[PATCH v4 04/10] mm, fsdax: Refactor memory-failure handler for dax mapping

Shiyang Ruan
2021-06-04T01:19:08Z

The current memory_failure_dev_pagemap() can only handle single-mapped
dax page for fsdax mode. The dax page could be mapped by multiple files
and offsets if we let reflink feature & fsdax mode work together. So,
we refactor current implementation to support handle memory failure on
each file and offset.

Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
---
fs/dax.c | 21 ++++++++
include/linux/dax.h | 1 +
include/linux/mm.h | 9 ++++
mm/memory-failure.c | 114 ++++++++++++++++++++++++++++----------------
4 files changed, 105 insertions(+), 40 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 62352cbcf0f4..58faca85455a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -389,6 +389,27 @@ static struct page *dax_busy_page(void *entry)
return NULL;
}

+/*
+ * dax_load_pfn - Load pfn of the DAX entry corresponding to a page
+ * @mapping: The file whose entry we want to load
+ * @index: The offset where the DAX entry located in
+ *
+ * Return: pfn of the DAX entry
+ */
+unsigned long dax_load_pfn(struct address_space *mapping, unsigned long index)
+{
+ XA_STATE(xas, &mapping->i_pages, index);
+ void *entry;
+ unsigned long pfn;
+
+ xas_lock_irq(&xas);
+ entry = xas_load(&xas);
+ pfn = dax_to_pfn(entry);
+ xas_unlock_irq(&xas);
+
+ return pfn;
+}
+
/*
* dax_lock_mapping_entry - Lock the DAX entry corresponding to a page
* @page: The page whose entry we want to lock
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 1ce343a960ab..6e758daa5004 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -158,6 +158,7 @@ int dax_writeback_mapping_range(struct address_space *mapping,

struct page *dax_layout_busy_page(struct address_space *mapping);
struct page *dax_layout_busy_page_range(struct address_space *mapping, loff_t start, loff_t end);
+unsigned long dax_load_pfn(struct address_space *mapping, unsigned long index);
dax_entry_t dax_lock_page(struct page *page);
void dax_unlock_page(struct page *page, dax_entry_t cookie);
#else
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c274f75efcf9..2b7527e93c77 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1187,6 +1187,14 @@ static inline bool is_device_private_page(const struct page *page)
page->pgmap->type == MEMORY_DEVICE_PRIVATE;
}

+static inline bool is_device_fsdax_page(const struct page *page)
+{
+ return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
+ IS_ENABLED(CONFIG_FS_DAX) &&
+ is_zone_device_page(page) &&
+ page->pgmap->type == MEMORY_DEVICE_FS_DAX;
+}
+
static inline bool is_pci_p2pdma_page(const struct page *page)
{
return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
@@ -3078,6 +3086,7 @@ enum mf_flags {
MF_MUST_KILL = 1 << 2,
MF_SOFT_OFFLINE = 1 << 3,
};
+int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index, int flags);
extern int memory_failure(unsigned long pfn, int flags);
extern void memory_failure_queue(unsigned long pfn, int flags);
extern void memory_failure_queue_kick(int cpu);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 85ad98c00fd9..4377e727d478 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -56,6 +56,7 @@
#include <linux/kfifo.h>
#include <linux/ratelimit.h>
#include <linux/page-isolation.h>
+#include <linux/dax.h>
#include "internal.h"
#include "ras/ras_event.h"

@@ -120,6 +121,13 @@ static int hwpoison_filter_dev(struct page *p)
if (PageSlab(p))
return -EINVAL;

+ if (pfn_valid(page_to_pfn(p))) {
+ if (is_device_fsdax_page(p))
+ return 0;
+ else
+ return -EINVAL;
+ }
+
mapping = page_mapping(p);
if (mapping == NULL || mapping->host == NULL)
return -EINVAL;
@@ -290,10 +298,9 @@ void shake_page(struct page *p, int access)
}
EXPORT_SYMBOL_GPL(shake_page);

-static unsigned long dev_pagemap_mapping_shift(struct page *page,
- struct vm_area_struct *vma)
+static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
+ unsigned long address)
{
- unsigned long address = vma_address(page, vma);
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
@@ -333,9 +340,8 @@ static unsigned long dev_pagemap_mapping_shift(struct page *page,
* Schedule a process for later kill.
* Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
*/
-static void add_to_kill(struct task_struct *tsk, struct page *p,
- struct vm_area_struct *vma,
- struct list_head *to_kill)
+static void add_to_kill(struct task_struct *tsk, struct page *p, pgoff_t pgoff,
+ struct vm_area_struct *vma, struct list_head *to_kill)
{
struct to_kill *tk;

@@ -346,9 +352,12 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
}

tk->addr = page_address_in_vma(p, vma);
- if (is_zone_device_page(p))
- tk->size_shift = dev_pagemap_mapping_shift(p, vma);
- else
+ if (is_zone_device_page(p)) {
+ if (is_device_fsdax_page(p))
+ tk->addr = vma->vm_start +
+ ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+ tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
+ } else
tk->size_shift = page_shift(compound_head(p));

