filemap_get_folios_contig() is supposed to return distinct folios
found within [start, end]. Large folios in the Xarray become multi-index
entries. xas_next() can iterate through the sub-indexes before finding
a sibling entry and breaking out of the loop.
This can result in a returned folio_batch containing an indeterminate
number of duplicate folios, which forces the callers to skeptically
handle the returned batch. This is inefficient and incurs a large
maintenance overhead.
We can fix this by calling xas_advance() after we have successfully
adding a folio to the batch to ensure our Xarray is positioned such that
it will correctly find the next folio - similar to
filemap_get_read_batch().
Fixes: 35b471467f88 ("filemap: add filemap_get_folios_contig()")
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
mm/filemap.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/filemap.c b/mm/filemap.c
index cc69f174f76b..bc7b28dfba3c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2233,6 +2233,7 @@ unsigned filemap_get_folios_contig(struct address_space *mapping,
*start = folio->index + nr;
goto out;
}
+ xas_advance(&xas, folio_next_index(folio) - 1);
continue;
put_folio:
folio_put(folio);
--
2.48.1
--jdO5iHBsjAZEVpV9--
