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 <hch@xxxxxx> Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx> --- mm/shmem.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/shmem.c b/mm/shmem.c index e89fb5eccb0c0a..f7d6848fb294d6 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2150,6 +2150,11 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index, * * Return: The found folio, %NULL if SGP_READ or SGP_NOALLOC was passed in @sgp * and no folio was found at @index, or an ERR_PTR() otherwise. + * + * If the caller modifies data in the returned folio, it must call + * folio_mark_dirty() on the locked folio before dropping the reference to + * ensure the folio is not reclaimed. Unlike for normal file systems there is + * no need to reserve space for users of shmem_*file_setup(). */ int shmem_get_folio(struct inode *inode, pgoff_t index, struct folio **foliop, enum sgp_type sgp) -- 2.39.2
