Commit 1571c029 authored Jun 06, 2019 by Jan Kara Committed by Dan Williams Jun 06, 2019

dax: Fix xarray entry association for mixed mappings



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: d2c997c0 ("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>

parent f2c7c76c

fs/dax.c

+4 −5

Original line number	Diff line number	Diff line
		@@ -728,12 +728,11 @@ static void dax_insert_entry(struct xa_state xas,

		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_state xas,
		* 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;

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