tmpfs: don't enable large folios if not supported

tmpfs can support large folios, but there are some configurable options
(mount options and runtime deny/force) to enable/disable large folio
allocation, so there is a performance issue when performing writes without
large folios.  The issue is similar to commit 4e527d5841e2 ("iomap: fault
in smaller chunks for non-large folio mappings").

Since 'deny' is for emergencies and 'force' is for testing, performance
issues should not be a problem in real production environments, so don't
call mapping_set_large_folios() in __shmem_get_inode() when large folio is
disabled with mount huge=never option (default policy).

Link: https://lkml.kernel.org/r/20241017141742.1169404-1-wangkefeng.wang@huawei.com
Fixes: 9aac777aaf94 ("filemap: Convert generic_perform_write() to support large folios")
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/shmem.c b/mm/shmem.c
index 6ad50ba60d8ef90bcb97a178580169aecbc06a41..98fb539434f497ff6c1c512148e010e177a3f427 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2842,7 +2842,10 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap,
        cache_no_acl(inode);
        if (sbinfo->noswap)
                mapping_set_unevictable(inode->i_mapping);
-       mapping_set_large_folios(inode->i_mapping);
+
+       /* Don't consider 'deny' for emergencies and 'force' for testing */
+       if (sbinfo->huge)
+               mapping_set_large_folios(inode->i_mapping);
 
        switch (mode & S_IFMT) {
        default: