6.16-stable review patch. If anyone has any objections, please let me know.
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From: Chi Zhiling chizhiling@kylinos.cn
commit bbcaee20e03ecaeeecba32a703816a0d4502b6c4 upstream.
max_scan in page_cache_next_miss always decreases to zero when no hole is found, causing the return value to be index + 0.
Fix this by preserving the max_scan value throughout the loop.
Jan said "From what I know and have seen in the past, wrong responses from page_cache_next_miss() can lead to readahead window reduction and thus reduced read speeds."
Link: https://lkml.kernel.org/r/20250605054935.2323451-1-chizhiling@163.com Fixes: 901a269ff3d5 ("filemap: fix page_cache_next_miss() when no hole found") Signed-off-by: Chi Zhiling chizhiling@kylinos.cn Reviewed-by: Jan Kara jack@suse.cz Cc: Josef Bacik josef@toxicpanda.com Cc: Matthew Wilcox (Oracle) willy@infradead.org 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 | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/filemap.c +++ b/mm/filemap.c @@ -1778,8 +1778,9 @@ pgoff_t page_cache_next_miss(struct addr pgoff_t index, unsigned long max_scan) { XA_STATE(xas, &mapping->i_pages, index); + unsigned long nr = max_scan;
- while (max_scan--) { + while (nr--) { void *entry = xas_next(&xas); if (!entry || xa_is_value(entry)) return xas.xa_index;