HWPOISON: Enable .remove_error_page for migration aware file systems

Enable removing of corrupted pages through truncation
for a bunch of file systems: ext*, xfs, gfs2, ocfs2, ntfs
These should cover most server needs.

I chose the set of migration aware file systems for this
for now, assuming they have been especially audited.
But in general it should be safe for all file systems
on the data area that support read/write and truncate.

Caveat: the hardware error handler does not take i_mutex
for now before calling the truncate function. Is that ok?

Cc: tytso@mit.edu
Cc: hch@infradead.org
Cc: mfasheh@suse.com
Cc: aia21@cantab.net
Cc: hugh.dickins@tiscali.co.uk
Cc: swhiteho@redhat.com
Signed-off-by: Andi Kleen <ak@linux.intel.com>

mm/shmem.c

@@ -2421,6 +2421,7 @@ static const struct address_space_operations shmem_aops = {
 	.write_end	= shmem_write_end,
 #endif
 	.migratepage	= migrate_page,
+	.error_remove_page = generic_error_remove_page,
 };
 
 static const struct file_operations shmem_file_operations = {