[PATCH 2/3] ext4: introduce ext4_error_remove_page

[Naoya Horiguchi]

Ext4 has its own configurable error handling policy, so it's helpful
if we can use it also in the context of memory error handling.
With this patch, when we detect a memory error on a dirty pagecache in
ext4 filesystem, we can allow users to choose to trigger kernel panic
to avoid consuming corrupted data.

Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
 fs/ext4/inode.c | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git v3.7-rc2.orig/fs/ext4/inode.c v3.7-rc2/fs/ext4/inode.c
index b3c243b..513badb 100644
--- v3.7-rc2.orig/fs/ext4/inode.c
+++ v3.7-rc2/fs/ext4/inode.c
@@ -3163,6 +3163,33 @@ static int ext4_journalled_set_page_dirty(struct page *page)
 	return __set_page_dirty_nobuffers(page);
 }
 
+static int ext4_error_remove_page(struct address_space *mapping,
+				struct page *page)
+{
+	struct inode *inode = mapping->host;
+	struct buffer_head *bh, *head;
+	ext4_fsblk_t block;
+
+	if (!PageDirty(page) || !page_has_buffers(page))
+		goto remove_page;
+
+	/* Lost data. Handle as critical fs error. */
+	bh = head = page_buffers(page);
+	do {
+		if (buffer_dirty(bh) && !buffer_delay(bh)) {
+			block = bh->b_blocknr;
+			EXT4_ERROR_INODE_BLOCK(inode, block,
+						"Removing dirty pagecache page");
+		} else
+			EXT4_ERROR_INODE(inode,
+					"Removing dirty pagecache page");
+		bh = bh->b_this_page;
+	} while (bh != head);
+
+remove_page:
+	return generic_error_remove_page(mapping, page);
+}
+
 static const struct address_space_operations ext4_ordered_aops = {
 	.readpage		= ext4_readpage,
 	.readpages		= ext4_readpages,
@@ -3175,7 +3202,7 @@ static const struct address_space_operations ext4_ordered_aops = {
 	.direct_IO		= ext4_direct_IO,
 	.migratepage		= buffer_migrate_page,
 	.is_partially_uptodate  = block_is_partially_uptodate,
-	.error_remove_page	= generic_error_remove_page,
+	.error_remove_page	= ext4_error_remove_page,
 };
 
 static const struct address_space_operations ext4_writeback_aops = {
@@ -3190,7 +3217,7 @@ static const struct address_space_operations ext4_writeback_aops = {
 	.direct_IO		= ext4_direct_IO,
 	.migratepage		= buffer_migrate_page,
 	.is_partially_uptodate  = block_is_partially_uptodate,
-	.error_remove_page	= generic_error_remove_page,
+	.error_remove_page	= ext4_error_remove_page,
 };
 
 static const struct address_space_operations ext4_journalled_aops = {
@@ -3205,7 +3232,7 @@ static const struct address_space_operations ext4_journalled_aops = {
 	.releasepage		= ext4_releasepage,
 	.direct_IO		= ext4_direct_IO,
 	.is_partially_uptodate  = block_is_partially_uptodate,
-	.error_remove_page	= generic_error_remove_page,
+	.error_remove_page	= ext4_error_remove_page,
 };
 
 static const struct address_space_operations ext4_da_aops = {
@@ -3221,7 +3248,7 @@ static const struct address_space_operations ext4_da_aops = {
 	.direct_IO		= ext4_direct_IO,
 	.migratepage		= buffer_migrate_page,
 	.is_partially_uptodate  = block_is_partially_uptodate,
-	.error_remove_page	= generic_error_remove_page,
+	.error_remove_page	= ext4_error_remove_page,
 };
 
 void ext4_set_aops(struct inode *inode)
-- 
1.7.11.7

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