On Tue, Dec 18, 2007 at 10:05:19PM +0000, Hugh Dickins wrote: > Nick has observed that shmem.c still uses GFP_ATOMIC when adding to page > cache or swap cache, without any radix tree preload: so tending to deplete > emergency reserves of memory. > > GFP_ATOMIC remains appropriate in shmem_writepage's add_to_swap_cache: > it's being called under memory pressure, so must not wait for more memory > to become available. But shmem_unuse_inode now has a window in which it > can and should preload with GFP_KERNEL, and say GFP_NOWAIT instead of > GFP_ATOMIC in its add_to_page_cache. > > shmem_getpage is not so straightforward: its filepage/swappage integrity > relies upon exchanging between caches under spinlock, and it would need a > lot of restructuring to place the preloads correctly. Instead, follow > its pattern of retrying on races: use GFP_NOWAIT instead of GFP_ATOMIC in > add_to_page_cache, and begin each circuit of the repeat loop with a sleeping > radix_tree_preload, followed immediately by radix_tree_preload_end - that > won't guarantee success in the next add_to_page_cache, but doesn't need to. > > And we can then remove that bothersome congestion_wait: when needed, > it'll automatically get done in the course of the radix_tree_preload. > > Signed-off-by: Hugh Dickins <[EMAIL PROTECTED]>
Looks good to me. Thanks for this! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
