From 0e023e2ceffdd17a84e9c8dbe30eea69fca8849f Mon Sep 17 00:00:00 2001
From: Yang Shi <shy828301@gmail.com>
Date: Fri, 14 Jan 2022 14:05:19 -0800
Subject: [PATCH] mm: shmem: don't truncate page if memory failure happens v2
References: bsc#1190208 (MM functional and performance backports)
Patch-mainline: v5.17
Git-commit: a7605426666196c5a460dd3de6f8dac1d3c21f00
The current behavior of memory failure is to truncate the page cache
regardless of dirty or clean. If the page is dirty the later access
will get the obsolete data from disk without any notification to the
users. This may cause silent data loss. It is even worse for shmem
since shmem is in-memory filesystem, truncating page cache means
discarding data blocks. The later read would return all zero.
The right approach is to keep the corrupted page in page cache, any
later access would return error for syscalls or SIGBUS for page fault,
until the file is truncated, hole punched or removed. The regular
storage backed filesystems would be more complicated so this patch is
focused on shmem. This also unblock the support for soft offlining
shmem THP.
[akpm@linux-foundation.org: coding style fixes]
[arnd@arndb.de: fix uninitialized variable use in me_pagecache_clean()]
Link: https://lkml.kernel.org/r/20211022064748.4173718-1-arnd@kernel.org
[Fix invalid pointer dereference in shmem_read_mapping_page_gfp() with a
slight different implementation from what Ajay Garg <ajaygargnsit@gmail.com>
and Muchun Song <songmuchun@bytedance.com> proposed and reworked the
error handling of shmem_write_begin() suggested by Linus]
Link: https://lore.kernel.org/linux-mm/20211111084617.6746-1-ajaygargnsit@gmail.com/
Link: https://lkml.kernel.org/r/20211020210755.23964-6-shy828301@gmail.com
Link: https://lkml.kernel.org/r/20211116193247.21102-1-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ajay Garg <ajaygargnsit@gmail.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Andy Lavr <andy.lavr@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
mm/memory-failure.c | 14 +++++++++++---
mm/shmem.c | 51 +++++++++++++++++++++++++++++++++++++++++++++------
mm/userfaultfd.c | 5 +++++
3 files changed, 61 insertions(+), 9 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 05ba4b23ff52..1db0d390175a 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -57,6 +57,7 @@
#include <linux/ratelimit.h>
#include <linux/page-isolation.h>
#include <linux/pagewalk.h>
+#include <linux/shmem_fs.h>
#include "internal.h"
#include "ras/ras_event.h"
@@ -867,6 +868,7 @@ static int me_pagecache_clean(struct page_state *ps, struct page *p)
{
int ret;
struct address_space *mapping;
+ bool extra_pins;
delete_from_lru_cache(p);
@@ -895,18 +897,24 @@ static int me_pagecache_clean(struct page_state *ps, struct page *p)
goto out;
}
+ /*
+ * The shmem page is kept in page cache instead of truncating
+ * so is expected to have an extra refcount after error-handling.
+ */
+ extra_pins = shmem_mapping(mapping);
+
/*
* Truncation is a bit tricky. Enable it per file system for now.
*
* Open: to take i_rwsem or not for this? Right now we don't.
*/
ret = truncate_error_page(p, page_to_pfn(p), mapping);
+ if (has_extra_refcount(ps, p, extra_pins))
+ ret = MF_FAILED;
+
out:
unlock_page(p);
- if (has_extra_refcount(ps, p, false))
- ret = MF_FAILED;
-
return ret;
}
diff --git a/mm/shmem.c b/mm/shmem.c
index b5860f4a2738..bae56663d28d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2456,6 +2456,7 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
struct inode *inode = mapping->host;
struct shmem_inode_info *info = SHMEM_I(inode);
pgoff_t index = pos >> PAGE_SHIFT;
+ int ret = 0;
/* i_rwsem is held by caller */
if (unlikely(info->seals & (F_SEAL_GROW |
@@ -2466,7 +2467,19 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
return -EPERM;
}
- return shmem_getpage(inode, index, pagep, SGP_WRITE);
+ ret = shmem_getpage(inode, index, pagep, SGP_WRITE);
+
+ if (ret)
+ return ret;
+
+ if (PageHWPoison(*pagep)) {
+ unlock_page(*pagep);
+ put_page(*pagep);
+ *pagep = NULL;
+ return -EIO;
+ }
+
+ return 0;
}
static int
@@ -2553,6 +2566,12 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
if (sgp == SGP_CACHE)
set_page_dirty(page);
unlock_page(page);
+
+ if (PageHWPoison(page)) {
+ put_page(page);
+ error = -EIO;
+ break;
+ }
}
/*
@@ -3114,7 +3133,8 @@ static const char *shmem_get_link(struct dentry *dentry,
page = find_get_page(inode->i_mapping, 0);
if (!page)
return ERR_PTR(-ECHILD);
- if (!PageUptodate(page)) {
+ if (PageHWPoison(page) ||
+ !PageUptodate(page)) {
put_page(page);
return ERR_PTR(-ECHILD);
}
@@ -3122,6 +3142,13 @@ static const char *shmem_get_link(struct dentry *dentry,
error = shmem_getpage(inode, 0, &page, SGP_READ);
if (error)
return ERR_PTR(error);
+ if (!page)
+ return ERR_PTR(-ECHILD);
+ if (PageHWPoison(page)) {
+ unlock_page(page);
+ put_page(page);
+ return ERR_PTR(-ECHILD);
+ }
unlock_page(page);
}
set_delayed_call(done, shmem_put_link, page);
@@ -3772,6 +3799,13 @@ static void shmem_destroy_inodecache(void)
kmem_cache_destroy(shmem_inode_cachep);
}
+/* Keep the page in page cache instead of truncating it */
+static int shmem_error_remove_page(struct address_space *mapping,
+ struct page *page)
+{
+ return 0;
+}
+
const struct address_space_operations shmem_aops = {
.writepage = shmem_writepage,
.set_page_dirty = __set_page_dirty_no_writeback,
@@ -3782,7 +3816,7 @@ const struct address_space_operations shmem_aops = {
#ifdef CONFIG_MIGRATION
.migratepage = migrate_page,
#endif
- .error_remove_page = generic_error_remove_page,
+ .error_remove_page = shmem_error_remove_page,
};
EXPORT_SYMBOL(shmem_aops);
@@ -4190,9 +4224,14 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
gfp, NULL, NULL, NULL);
if (error)
- page = ERR_PTR(error);
- else
- unlock_page(page);
+ return ERR_PTR(error);
+
+ unlock_page(page);
+ if (PageHWPoison(page)) {
+ put_page(page);
+ return ERR_PTR(-EIO);
+ }
+
return page;
#else
/*
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 0e2132834bc7..5dc996bafbba 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -233,6 +233,11 @@ static int mcontinue_atomic_pte(struct mm_struct *dst_mm,
goto out;
}
+ if (PageHWPoison(page)) {
+ ret = -EIO;
+ goto out_release;
+ }
+
ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
page, false, wp_copy);
if (ret)