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Koen Kooi
bb34e69f3d
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net> Signed-off-by: Denys Dmytriyenko <denys@ti.com>
66 lines
2.4 KiB
Diff
66 lines
2.4 KiB
Diff
From 27573d35b38cf9f8b2bb9f1f258bcac632ef4e0e Mon Sep 17 00:00:00 2001
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From: Mikulas Patocka <mpatocka@redhat.com>
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Date: Wed, 28 Mar 2012 18:41:22 +0100
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Subject: [PATCH 118/147] dm crypt: fix mempool deadlock
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commit aeb2deae2660a1773c83d3c6e9e6575daa3855d6 upstream.
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This patch fixes a possible deadlock in dm-crypt's mempool use.
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Currently, dm-crypt reserves a mempool of MIN_BIO_PAGES reserved pages.
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It allocates first MIN_BIO_PAGES with non-failing allocation (the allocation
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cannot fail and waits until the mempool is refilled). Further pages are
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allocated with different gfp flags that allow failing.
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Because allocations may be done in parallel, this code can deadlock. Example:
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There are two processes, each tries to allocate MIN_BIO_PAGES and the processes
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run simultaneously.
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It may end up in a situation where each process allocates (MIN_BIO_PAGES / 2)
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pages. The mempool is exhausted. Each process waits for more pages to be freed
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to the mempool, which never happens.
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To avoid this deadlock scenario, this patch changes the code so that only
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the first page is allocated with non-failing gfp mask. Allocation of further
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pages may fail.
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Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
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Signed-off-by: Milan Broz <mbroz@redhat.com>
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Signed-off-by: Alasdair G Kergon <agk@redhat.com>
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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---
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drivers/md/dm-crypt.c | 10 ++++------
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1 file changed, 4 insertions(+), 6 deletions(-)
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diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
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index 8c2a000..c75d947 100644
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--- a/drivers/md/dm-crypt.c
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+++ b/drivers/md/dm-crypt.c
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@@ -176,7 +176,6 @@ struct crypt_config {
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#define MIN_IOS 16
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#define MIN_POOL_PAGES 32
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-#define MIN_BIO_PAGES 8
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static struct kmem_cache *_crypt_io_pool;
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@@ -848,12 +847,11 @@ static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned size,
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}
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/*
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- * if additional pages cannot be allocated without waiting,
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- * return a partially allocated bio, the caller will then try
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- * to allocate additional bios while submitting this partial bio
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+ * If additional pages cannot be allocated without waiting,
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+ * return a partially-allocated bio. The caller will then try
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+ * to allocate more bios while submitting this partial bio.
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*/
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- if (i == (MIN_BIO_PAGES - 1))
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- gfp_mask = (gfp_mask | __GFP_NOWARN) & ~__GFP_WAIT;
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+ gfp_mask = (gfp_mask | __GFP_NOWARN) & ~__GFP_WAIT;
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len = (size > PAGE_SIZE) ? PAGE_SIZE : size;
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--
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1.7.9.4
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