From 9d8b36744935f83c5553e6f242b9961f676628ed Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 19 Feb 2024 07:27:15 +0100 Subject: shmem: document how to "persist" data when using shmem_*file_setup Add a blurb that simply dirtying the folio will persist data for in-kernel shmem files. This is what most of the callers already do. Signed-off-by: Christoph Hellwig Reviewed-by: "Matthew Wilcox (Oracle)" Reviewed-by: "Darrick J. Wong" Signed-off-by: Chandan Babu R --- mm/shmem.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'mm/shmem.c') diff --git a/mm/shmem.c b/mm/shmem.c index 95e70e9ea060..fb76da93d369 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2147,6 +2147,10 @@ unlock: * Looks up the page cache entry at @inode & @index. If a folio is * present, it is returned locked with an increased refcount. * + * If the caller modifies data in the folio, it must call folio_mark_dirty() + * before unlocking the folio to ensure that the folio is not reclaimed. + * There is no need to reserve space before calling folio_mark_dirty(). + * * When no folio is found, the behavior depends on @sgp: * - for SGP_READ, *foliop is %NULL and 0 is returned * - for SGP_NOALLOC, *foliop is %NULL and -ENOENT is returned -- cgit v1.2.3