From: Jan Kara jack@suse.cz
commit 1571c029a2ff289683ddb0a32253850363bcb8a7 upstream.
When inserting entry into xarray, we store mapping and index in corresponding struct pages for memory error handling. When it happened that one process was mapping file at PMD granularity while another process at PTE granularity, we could wrongly deassociate PMD range and then reassociate PTE range leaving the rest of struct pages in PMD range without mapping information which could later cause missed notifications about memory errors. Fix the problem by calling the association / deassociation code if and only if we are really going to update the xarray (deassociating and associating zero or empty entries is just no-op so there's no reason to complicate the code with trying to avoid the calls for these cases).
Cc: stable@vger.kernel.org Fixes: d2c997c0f145 ("fs, dax: use page->mapping to warn if truncate...") Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/dax.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
--- a/fs/dax.c +++ b/fs/dax.c @@ -728,12 +728,11 @@ static void *dax_insert_entry(struct xa_
xas_reset(xas); xas_lock_irq(xas); - if (dax_entry_size(entry) != dax_entry_size(new_entry)) { + if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) { + void *old; + dax_disassociate_entry(entry, mapping, false); dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address); - } - - if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) { /* * Only swap our new entry into the page cache if the current * entry is a zero page or an empty entry. If a normal PTE or @@ -742,7 +741,7 @@ static void *dax_insert_entry(struct xa_ * existing entry is a PMD, we will just leave the PMD in the * tree and dirty it if necessary. */ - void *old = dax_lock_entry(xas, new_entry); + old = dax_lock_entry(xas, new_entry); WARN_ON_ONCE(old != xa_mk_value(xa_to_value(entry) | DAX_LOCKED)); entry = new_entry;