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authorTheodore Ts'o <tytso@mit.edu>2015-06-03 09:32:39 -0400
committerTheodore Ts'o <tytso@mit.edu>2015-06-03 09:32:39 -0400
commit3dbb5eb9a3aa04f40e551338eee5e8d06f352fe8 (patch)
treec84bc425081af46b5692e437aa258adb0fe60846
parente298e73bd766768707a7af440691ce2f418f5acc (diff)
downloadop-kernel-dev-3dbb5eb9a3aa04f40e551338eee5e8d06f352fe8.zip
op-kernel-dev-3dbb5eb9a3aa04f40e551338eee5e8d06f352fe8.tar.gz
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 <tytso@mit.edu>
-rw-r--r--fs/ext4/crypto.c27
-rw-r--r--fs/ext4/ext4_crypto.h3
2 files changed, 7 insertions, 23 deletions
diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
index efcb7c0..f5c82e8 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;
}
/**
diff --git a/fs/ext4/ext4_crypto.h b/fs/ext4/ext4_crypto.h
index 34e0d24..ac7d4e8 100644
--- a/fs/ext4/ext4_crypto.h
+++ b/fs/ext4/ext4_crypto.h
@@ -83,8 +83,7 @@ struct ext4_crypt_info {
};
#define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL 0x00000001
-#define EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL 0x00000002
-#define EXT4_WRITE_PATH_FL 0x00000004
+#define EXT4_WRITE_PATH_FL 0x00000002
struct ext4_crypto_ctx {
union {
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