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Subject[PATCH v2] mm/vmalloc: Replace opencoded 4-level page walkers
Date
Rather than open-code the intricacies of walking the 4-level page
tables, use the generic page table walker apply_to_page_range() instead.

The important change is that it now cleans up after an
unsuccessful insertion and propagates the correct error. The current
failure may lead to a WARN if we encounter ENOMEM in one
vmap_pte_range() and later retry with the same page range:

WARNING: CPU: 0 PID: 605 at mm/vmalloc.c:136 vmap_page_range_noflush+0x2c1/0x340
i.e. WARN_ON(!pte_none(*pte))

v2: Don't convert the vunmap code over to apply_to_page_range() as it
may try to allocate during atomic sections, such as exiting a task:

[ 9.837563] [<ffffffff810519b0>] pte_alloc_one_kernel+0x10/0x20
[ 9.837568] [<ffffffff811a7486>] __pte_alloc_kernel+0x16/0xa0
[ 9.837572] [<ffffffff811aaa76>] apply_to_page_range+0x3f6/0x460
[ 9.837576] [<ffffffff811b8888>] free_unmap_vmap_area_noflush+0x28/0x40
[ 9.837579] [<ffffffff811b9dcd>] remove_vm_area+0x4d/0x60
[ 9.837582] [<ffffffff811b9e09>] __vunmap+0x29/0x130
[ 9.837585] [<ffffffff811b9f7d>] vfree+0x3d/0x90
[ 9.837589] [<ffffffff8107ace6>] put_task_stack+0x76/0x130

and it also upsets sparc64:

[ 2.530785] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff,max_idle_ns: 19112604462750000 ns
[ 2.532359] kernel BUG at mm/memory.c:1881!
[ 2.532798] \|/ ____ \|/
[ 2.532798] "@'/ .. \`@"
[ 2.532798] /_| \__/ |_\
[ 2.532798] \__U_/
[ 2.533250] swapper(1): Kernel bad sw trap 5 [#1]
[ 2.533705] CPU: 0 PID: 1 Comm: swapper Not tainted 4.9.0-rc2+ #1
[ 2.534129] task: fffff8001f0af620 task.stack: fffff8001f0b0000
[ 2.534505] TSTATE: 0000004480001605 TPC: 00000000005124d8 TNPC: 00000000005124dc Y: 00000035 Not tainted
[ 2.535112] TPC: <apply_to_page_range+0x2f8/0x3a0>
[ 2.535469] g0: 00000000009b1548 g1: 0000000000a4a990 g2: 0000000000a4a990 g3: 0000000000b37694
[ 2.535857] g4: fffff8001f0af620 g5: 0000000000000000 g6: fffff8001f0b0000 g7: 0000000000000000
[ 2.536236] o0: 000000000000001f o1: 00000000009ac2c0 o2: 0000000000000759 o3: 0000000000122000
[ 2.536695] o4: 0000000000000000 o5: 00000000009ac2c0 sp: fffff8001f0b2d61 ret_pc: 00000000005124d0
[ 2.537086] RPC: <apply_to_page_range+0x2f0/0x3a0>
[ 2.537454] l0: 0000000000000000 l1: 0000000000002000 l2: fffff8001f10b000 l3: 0000000100002000
[ 2.537843] l4: 0000000000aef910 l5: 0000000000a5e7e8 l6: 0000000100001fff l7: ffffffffff800000
[ 2.538229] i0: 0000000000a5e7e8 i1: 0000000100000000 i2: 0000000100002000 i3: 000000000051e5e0
[ 2.538613] i4: fffff8001f0b3708 i5: fffff8001f10c000 i6: fffff8001f0b2e51 i7: 000000000051e8e0
[ 2.539007] I7: <vmap_page_range_noflush+0x40/0x80>
[ 2.539387] Call Trace:
[ 2.539765] [000000000051e8e0] vmap_page_range_noflush+0x40/0x80
[ 2.540139] [000000000051e970] map_vm_area+0x50/0x80
[ 2.540492] [000000000051f84c] __vmalloc_node_range+0x14c/0x260
[ 2.540848] [000000000051f98c] __vmalloc_node+0x2c/0x40
[ 2.541198] [00000000004d39cc] bpf_prog_alloc+0x2c/0xa0
[ 2.541554] [00000000008129bc] bpf_prog_create+0x3c/0xa0
[ 2.541916] [0000000000adb21c] ptp_classifier_init+0x20/0x4c
[ 2.542271] [0000000000ad9808] sock_init+0x90/0xa0
[ 2.542622] [0000000000426cb0] do_one_initcall+0x30/0x160
[ 2.542978] [0000000000aaeaec] kernel_init_freeable+0x10c/0x1b0
[ 2.543332] [00000000008e3324] kernel_init+0x4/0x100
[ 2.543681] [0000000000405f04] ret_from_fork+0x1c/0x2c

which was a BUG_ON(pmd_huge(*pmd)) and seems to be a general problem
pointed out by the generic pagewalkers that is handled by vunmap.
Perhaps we need a clear_page_range()?

