mm: shmem: don't truncate page if memory failure happens

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.

[arnd@arndb.de: fix uninitialized variable use in me_pagecache_clean()]
Link: https://lkml.kernel.org/r/20211022064748.4173718-1-arnd@kernel.org
Link: https://lkml.kernel.org/r/20211020210755.23964-6-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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index bbd433e9679083f1e5022bd510a8b6cd3d8e9ba0..952a41d568c46940af1fe89b44a3c0637a418458 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -58,6 +58,7 @@
 #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 df2f0288b9caa57af014c8d382d95a64e8c1d5d2..6a7bb46019e2c58096d172c56519d1f15a604966 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2454,6 +2454,7 @@ 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 |
@@ -2464,7 +2465,15 @@ 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 (*pagep && PageHWPoison(*pagep)) {
+               unlock_page(*pagep);
+               put_page(*pagep);
+               ret = -EIO;
+       }
+
+       return ret;
 }
 
 static int
@@ -2551,6 +2560,12 @@ 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;
+                       }
                }
 
                /*
@@ -3112,7 +3127,8 @@ 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);
                }
@@ -3120,6 +3136,11 @@ 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 && PageHWPoison(page)) {
+                       unlock_page(page);
+                       put_page(page);
+                       return ERR_PTR(-ECHILD);
+               }
                unlock_page(page);
        }
        set_delayed_call(done, shmem_put_link, page);
@@ -3770,6 +3791,13 @@ 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,
@@ -3780,7 +3808,7 @@ 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);
 
@@ -4191,6 +4219,10 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
                page = ERR_PTR(error);
        else
                unlock_page(page);
+
+       if (PageHWPoison(page))
+               page = ERR_PTR(-EIO);
+
        return page;
 #else
        /*

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index caf6dfff2a60f7d582a8e00da67489919d5d86e8..77fce86371a95a8eb212c96e3e59f72ef305d652 100644 (file)
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -232,6 +232,11 @@ 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)