From a1de4d7fad370939668683e7fa52c2022dbaf408 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Mon, 17 Sep 2018 23:14:13 +0200 Subject: [PATCH] 3.18-stable patches added patches: mm-get-rid-of-vmacache_flush_all-entirely.patch --- ...t-rid-of-vmacache_flush_all-entirely.patch | 147 ++++++++++++++++++ queue-3.18/series | 1 + 2 files changed, 148 insertions(+) create mode 100644 queue-3.18/mm-get-rid-of-vmacache_flush_all-entirely.patch diff --git a/queue-3.18/mm-get-rid-of-vmacache_flush_all-entirely.patch b/queue-3.18/mm-get-rid-of-vmacache_flush_all-entirely.patch new file mode 100644 index 00000000000..39a0e0f38b3 --- /dev/null +++ b/queue-3.18/mm-get-rid-of-vmacache_flush_all-entirely.patch @@ -0,0 +1,147 @@ +From 7a9cdebdcc17e426fb5287e4a82db1dfe86339b2 Mon Sep 17 00:00:00 2001 +From: Linus Torvalds +Date: Wed, 12 Sep 2018 23:57:48 -1000 +Subject: mm: get rid of vmacache_flush_all() entirely + +From: Linus Torvalds + +commit 7a9cdebdcc17e426fb5287e4a82db1dfe86339b2 upstream. + +Jann Horn points out that the vmacache_flush_all() function is not only +potentially expensive, it's buggy too. It also happens to be entirely +unnecessary, because the sequence number overflow case can be avoided by +simply making the sequence number be 64-bit. That doesn't even grow the +data structures in question, because the other adjacent fields are +already 64-bit. + +So simplify the whole thing by just making the sequence number overflow +case go away entirely, which gets rid of all the complications and makes +the code faster too. Win-win. + +[ Oleg Nesterov points out that the VMACACHE_FULL_FLUSHES statistics + also just goes away entirely with this ] + +Reported-by: Jann Horn +Suggested-by: Will Deacon +Acked-by: Davidlohr Bueso +Cc: Oleg Nesterov +Cc: stable@kernel.org +Signed-off-by: Linus Torvalds +Signed-off-by: Greg Kroah-Hartman + +--- + include/linux/mm_types.h | 2 +- + include/linux/sched.h | 2 +- + include/linux/vmacache.h | 5 ----- + mm/debug.c | 4 ++-- + mm/vmacache.c | 36 ------------------------------------ + 5 files changed, 4 insertions(+), 45 deletions(-) + +--- a/include/linux/mm_types.h ++++ b/include/linux/mm_types.h +@@ -345,7 +345,7 @@ struct kioctx_table; + struct mm_struct { + struct vm_area_struct *mmap; /* list of VMAs */ + struct rb_root mm_rb; +- u32 vmacache_seqnum; /* per-thread vmacache */ ++ u64 vmacache_seqnum; /* per-thread vmacache */ + #ifdef CONFIG_MMU + unsigned long (*get_unmapped_area) (struct file *filp, + unsigned long addr, unsigned long len, +--- a/include/linux/sched.h ++++ b/include/linux/sched.h +@@ -1315,7 +1315,7 @@ struct task_struct { + unsigned brk_randomized:1; + #endif + /* per-thread vma caching */ +- u32 vmacache_seqnum; ++ u64 vmacache_seqnum; + struct vm_area_struct *vmacache[VMACACHE_SIZE]; + #if defined(SPLIT_RSS_COUNTING) + struct task_rss_stat rss_stat; +--- a/include/linux/vmacache.h ++++ b/include/linux/vmacache.h +@@ -15,7 +15,6 @@ static inline void vmacache_flush(struct + memset(tsk->vmacache, 0, sizeof(tsk->vmacache)); + } + +-extern void vmacache_flush_all(struct mm_struct *mm); + extern void vmacache_update(unsigned long addr, struct vm_area_struct *newvma); + extern struct vm_area_struct *vmacache_find(struct mm_struct *mm, + unsigned long addr); +@@ -29,10 +28,6 @@ extern struct vm_area_struct *vmacache_f + static inline void vmacache_invalidate(struct mm_struct *mm) + { + mm->vmacache_seqnum++; +- +- /* deal with overflows */ +- if (unlikely(mm->vmacache_seqnum == 0)) +- vmacache_flush_all(mm); + } + + #endif /* __LINUX_VMACACHE_H */ +--- a/mm/debug.c ++++ b/mm/debug.c +@@ -166,7 +166,7 @@ EXPORT_SYMBOL(dump_vma); + + void dump_mm(const struct mm_struct *mm) + { +- pr_emerg("mm %p mmap %p seqnum %d task_size %lu\n" ++ pr_emerg("mm %p mmap %p seqnum %llu task_size %lu\n" + #ifdef CONFIG_MMU + "get_unmapped_area %p\n" + #endif +@@ -196,7 +196,7 @@ void dump_mm(const struct mm_struct *mm) + #endif + "%s", /* This is here to hold the comma */ + +- mm, mm->mmap, mm->vmacache_seqnum, mm->task_size, ++ mm, mm->mmap, (long long) mm->vmacache_seqnum, mm->task_size, + #ifdef CONFIG_MMU + mm->get_unmapped_area, + #endif +--- a/mm/vmacache.c ++++ b/mm/vmacache.c +@@ -6,42 +6,6 @@ + #include + + /* +- * Flush vma caches for threads that share a given mm. +- * +- * The operation is safe because the caller holds the mmap_sem +- * exclusively and other threads accessing the vma cache will +- * have mmap_sem held at least for read, so no extra locking +- * is required to maintain the vma cache. +- */ +-void vmacache_flush_all(struct mm_struct *mm) +-{ +- struct task_struct *g, *p; +- +- /* +- * Single threaded tasks need not iterate the entire +- * list of process. We can avoid the flushing as well +- * since the mm's seqnum was increased and don't have +- * to worry about other threads' seqnum. Current's +- * flush will occur upon the next lookup. +- */ +- if (atomic_read(&mm->mm_users) == 1) +- return; +- +- rcu_read_lock(); +- for_each_process_thread(g, p) { +- /* +- * Only flush the vmacache pointers as the +- * mm seqnum is already set and curr's will +- * be set upon invalidation when the next +- * lookup is done. +- */ +- if (mm == p->mm) +- vmacache_flush(p); +- } +- rcu_read_unlock(); +-} +- +-/* + * This task may be accessing a foreign mm via (for example) + * get_user_pages()->find_vma(). The vmacache is task-local and this + * task's vmacache pertains to a different mm (ie, its own). There is diff --git a/queue-3.18/series b/queue-3.18/series index 5c854496912..6a8691d2ea2 100644 --- a/queue-3.18/series +++ b/queue-3.18/series @@ -58,3 +58,4 @@ f2fs-fix-to-do-sanity-check-with-sit-nat-_ver_bitmap_bytesize.patch mips-warn_on-invalid-dma-cache-maintenance-not-bug_on.patch xhci-fix-use-after-free-in-xhci_free_virt_device.patch netfilter-x_tables-avoid-stack-out-of-bounds-read-in-xt_copy_counters_from_user.patch +mm-get-rid-of-vmacache_flush_all-entirely.patch -- 2.47.2