From: Hugh Dickins Date: Tue, 5 Feb 2008 06:28:54 +0000 (-0800) Subject: tmpfs: radix_tree_preloading X-Git-Tag: v2.6.25-rc1~961 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b409f9fcf04692c0f603d28c73d2e3dfed27bf54;p=pandora-kernel.git tmpfs: radix_tree_preloading 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 Looks-good-to: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed