(mapping). When allocating radix tree nodes, the memory type > > should be kernel mapped (not highmem) memory. The gfp_t argument should only > > really be needed for context dependent options. > > > > This patch doesn't really solve that tangle in a nice way, but it does attempt > > to fix a couple of bugs. find_or_create_page changes its radix-tree allocation > > to only include the main context dependent flags in order so the pagecache > > page may be allocated from arbitrary types of memory without affecting the > > radix-tree. Then grab_cache_page_nowait() is changed to allocate radix-tree > > nodes with GFP_NOFS, because it is not supposed to reenter the filesystem. > > > > Filesystems should be careful about exactly what semantics they want and what > > they get when fiddling with gfp_t masks to allocate pagecache. One should be > > as liberal as possible with the type of memory that can be used, and same > > for the the context specific flags. > > > > Signed-off-by: Nick Piggin <npiggin@xxxxxxx> > > Looks good to me. > > Reviewed-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx> me too. Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