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98269
References: msg-id:20161028171825.GA15116@roeck-us.net
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Wang Xiaoqiang <wangxq10@lzu.edu.cn>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: linux-mm@kvack.org
---
mm/vmalloc.c | 108 ++++++++++++++---------------------------------------------
1 file changed, 26 insertions(+), 82 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 673942094328..fef79affc4ab 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -131,80 +131,27 @@ static void vunmap_page_range(unsigned long addr, unsigned long end)
} while (pgd++, addr = next, addr != end);
}

-static int vmap_pte_range(pmd_t *pmd, unsigned long addr,
- unsigned long end, pgprot_t prot, struct page **pages, int *nr)
-{
- pte_t *pte;
-
- /*
- * nr is a running index into the array which helps higher level
- * callers keep track of where we're up to.
- */
-
- pte = pte_alloc_kernel(pmd, addr);
- if (!pte)
- return -ENOMEM;
- do {
- struct page *page = pages[*nr];
-
- if (WARN_ON(!pte_none(*pte)))
- return -EBUSY;
- if (WARN_ON(!page))
- return -ENOMEM;
- set_pte_at(&init_mm, addr, pte, mk_pte(page, prot));
- (*nr)++;
- } while (pte++, addr += PAGE_SIZE, addr != end);
- return 0;
-}
+struct vmap_page {
+ pgprot_t prot;
+ struct page **pages;
+ unsigned long count;
+};

-static int vmap_pmd_range(pud_t *pud, unsigned long addr,
- unsigned long end, pgprot_t prot, struct page **pages, int *nr)
+static int vmap_page(pte_t *pte, pgtable_t token,
+ unsigned long addr, void *data)
{
- pmd_t *pmd;
- unsigned long next;
-
- pmd = pmd_alloc(&init_mm, pud, addr);
- if (!pmd)
- return -ENOMEM;
- do {
- next = pmd_addr_end(addr, end);
- if (vmap_pte_range(pmd, addr, next, prot, pages, nr))
- return -ENOMEM;
- } while (pmd++, addr = next, addr != end);
- return 0;
-}
+ struct vmap_page *v = data;
+ struct page *page;

-static int vmap_pud_range(p4d_t *p4d, unsigned long addr,
- unsigned long end, pgprot_t prot, struct page **pages, int *nr)
-{
- pud_t *pud;
- unsigned long next;
+ if (WARN_ON(!pte_none(*pte)))
+ return -EBUSY;

- pud = pud_alloc(&init_mm, p4d, addr);
- if (!pud)
+ page = v->pages[v->count];
+ if (WARN_ON(!page))
return -ENOMEM;
- do {
- next = pud_addr_end(addr, end);
- if (vmap_pmd_range(pud, addr, next, prot, pages, nr))
- return -ENOMEM;
- } while (pud++, addr = next, addr != end);
- return 0;
-}

-static int vmap_p4d_range(pgd_t *pgd, unsigned long addr,
- unsigned long end, pgprot_t prot, struct page **pages, int *nr)
-{
- p4d_t *p4d;
- unsigned long next;
-
- p4d = p4d_alloc(&init_mm, pgd, addr);
- if (!p4d)
- return -ENOMEM;
- do {
- next = p4d_addr_end(addr, end);
- if (vmap_pud_range(p4d, addr, next, prot, pages, nr))
- return -ENOMEM;
- } while (p4d++, addr = next, addr != end);
+ set_pte_at(&init_mm, addr, pte, mk_pte(page, v->prot));
+ v->count++;
return 0;
}

@@ -217,22 +164,19 @@ static int vmap_p4d_range(pgd_t *pgd, unsigned long addr,
static int vmap_page_range_noflush(unsigned long start, unsigned long end,
pgprot_t prot, struct page **pages)
{
- pgd_t *pgd;
- unsigned long next;
- unsigned long addr = start;
- int err = 0;
- int nr = 0;
+ struct vmap_page v = { prot, pages };
+ int err;

- BUG_ON(addr >= end);
- pgd = pgd_offset_k(addr);
- do {
- next = pgd_addr_end(addr, end);
- err = vmap_p4d_range(pgd, addr, next, prot, pages, &nr);
- if (err)
- return err;
- } while (pgd++, addr = next, addr != end);
+ if ((end - start) >> PAGE_SHIFT > INT_MAX)
+ return -EINVAL;
+
+ err = apply_to_page_range(&init_mm, start, end - start, vmap_page, &v);
+ if (unlikely(err)) {
+ vunmap_page_range(start, start + (v.count << PAGE_SHIFT));
+ return err;
+ }

- return nr;
+ return v.count;
}

static int vmap_page_range(unsigned long start, unsigned long end,
--
2.15.1
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