From 3dbb5eb9a3aa04f40e551338eee5e8d06f352fe8 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Wed, 3 Jun 2015 09:32:39 -0400 Subject: ext4 crypto: allocate bounce pages using GFP_NOWAIT Previously we allocated bounce pages using a combination of alloc_page() and mempool_alloc() with the __GFP_WAIT bit set. Instead, use mempool_alloc() with GFP_NOWAIT. The mempool_alloc() function will try using alloc_pages() initially, and then only use the mempool reserve of pages if alloc_pages() is unable to fulfill the request. This minimizes the the impact on the mm layer when we need to do a large amount of writeback of encrypted files, as Jaeguk Kim had reported that under a heavy fio workload on a system with restricted amounts memory (which unfortunately, includes many mobile handsets), he had observed the the OOM killer getting triggered several times. Using GFP_NOWAIT If the mempool_alloc() function fails, we will retry the page writeback at a later time; the function of the mempool is to ensure that we can writeback at least 32 pages at a time, so we can more efficiently dispatch I/O under high memory pressure situations. In the future we should make this be a tunable so we can determine the best tradeoff between permanently sequestering memory and the ability to quickly launder pages so we can free up memory quickly when necessary. Signed-off-by: Theodore Ts'o --- fs/ext4/crypto.c | 27 ++++++--------------------- 1 file changed, 6 insertions(+), 21 deletions(-) (limited to 'fs/ext4/crypto.c') diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c index efcb7c04d172..f5c82e8b7b5c 100644 --- a/fs/ext4/crypto.c +++ b/fs/ext4/crypto.c @@ -71,12 +71,8 @@ void ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx) { unsigned long flags; - if (ctx->flags & EXT4_WRITE_PATH_FL && ctx->w.bounce_page) { - if (ctx->flags & EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL) - __free_page(ctx->w.bounce_page); - else - mempool_free(ctx->w.bounce_page, ext4_bounce_page_pool); - } + if (ctx->flags & EXT4_WRITE_PATH_FL && ctx->w.bounce_page) + mempool_free(ctx->w.bounce_page, ext4_bounce_page_pool); ctx->w.bounce_page = NULL; ctx->w.control_page = NULL; if (ctx->flags & EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL) { @@ -317,22 +313,11 @@ static int ext4_page_crypto(struct ext4_crypto_ctx *ctx, static struct page *alloc_bounce_page(struct ext4_crypto_ctx *ctx) { - struct page *ciphertext_page = alloc_page(GFP_NOFS); - - if (!ciphertext_page) { - /* This is a potential bottleneck, but at least we'll have - * forward progress. */ - ciphertext_page = mempool_alloc(ext4_bounce_page_pool, - GFP_NOFS); - if (ciphertext_page == NULL) - return ERR_PTR(-ENOMEM); - ctx->flags &= ~EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL; - } else { - ctx->flags |= EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL; - } + ctx->w.bounce_page = mempool_alloc(ext4_bounce_page_pool, GFP_NOWAIT); + if (ctx->w.bounce_page == NULL) + return ERR_PTR(-ENOMEM); ctx->flags |= EXT4_WRITE_PATH_FL; - ctx->w.bounce_page = ciphertext_page; - return ciphertext_page; + return ctx->w.bounce_page; } /** -- cgit v1.2.3