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

This reverts commit b9d02f1.

The error handling of that patch was fundamentally broken, and it needs
to be entirely re-done.

For example, in shmem_write_begin() it would call shmem_getpage(), then
ignore the error return from that, and look at the page pointer contents
instead.

And in shmem_read_mapping_page_gfp(), the patch tested PageHWPoison() on
a page pointer that two lines earlier had potentially been set as an
error pointer.

These issues could be individually fixed, but when it has this many
issues, I'm just reverting it instead of waiting for fixes.

Link: https://lore.kernel.org/linux-mm/20211111084617.6746-1-ajaygargnsit@gmail.com/
Reported-by: Ajay Garg <ajaygargnsit@gmail.com>
Reported-by: Jens Axboe <axboe@kernel.dk>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: torvalds

mm/memory-failure.c

@@ -58,7 +58,6 @@
 #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"
 
@@ -868,7 +867,6 @@ 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);
 
@@ -897,24 +895,18 @@ 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;
 }
 

mm/shmem.c

@@ -2456,7 +2456,6 @@ 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 |
@@ -2467,15 +2466,7 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
 			return -EPERM;
 	}
 
-	ret = shmem_getpage(inode, index, pagep, SGP_WRITE);
-
-	if (*pagep && PageHWPoison(*pagep)) {
-		unlock_page(*pagep);
-		put_page(*pagep);
-		ret = -EIO;
-	}
-
-	return ret;
+	return shmem_getpage(inode, index, pagep, SGP_WRITE);
 }
 
 static int
@@ -2562,12 +2553,6 @@ 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;
-			}
 		}
 
 		/*
@@ -3107,20 +3092,14 @@ static const char *shmem_get_link(struct dentry *dentry,
 		page = find_get_page(inode->i_mapping, 0);
 		if (!page)
 			return ERR_PTR(-ECHILD);
-		if (PageHWPoison(page) ||
-		    !PageUptodate(page)) {
+		if (!PageUptodate(page)) {
 			put_page(page);
 			return ERR_PTR(-ECHILD);
 		}
 	} else {
 		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);
@@ -3771,13 +3750,6 @@ 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,
@@ -3788,7 +3760,7 @@ const struct address_space_operations shmem_aops = {
 #ifdef CONFIG_MIGRATION
 	.migratepage	= migrate_page,
 #endif
-	.error_remove_page = shmem_error_remove_page,
+	.error_remove_page = generic_error_remove_page,
 };
 EXPORT_SYMBOL(shmem_aops);
 
@@ -4199,10 +4171,6 @@ 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
 	/*

mm/userfaultfd.c

@@ -232,11 +232,6 @@ 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)