922cea35f8
- makedumpfile-is_cache_page-helper.patch: Add is_cache_page() helper to check if a page belongs to the cache (bsc#1088354). - makedumpfile-check-PG_swapbacked.patch: Check PG_swapbacked for swap cache pages (bsc#1088354). OBS-URL: https://build.opensuse.org/request/show/602491 OBS-URL: https://build.opensuse.org/package/show/Kernel:kdump/makedumpfile?expand=0&rev=123
124 lines
4.7 KiB
Diff
124 lines
4.7 KiB
Diff
From: Petr Tesarik <ptesarik@suse.com>
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Date: Fri, 13 Apr 2018 17:35:55 +0200
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Subject: Check PG_swapbacked for swap cache pages
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References: bsc#1088354
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Upstream: posted 2018-04-13
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When page cache is filtered out (dump level bitmap includes 2 or 4),
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makedumpfile checks the PG_swapcache bit, but since kernel commit
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6326fec1122cde256bd2a8c63f2606e08e44ce1d (v4.10-rc1~7) this bit is
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an alias for PG_owner_priv_1, which is also used by filesystem
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code (PG_checked) and Xen (PG_pinned and PG_foreign).
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With these kernels, the PG_swapcache flag is valid only if
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PG_swapbacked is set. A Linux kernel patch has already been
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submitted to export the value of PG_swapbacked in VMCOREINFO.
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Since there are released kernels in the wild which do not export the
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value, a fallback is implemented. I considered these three situations:
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1. Kernels before v2.6.28-rc1~244:
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PG_swapbacked does not exist, so it must not be checked.
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Instead, check PG_swapcache, which is never overloaded for
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another purpose.
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2. Kernels between v2.6.28-rc1~244 and v4.10-rc1~7:
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It is sufficient to check only PG_swapcache, but PG_swapbacked
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may also be checked (it is always set if PG_swapcache is set).
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3. Kernels since v4.10-rc1~7:
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PG_swapbacked must be checked.
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If PG_swapbacked value is known (exported or read from debuginfo),
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it is always safe to use it (case 2 or 3). If PG_swapbacked is not
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known, it is safe to ignore it for cases 1 and 2, but not 3.
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Thankfully, the new value of PG_swapcache (since v4.10-rc1~7) is
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less than PG_private (which is known), whereas the old value had
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always been greater than PG_private. Moreover, the flags between
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PG_private and PG_swapbacked haven't changed since v4.10-rc1~7, so
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PG_swapbacked can fall back to PG_private + 6 if unknown.
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Without this patch, all Xen dumps are unusable, because PG_pinned is
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set for all page table pages.
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Signed-off-by: Petr Tesarik <ptesarik@suse.com>
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---
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makedumpfile.c | 19 ++++++++++++++++++-
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makedumpfile.h | 2 ++
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2 files changed, 20 insertions(+), 1 deletion(-)
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--- a/makedumpfile.c
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+++ b/makedumpfile.c
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@@ -252,7 +252,18 @@ isHugetlb(int dtor)
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static int
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is_cache_page(unsigned long flags)
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{
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- return isLRU(flags) || isSwapCache(flags);
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+ if (isLRU(flags))
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+ return TRUE;
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+
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+ /* PG_swapcache is valid only if:
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+ * a. PG_swapbacked bit is set, or
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+ * b. PG_swapbacked did not exist (kernels before 4.10-rc1).
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+ */
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+ if ((NUMBER(PG_swapbacked) == NOT_FOUND_NUMBER || isSwapBacked(flags))
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+ && isSwapCache(flags))
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+ return TRUE;
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+
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+ return FALSE;
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}
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static inline unsigned long
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@@ -1735,6 +1746,7 @@ get_structure_info(void)
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ENUM_NUMBER_INIT(PG_lru, "PG_lru");
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ENUM_NUMBER_INIT(PG_private, "PG_private");
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ENUM_NUMBER_INIT(PG_swapcache, "PG_swapcache");
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+ ENUM_NUMBER_INIT(PG_swapbacked, "PG_swapbacked");
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ENUM_NUMBER_INIT(PG_buddy, "PG_buddy");
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ENUM_NUMBER_INIT(PG_slab, "PG_slab");
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ENUM_NUMBER_INIT(PG_hwpoison, "PG_hwpoison");
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@@ -1988,6 +2000,9 @@ get_value_for_old_linux(void)
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NUMBER(PG_private) = PG_private_ORIGINAL;
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if (NUMBER(PG_swapcache) == NOT_FOUND_NUMBER)
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NUMBER(PG_swapcache) = PG_swapcache_ORIGINAL;
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+ if (NUMBER(PG_swapbacked) == NOT_FOUND_NUMBER
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+ && NUMBER(PG_swapcache) < NUMBER(PG_private))
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+ NUMBER(PG_swapbacked) = NUMBER(PG_private) + 6;
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if (NUMBER(PG_slab) == NOT_FOUND_NUMBER)
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NUMBER(PG_slab) = PG_slab_ORIGINAL;
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if (NUMBER(PG_head_mask) == NOT_FOUND_NUMBER)
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@@ -2264,6 +2279,7 @@ write_vmcoreinfo_data(void)
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WRITE_NUMBER("PG_private", PG_private);
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WRITE_NUMBER("PG_head_mask", PG_head_mask);
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WRITE_NUMBER("PG_swapcache", PG_swapcache);
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+ WRITE_NUMBER("PG_swapbacked", PG_swapbacked);
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WRITE_NUMBER("PG_buddy", PG_buddy);
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WRITE_NUMBER("PG_slab", PG_slab);
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WRITE_NUMBER("PG_hwpoison", PG_hwpoison);
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@@ -2658,6 +2674,7 @@ read_vmcoreinfo(void)
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READ_NUMBER("PG_private", PG_private);
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READ_NUMBER("PG_head_mask", PG_head_mask);
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READ_NUMBER("PG_swapcache", PG_swapcache);
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+ READ_NUMBER("PG_swapbacked", PG_swapbacked);
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READ_NUMBER("PG_slab", PG_slab);
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READ_NUMBER("PG_buddy", PG_buddy);
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READ_NUMBER("PG_hwpoison", PG_hwpoison);
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--- a/makedumpfile.h
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+++ b/makedumpfile.h
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@@ -155,6 +155,7 @@ test_bit(int nr, unsigned long addr)
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#define isPrivate(flags) test_bit(NUMBER(PG_private), flags)
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#define isCompoundHead(flags) (!!((flags) & NUMBER(PG_head_mask)))
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#define isSwapCache(flags) test_bit(NUMBER(PG_swapcache), flags)
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+#define isSwapBacked(flags) test_bit(NUMBER(PG_swapbacked), flags)
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#define isHWPOISON(flags) (test_bit(NUMBER(PG_hwpoison), flags) \
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&& (NUMBER(PG_hwpoison) != NOT_FOUND_NUMBER))
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@@ -1869,6 +1870,7 @@ struct number_table {
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long PG_head;
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long PG_head_mask;
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long PG_swapcache;
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+ long PG_swapbacked;
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long PG_buddy;
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long PG_slab;
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long PG_hwpoison;
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