Hi Petr, Sorry. I can't take time enough for makedumpfile recently. I would like to reply by May 11th. Please wait some weeks. Thanks Tachibana > -----Original Message----- > From: Petr Tesarik [mailto:ptesarik@xxxxxxx] > Sent: Tuesday, April 24, 2018 7:43 PM > To: Tachibana Masaki() <mas-tachibana@xxxxxxxxxxxxx>; Nakayama Takuya() <tak-nakayama@xxxxxxxxxxxxx>; > kexec-ml <kexec@xxxxxxxxxxxxxxxxxxx> > Subject: Re: [PATCH 2/2] Check PG_swapbacked for swap cache pages > > Hi Masaki-san, > > what is the status of this patch? Do you have any concerns? > > TIA, > Petr T > > On Fri, 13 Apr 2018 18:29:59 +0200 > Petr Tesarik <ptesarik@xxxxxxx> wrote: > > > When page cache is filtered out (dump level bitmap includes 2 or 4), > > makedumpfile checks the PG_swapcache bit, but since kernel commit > > 6326fec1122cde256bd2a8c63f2606e08e44ce1d (v4.10-rc1~7) this bit is > > an alias for PG_owner_priv_1, which is also used by filesystem > > code (PG_checked) and Xen (PG_pinned and PG_foreign). > > > > With these kernels, the PG_swapcache flag is valid only if > > PG_swapbacked is set. A Linux kernel patch has already been > > submitted to export the value of PG_swapbacked in VMCOREINFO. > > > > Since there are released kernels in the wild which do not export the > > value, a fallback is implemented. I considered these three situations: > > > > 1. Kernels before v2.6.28-rc1~244: > > PG_swapbacked does not exist, so it must not be checked. > > Instead, check PG_swapcache, which is never overloaded for > > another purpose. > > > > 2. Kernels between v2.6.28-rc1~244 and v4.10-rc1~7: > > It is sufficient to check only PG_swapcache, but PG_swapbacked > > may also be checked (it is always set if PG_swapcache is set). > > > > 3. Kernels since v4.10-rc1~7: > > PG_swapbacked must be checked. > > > > If PG_swapbacked value is known (exported or read from debuginfo), > > it is always safe to use it (case 2 or 3). If PG_swapbacked is not > > known, it is safe to ignore it for cases 1 and 2, but not 3. > > Thankfully, the new value of PG_swapcache (since v4.10-rc1~7) is > > less than PG_private (which is known), whereas the old value had > > always been greater than PG_private. Moreover, the flags between > > PG_private and PG_swapbacked haven't changed since v4.10-rc1~7, so > > PG_swapbacked can fall back to PG_private + 6 if unknown. > > > > Without this patch, all Xen dumps are unusable, because PG_pinned is > > set for all page table pages. > > > > Signed-off-by: Petr Tesarik <ptesarik@xxxxxxxx> > > --- > > makedumpfile.c | 19 ++++++++++++++++++- > > makedumpfile.h | 2 ++ > > 2 files changed, 20 insertions(+), 1 deletion(-) > > > > diff --git a/makedumpfile.c b/makedumpfile.c > > index 175ba68..ec04a88 100644 > > --- a/makedumpfile.c > > +++ b/makedumpfile.c > > @@ -252,7 +252,18 @@ isHugetlb(unsigned long dtor) > > static int > > is_cache_page(unsigned long flags) > > { > > - return isLRU(flags) || isSwapCache(flags); > > + if (isLRU(flags)) > > + return TRUE; > > + > > + /* PG_swapcache is valid only if: > > + * a. PG_swapbacked bit is set, or > > + * b. PG_swapbacked did not exist (kernels before 4.10-rc1). > > + */ > > + if ((NUMBER(PG_swapbacked) == NOT_FOUND_NUMBER || isSwapBacked(flags)) > > + && isSwapCache(flags)) > > + return TRUE; > > + > > + return FALSE; > > } > > > > static inline unsigned long > > @@ -1735,6 +1746,7 @@ get_structure_info(void) > > ENUM_NUMBER_INIT(PG_lru, "PG_lru"); > > ENUM_NUMBER_INIT(PG_private, "PG_private"); > > ENUM_NUMBER_INIT(PG_swapcache, "PG_swapcache"); > > + ENUM_NUMBER_INIT(PG_swapbacked, "PG_swapbacked"); > > ENUM_NUMBER_INIT(PG_buddy, "PG_buddy"); > > ENUM_NUMBER_INIT(PG_slab, "PG_slab"); > > ENUM_NUMBER_INIT(PG_hwpoison, "PG_hwpoison"); > > @@ -1988,6 +2000,9 @@ get_value_for_old_linux(void) > > NUMBER(PG_private) = PG_private_ORIGINAL; > > if (NUMBER(PG_swapcache) == NOT_FOUND_NUMBER) > > NUMBER(PG_swapcache) = PG_swapcache_ORIGINAL; > > + if (NUMBER(PG_swapbacked) == NOT_FOUND_NUMBER > > + && NUMBER(PG_swapcache) < NUMBER(PG_private)) > > + NUMBER(PG_swapbacked) = NUMBER(PG_private) + 6; > > if (NUMBER(PG_slab) == NOT_FOUND_NUMBER) > > NUMBER(PG_slab) = PG_slab_ORIGINAL; > > if (NUMBER(PG_head_mask) == NOT_FOUND_NUMBER) > > @@ -2264,6 +2279,7 @@ write_vmcoreinfo_data(void) > > WRITE_NUMBER("PG_private", PG_private); > > WRITE_NUMBER("PG_head_mask", PG_head_mask); > > WRITE_NUMBER("PG_swapcache", PG_swapcache); > > + WRITE_NUMBER("PG_swapbacked", PG_swapbacked); > > WRITE_NUMBER("PG_buddy", PG_buddy); > > WRITE_NUMBER("PG_slab", PG_slab); > > WRITE_NUMBER("PG_hwpoison", PG_hwpoison); > > @@ -2658,6 +2674,7 @@ read_vmcoreinfo(void) > > READ_NUMBER("PG_private", PG_private); > > READ_NUMBER("PG_head_mask", PG_head_mask); > > READ_NUMBER("PG_swapcache", PG_swapcache); > > + READ_NUMBER("PG_swapbacked", PG_swapbacked); > > READ_NUMBER("PG_slab", PG_slab); > > READ_NUMBER("PG_buddy", PG_buddy); > > READ_NUMBER("PG_hwpoison", PG_hwpoison); > > diff --git a/makedumpfile.h b/makedumpfile.h > > index 6205ef3..fe306bb 100644 > > --- a/makedumpfile.h > > +++ b/makedumpfile.h > > @@ -155,6 +155,7 @@ test_bit(int nr, unsigned long addr) > > #define isPrivate(flags) test_bit(NUMBER(PG_private), flags) > > #define isCompoundHead(flags) (!!((flags) & NUMBER(PG_head_mask))) > > #define isSwapCache(flags) test_bit(NUMBER(PG_swapcache), flags) > > +#define isSwapBacked(flags) test_bit(NUMBER(PG_swapbacked), flags) > > #define isHWPOISON(flags) (test_bit(NUMBER(PG_hwpoison), flags) \ > > && (NUMBER(PG_hwpoison) != NOT_FOUND_NUMBER)) > > > > @@ -1881,6 +1882,7 @@ struct number_table { > > long PG_head; > > long PG_head_mask; > > long PG_swapcache; > > + long PG_swapbacked; > > long PG_buddy; > > long PG_slab; > > long PG_hwpoison; > _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
