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XArray: Update the LRU list in xas_split() 

When splitting a value entry, we may need to add the new nodes to the LRU
list and remove the parent node from the LRU list.  The WARN_ON checks
in shadow_lru_isolate() catch this oversight.  This bug was latent
until we stopped splitting folios in shrink_page_list() with commit
820c4e2e6f ("mm/vmscan: Free non-shmem folios without splitting them").
That allows the creation of large shadow entries, and subsequently when
trying to page in a small page, we will split the large shadow entry
in __filemap_add_folio().

Fixes: 8fc75643c5 ("XArray: add xas_split")
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2022-03-31 08:27:09 -04:00
parent 3e3c658055
commit 3ed4bb7715
1 changed files with 2 additions and 0 deletions
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2
lib/xarray.c
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@ -1081,6 +1081,7 @@ void xas_split(struct xa_state *xas, void *entry, unsigned int order)
xa_mk_node(child));
if (xa_is_value(curr))
values--;
xas_update(xas, child);
} else {
unsigned int canon = offset - xas->xa_sibs;
@ -1095,6 +1096,7 @@ void xas_split(struct xa_state *xas, void *entry, unsigned int order)
} while (offset-- > xas->xa_offset);
node->nr_values += values;
xas_update(xas, node);
}
EXPORT_SYMBOL_GPL(xas_split);
#endif