[PATCH] ext3: Don't warn from writepage when readonly inode is spotted after error

[Jan Kara <jack@suse.cz>]

WARN_ON_ONCE(IS_RDONLY(inode)) tends to trip when filesystem hits error and is
remounted read-only. This unnecessarily scares users (well, they should be
scared because of filesystem error, but the stack trace distracts them from the
right source of their fear ;-). We could as well just remove the WARN_ON but
it's not hard to fix it to not trip on filesystem with errors and not use more
cycles in the common case so that's what we do.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext3/inode.c |   18 +++++++++++++++---
 1 files changed, 15 insertions(+), 3 deletions(-)

  I carry this patch in my tree and will merge it with Linus in the next merge
window if noone objects.

diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index a8d3217..91ac85b 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -1623,7 +1623,11 @@ static int ext3_ordered_writepage(struct page *page,
 	int err;
 
 	J_ASSERT(PageLocked(page));
-	WARN_ON_ONCE(IS_RDONLY(inode));
+	/*
+	 * We don't want to warn for emergency remount. The condition is ordered to avoid
+	 * dereferencing inode->i_sb in non-error case to avoid slow-downs.
+	 */
+	WARN_ON_ONCE(IS_RDONLY(inode) && !(EXT3_SB(inode->i_sb)->s_mount_state & EXT3_ERROR_FS));
 
 	/*
 	 * We give up here if we're reentered, because it might be for a
@@ -1698,7 +1702,11 @@ static int ext3_writeback_writepage(struct page *page,
 	int err;
 
 	J_ASSERT(PageLocked(page));
-	WARN_ON_ONCE(IS_RDONLY(inode));
+	/*
+	 * We don't want to warn for emergency remount. The condition is ordered to avoid
+	 * dereferencing inode->i_sb in non-error case to avoid slow-downs.
+	 */
+	WARN_ON_ONCE(IS_RDONLY(inode) && !(EXT3_SB(inode->i_sb)->s_mount_state & EXT3_ERROR_FS));
 
 	if (ext3_journal_current_handle())
 		goto out_fail;
@@ -1741,7 +1749,11 @@ static int ext3_journalled_writepage(struct page *page,
 	int err;
 
 	J_ASSERT(PageLocked(page));
-	WARN_ON_ONCE(IS_RDONLY(inode));
+	/*
+	 * We don't want to warn for emergency remount. The condition is ordered to avoid
+	 * dereferencing inode->i_sb in non-error case to avoid slow-downs.
+	 */
+	WARN_ON_ONCE(IS_RDONLY(inode) && !(EXT3_SB(inode->i_sb)->s_mount_state & EXT3_ERROR_FS));
 
 	if (ext3_journal_current_handle())
 		goto no_write;
-- 
1.7.1