On Sat, Feb 18, 2023 at 09:02:42AM +0100, gregkh@linuxfoundation.org wrote:

The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Here's a patch for 5.15-stable, generated against v5.15.94

diff --git a/mm/filemap.c b/mm/filemap.c index 30c9c2a63746..81e28722edfa 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2538,18 +2538,19 @@ static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter, struct page *page; int err = 0;

+ /* "last_index" is the index of the page beyond the end of the read */ last_index = DIV_ROUND_UP(iocb->ki_pos + iter->count, PAGE_SIZE); retry: if (fatal_signal_pending(current)) return -EINTR;

- filemap_get_read_batch(mapping, index, last_index, pvec); + filemap_get_read_batch(mapping, index, last_index - 1, pvec); if (!pagevec_count(pvec)) { if (iocb->ki_flags & IOCB_NOIO) return -EAGAIN; page_cache_sync_readahead(mapping, ra, filp, index, last_index - index); - filemap_get_read_batch(mapping, index, last_index, pvec); + filemap_get_read_batch(mapping, index, last_index - 1, pvec); } if (!pagevec_count(pvec)) { if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))

Possible dependencies:

5956592ce337 ("mm/filemap: fix page end in filemap_get_read_batch") 25d6a23e8d28 ("filemap: Convert filemap_get_read_batch() to use a folio_batch") d996fc7f615f ("filemap: Convert filemap_read() to use a folio") 65bca53b5f63 ("filemap: Convert filemap_get_pages to use folios") a5d4ad098528 ("filemap: Convert filemap_create_page to folio") 9d427b4eb456 ("filemap: Convert filemap_read_page to take a folio") bdb729329769 ("filemap: Convert filemap_get_read_batch to use folios") 512b7931ad05 ("Merge branch 'akpm' (patches from Andrew)")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

...

From 5956592ce337330cdff0399a6f8b6a5aea397a8e Mon Sep 17 00:00:00 2001

From: Qian Yingjin qian@ddn.com Date: Wed, 8 Feb 2023 10:24:00 +0800 Subject: [PATCH] mm/filemap: fix page end in filemap_get_read_batch

I was running traces of the read code against an RAID storage system to understand why read requests were being misaligned against the underlying RAID strips. I found that the page end offset calculation in filemap_get_read_batch() was off by one.

When a read is submitted with end offset 1048575, then it calculates the end page for read of 256 when it should be 255. "last_index" is the index of the page beyond the end of the read and it should be skipped when get a batch of pages for read in @filemap_get_read_batch().

The below simple patch fixes the problem. This code was introduced in kernel 5.12.

Link: https://lkml.kernel.org/r/20230208022400.28962-1-coolqyj@163.com Fixes: cbd59c48ae2b ("mm/filemap: use head pages in generic_file_buffered_read") Signed-off-by: Qian Yingjin qian@ddn.com Reviewed-by: Matthew Wilcox (Oracle) willy@infradead.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org

diff --git a/mm/filemap.c b/mm/filemap.c index c4d4ace9cc70..0e20a8d6dd93 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2588,18 +2588,19 @@ static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter, struct folio *folio; int err = 0;

• /* "last_index" is the index of the page beyond the end of the read */ last_index = DIV_ROUND_UP(iocb->ki_pos + iter->count, PAGE_SIZE);

retry: if (fatal_signal_pending(current)) return -EINTR;

• filemap_get_read_batch(mapping, index, last_index, fbatch);

• filemap_get_read_batch(mapping, index, last_index - 1, fbatch); if (!folio_batch_count(fbatch)) { if (iocb->ki_flags & IOCB_NOIO) return -EAGAIN; page_cache_sync_readahead(mapping, ra, filp, index, last_index - index);

• filemap_get_read_batch(mapping, index, last_index, fbatch);
  

• filemap_get_read_batch(mapping, index, last_index - 1, fbatch);
  

  } if (!folio_batch_count(fbatch)) { if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))