From: Vishal Moola (Oracle) Date: Thu, 3 Apr 2025 23:54:17 +0000 (-0700) Subject: mm: fix filemap_get_folios_contig returning batches of identical folios X-Git-Tag: v6.15-rc3~43^2~6 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8ab1b16023961dc640023b10436d282f905835ad;p=thirdparty%2Flinux.git mm: fix filemap_get_folios_contig returning batches of identical folios 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 --- diff --git a/mm/filemap.c b/mm/filemap.c index b5e784f34d980..7b90cbeb4a1ad 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2244,6 +2244,7 @@ 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);