The patch below does not apply to the 6.6-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.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 1f789a45c3f1aa77531db21768fca70b66c0eeb1 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024071531-junkyard-cornea-9a80@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

1f789a45c3f1 ("mm/readahead: limit page cache size in page_cache_ra_order()") e03c16fb4af1 ("readahead: use ilog2 instead of a while loop in page_cache_ra_order()")

thanks,

greg k-h

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

From 1f789a45c3f1aa77531db21768fca70b66c0eeb1 Mon Sep 17 00:00:00 2001 From: Gavin Shan gshan@redhat.com Date: Thu, 27 Jun 2024 10:39:50 +1000 Subject: [PATCH] mm/readahead: limit page cache size in page_cache_ra_order()

In page_cache_ra_order(), the maximal order of the page cache to be allocated shouldn't be larger than MAX_PAGECACHE_ORDER. Otherwise, it's possible the large page cache can't be supported by xarray when the corresponding xarray entry is split.

For example, HPAGE_PMD_ORDER is 13 on ARM64 when the base page size is 64KB. The PMD-sized page cache can't be supported by xarray.

Link: https://lkml.kernel.org/r/20240627003953.1262512-3-gshan@redhat.com Fixes: 793917d997df ("mm/readahead: Add large folio readahead") Signed-off-by: Gavin Shan gshan@redhat.com Acked-by: David Hildenbrand david@redhat.com Cc: Darrick J. Wong djwong@kernel.org Cc: Don Dutile ddutile@redhat.com Cc: Hugh Dickins hughd@google.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Ryan Roberts ryan.roberts@arm.com Cc: William Kucharski william.kucharski@oracle.com Cc: Zhenyu Zhang zhenyzha@redhat.com Cc: stable@vger.kernel.org [5.18+] Signed-off-by: Andrew Morton akpm@linux-foundation.org

diff --git a/mm/readahead.c b/mm/readahead.c index c1b23989d9ca..817b2a352d78 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -503,11 +503,11 @@ void page_cache_ra_order(struct readahead_control *ractl,

limit = min(limit, index + ra->size - 1);

- if (new_order < MAX_PAGECACHE_ORDER) { + if (new_order < MAX_PAGECACHE_ORDER) new_order += 2; - new_order = min_t(unsigned int, MAX_PAGECACHE_ORDER, new_order); - new_order = min_t(unsigned int, new_order, ilog2(ra->size)); - } + + new_order = min_t(unsigned int, MAX_PAGECACHE_ORDER, new_order); + new_order = min_t(unsigned int, new_order, ilog2(ra->size));

/* See comment in page_cache_ra_unbounded() */ nofs = memalloc_nofs_save();