--- /dev/null
+From e91d8d78237de8d7120c320b3645b7100848f24d Mon Sep 17 00:00:00 2001
+From: Minchan Kim <minchan@kernel.org>
+Date: Sat, 5 Dec 2020 22:14:51 -0800
+Subject: mm/zsmalloc.c: drop ZSMALLOC_PGTABLE_MAPPING
+
+From: Minchan Kim <minchan@kernel.org>
+
+commit e91d8d78237de8d7120c320b3645b7100848f24d upstream.
+
+While I was doing zram testing, I found sometimes decompression failed
+since the compression buffer was corrupted. With investigation, I found
+below commit calls cond_resched unconditionally so it could make a
+problem in atomic context if the task is reschedule.
+
+ BUG: sleeping function called from invalid context at mm/vmalloc.c:108
+ in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 946, name: memhog
+ 3 locks held by memhog/946:
+ #0: ffff9d01d4b193e8 (&mm->mmap_lock#2){++++}-{4:4}, at: __mm_populate+0x103/0x160
+ #1: ffffffffa3d53de0 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath.constprop.0+0xa98/0x1160
+ #2: ffff9d01d56b8110 (&zspage->lock){.+.+}-{3:3}, at: zs_map_object+0x8e/0x1f0
+ CPU: 0 PID: 946 Comm: memhog Not tainted 5.9.3-00011-gc5bfc0287345-dirty #316
+ Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014
+ Call Trace:
+ unmap_kernel_range_noflush+0x2eb/0x350
+ unmap_kernel_range+0x14/0x30
+ zs_unmap_object+0xd5/0xe0
+ zram_bvec_rw.isra.0+0x38c/0x8e0
+ zram_rw_page+0x90/0x101
+ bdev_write_page+0x92/0xe0
+ __swap_writepage+0x94/0x4a0
+ pageout+0xe3/0x3a0
+ shrink_page_list+0xb94/0xd60
+ shrink_inactive_list+0x158/0x460
+
+We can fix this by removing the ZSMALLOC_PGTABLE_MAPPING feature (which
+contains the offending calling code) from zsmalloc.
+
+Even though this option showed some amount improvement(e.g., 30%) in
+some arm32 platforms, it has been headache to maintain since it have
+abused APIs[1](e.g., unmap_kernel_range in atomic context).
+
+Since we are approaching to deprecate 32bit machines and already made
+the config option available for only builtin build since v5.8, lastly it
+has been not default option in zsmalloc, it's time to drop the option
+for better maintenance.
+
+[1] http://lore.kernel.org/linux-mm/20201105170249.387069-1-minchan@kernel.org
+
+Fixes: e47110e90584 ("mm/vunmap: add cond_resched() in vunmap_pmd_range")
+Signed-off-by: Minchan Kim <minchan@kernel.org>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+Cc: Tony Lindgren <tony@atomide.com>
+Cc: Christoph Hellwig <hch@infradead.org>
+Cc: Harish Sriram <harish@linux.ibm.com>
+Cc: Uladzislau Rezki <urezki@gmail.com>
+Cc: <stable@vger.kernel.org>
+Link: https://lkml.kernel.org/r/20201117202916.GA3856507@google.com
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+
+---
+ include/linux/zsmalloc.h | 1 -
+ mm/Kconfig | 13 -------------
+ mm/zsmalloc.c | 46 ----------------------------------------------
+ 3 files changed, 60 deletions(-)
+
+--- a/include/linux/zsmalloc.h
++++ b/include/linux/zsmalloc.h
+@@ -20,7 +20,6 @@
+ * zsmalloc mapping modes
+ *
+ * NOTE: These only make a difference when a mapped object spans pages.
+- * They also have no effect when PGTABLE_MAPPING is selected.
+ */
+ enum zs_mapmode {
+ ZS_MM_RW, /* normal read-write mapping */
+--- a/mm/Kconfig
++++ b/mm/Kconfig
+@@ -576,19 +576,6 @@ config ZSMALLOC
+ returned by an alloc(). This handle must be mapped in order to
+ access the allocated space.
+
+-config PGTABLE_MAPPING
+- bool "Use page table mapping to access object in zsmalloc"
+- depends on ZSMALLOC
+- help
+- By default, zsmalloc uses a copy-based object mapping method to
+- access allocations that span two pages. However, if a particular
+- architecture (ex, ARM) performs VM mapping faster than copying,
+- then you should select this. This causes zsmalloc to use page table
+- mapping rather than copying for object mapping.
+-
+- You can check speed with zsmalloc benchmark:
+- https://github.com/spartacus06/zsmapbench
+-
+ config ZSMALLOC_STAT
+ bool "Export zsmalloc statistics"
+ depends on ZSMALLOC
+--- a/mm/zsmalloc.c
++++ b/mm/zsmalloc.c
+@@ -293,11 +293,7 @@ struct zspage {
+ };
+
+ struct mapping_area {
+-#ifdef CONFIG_PGTABLE_MAPPING
+- struct vm_struct *vm; /* vm area for mapping object that span pages */
+-#else
+ char *vm_buf; /* copy buffer for objects that span pages */
+-#endif
+ char *vm_addr; /* address of kmap_atomic()'ed pages */
+ enum zs_mapmode vm_mm; /* mapping mode */
+ };
+@@ -1113,46 +1109,6 @@ static struct zspage *find_get_zspage(st
+ return zspage;
+ }
+
+-#ifdef CONFIG_PGTABLE_MAPPING
+-static inline int __zs_cpu_up(struct mapping_area *area)
+-{
+- /*
+- * Make sure we don't leak memory if a cpu UP notification
+- * and zs_init() race and both call zs_cpu_up() on the same cpu
+- */
+- if (area->vm)
+- return 0;
+- area->vm = alloc_vm_area(PAGE_SIZE * 2, NULL);
+- if (!area->vm)
+- return -ENOMEM;
+- return 0;
+-}
+-
+-static inline void __zs_cpu_down(struct mapping_area *area)
+-{
+- if (area->vm)
+- free_vm_area(area->vm);
+- area->vm = NULL;
+-}
+-
+-static inline void *__zs_map_object(struct mapping_area *area,
+- struct page *pages[2], int off, int size)
+-{
+- BUG_ON(map_vm_area(area->vm, PAGE_KERNEL, pages));
+- area->vm_addr = area->vm->addr;
+- return area->vm_addr + off;
+-}
+-
+-static inline void __zs_unmap_object(struct mapping_area *area,
+- struct page *pages[2], int off, int size)
+-{
+- unsigned long addr = (unsigned long)area->vm_addr;
+-
+- unmap_kernel_range(addr, PAGE_SIZE * 2);
+-}
+-
+-#else /* CONFIG_PGTABLE_MAPPING */
+-
+ static inline int __zs_cpu_up(struct mapping_area *area)
+ {
+ /*
+@@ -1233,8 +1189,6 @@ out:
+ pagefault_enable();
+ }
+
+-#endif /* CONFIG_PGTABLE_MAPPING */
+-
+ static int zs_cpu_prepare(unsigned int cpu)
+ {
+ struct mapping_area *area;
projects / thirdparty / kernel / stable-queue.git / commitdiff