/*
@@ -496,7 +505,7 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
if (!page_mapped_in_vma(page, vma))
continue;
if (vma->vm_mm == t->mm)
- add_to_kill(t, page, vma, to_kill);
+ add_to_kill(t, page, 0, vma, to_kill);
}
}
read_unlock(&tasklist_lock);
@@ -506,24 +515,19 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
/*
* Collect processes when the error hit a file mapped page.
*/
-static void collect_procs_file(struct page *page, struct list_head *to_kill,
- int force_early)
+static void collect_procs_file(struct page *page, struct address_space *mapping,
+ pgoff_t pgoff, struct list_head *to_kill, int force_early)
{
struct vm_area_struct *vma;
struct task_struct *tsk;
- struct address_space *mapping = page->mapping;
- pgoff_t pgoff;

i_mmap_lock_read(mapping);
read_lock(&tasklist_lock);
- pgoff = page_to_pgoff(page);
for_each_process(tsk) {
struct task_struct *t = task_early_kill(tsk, force_early);
-
if (!t)
continue;
- vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
- pgoff) {
+ vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
/*
* Send early kill signal to tasks where a vma covers
* the page but the corrupted page is not necessarily
@@ -532,7 +536,7 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill,
* to be informed of all such data corruptions.
*/
if (vma->vm_mm == t->mm)
- add_to_kill(t, page, vma, to_kill);
+ add_to_kill(t, page, pgoff, vma, to_kill);
}
}
read_unlock(&tasklist_lock);
@@ -551,7 +555,8 @@ static void collect_procs(struct page *page, struct list_head *tokill,
if (PageAnon(page))
collect_procs_anon(page, tokill, force_early);
else
- collect_procs_file(page, tokill, force_early);
+ collect_procs_file(page, page_mapping(page), page_to_pgoff(page),
+ tokill, force_early);
}

static const char *action_name[] = {
@@ -1218,6 +1223,51 @@ static int try_to_split_thp_page(struct page *page, const char *msg)
return 0;
}

+static void unmap_and_kill(struct list_head *to_kill, unsigned long pfn,
+ struct address_space *mapping, pgoff_t index, int flags)
+{
+ struct to_kill *tk;
+ unsigned long size = 0;
+ loff_t start;
+
+ list_for_each_entry(tk, to_kill, nd)
+ if (tk->size_shift)
+ size = max(size, 1UL << tk->size_shift);
+ if (size) {
+ /*
+ * Unmap the largest mapping to avoid breaking up
+ * device-dax mappings which are constant size. The
+ * actual size of the mapping being torn down is
+ * communicated in siginfo, see kill_proc()
+ */
+ start = (index << PAGE_SHIFT) & ~(size - 1);
+ unmap_mapping_range(mapping, start, size, 0);
+ }
+
+ kill_procs(to_kill, flags & MF_MUST_KILL, false, pfn, flags);
+}
+
+int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index, int flags)
+{
+ LIST_HEAD(to_kill);
+ /* load the pfn of the dax mapping file */
+ unsigned long pfn = dax_load_pfn(mapping, index);
+
+ /*
+ * Unlike System-RAM there is no possibility to swap in a
+ * different physical page at a given virtual address, so all
+ * userspace consumption of ZONE_DEVICE memory necessitates
+ * SIGBUS (i.e. MF_MUST_KILL)
+ */
+ flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
+ collect_procs_file(pfn_to_page(pfn), mapping, index, &to_kill,
+ flags & MF_ACTION_REQUIRED);
+
+ unmap_and_kill(&to_kill, pfn, mapping, index, flags);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(mf_dax_kill_procs);
+
static int memory_failure_hugetlb(unsigned long pfn, int flags)
{
struct page *p = pfn_to_page(pfn);
@@ -1298,12 +1348,8 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
struct dev_pagemap *pgmap)
{
struct page *page = pfn_to_page(pfn);
- const bool unmap_success = true;
- unsigned long size = 0;
- struct to_kill *tk;
- LIST_HEAD(tokill);
+ LIST_HEAD(to_kill);
int rc = -EBUSY;
- loff_t start;
dax_entry_t cookie;

if (flags & MF_COUNT_INCREASED)
@@ -1355,22 +1401,10 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
* SIGBUS (i.e. MF_MUST_KILL)
*/
flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
- collect_procs(page, &tokill, flags & MF_ACTION_REQUIRED);
+ collect_procs_file(page, page->mapping, page->index, &to_kill,
+ flags & MF_ACTION_REQUIRED);

- list_for_each_entry(tk, &tokill, nd)
- if (tk->size_shift)
- size = max(size, 1UL << tk->size_shift);
- if (size) {
- /*
- * Unmap the largest mapping to avoid breaking up
- * device-dax mappings which are constant size. The
- * actual size of the mapping being torn down is
- * communicated in siginfo, see kill_proc()
- */
- start = (page->index << PAGE_SHIFT) & ~(size - 1);
- unmap_mapping_range(page->mapping, start, size, 0);
- }
- kill_procs(&tokill, flags & MF_MUST_KILL, !unmap_success, pfn, flags);
+ unmap_and_kill(&to_kill, pfn, page->mapping, page->index, flags);
rc = 0;
unlock:
dax_unlock_page(page, cookie);
--
2.31.1