From 8338e0723fbf98c0fdf033652903640454770c68 Mon Sep 17 00:00:00 2001 From: "Vishal Moola (Oracle)" Date: Thu, 3 Apr 2025 16:54:17 -0700 Subject: [PATCH] mm: fix filemap_get_folios_contig returning batches of identical folios commit 8ab1b16023961dc640023b10436d282f905835ad upstream. 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(). Link: https://lkml.kernel.org/r/Z-8s1-kiIDkzgRbc@fedora Fixes: 35b471467f88 ("filemap: add filemap_get_folios_contig()") Signed-off-by: Vishal Moola (Oracle) Reported-by: Qu Wenruo Closes: https://lkml.kernel.org/r/b714e4de-2583-4035-b829-72cfb5eb6fc6@gmx.com Tested-by: Qu Wenruo Cc: Matthew Wilcox (Oracle) Cc: Vivek Kasireddy Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/filemap.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/filemap.c b/mm/filemap.c index 3c37ad6c598b..fa18e71f9c88 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2222,6 +2222,7 @@ 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);