6.6-stable review patch. If anyone has any objections, please let me know.
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From: Vishal Moola (Oracle) vishal.moola@gmail.com
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) vishal.moola@gmail.com Reported-by: Qu Wenruo quwenruo.btrfs@gmx.com Closes: https://lkml.kernel.org/r/b714e4de-2583-4035-b829-72cfb5eb6fc6@gmx.com Tested-by: Qu Wenruo quwenruo.btrfs@gmx.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Vivek Kasireddy vivek.kasireddy@intel.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/filemap.c | 1 + 1 file changed, 1 insertion(+)
--- a/mm/filemap.c +++ b/mm/filemap.c @@ -2256,6 +2256,7 @@ unsigned filemap_get_folios_contig(struc *start = folio->index + nr; goto out; } + xas_advance(&xas, folio_next_index(folio) - 1); continue; put_folio: folio_put(folio);