[PATCH] tmpfs: Restore functionality of nr_inodes=0

[Byron Stanoszek]

Commit e809d5f0b5c9 ("tmpfs: per-superblock i_ino support") made changes to
shmem_reserve_inode() in mm/shmem.c, however the original test for
(sbinfo->max_inodes) got dropped. This causes mounting tmpfs with option
nr_inodes=0 to fail:

  # mount -ttmpfs -onr_inodes=0 none /ext0
  mount: /ext0: mount(2) system call failed: Cannot allocate memory.

This patch restores the nr_inodes=0 functionality.

Fixes: e809d5f0b5c9 ("tmpfs: per-superblock i_ino support")
Cc: Chris Down <ch...@chrisdown.name>
Signed-off-by: Byron Stanoszek <gand...@winds.org>
---
 mm/shmem.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 271548ca20f3..8e2b35ba93ad 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -279,11 +279,13 @@ static int shmem_reserve_inode(struct super_block *sb, 
ino_t *inop)
 
        if (!(sb->s_flags & SB_KERNMOUNT)) {
                spin_lock(&sbinfo->stat_lock);
-               if (!sbinfo->free_inodes) {
-                       spin_unlock(&sbinfo->stat_lock);
-                       return -ENOSPC;
+               if (sbinfo->max_inodes) {
+                       if (!sbinfo->free_inodes) {
+                               spin_unlock(&sbinfo->stat_lock);
+                               return -ENOSPC;
+                       }
+                       sbinfo->free_inodes--;
                }
-               sbinfo->free_inodes--;
                if (inop) {
                        ino = sbinfo->next_ino++;
                        if (unlikely(is_zero_ino(ino)))
-- 
2.28.0