tmpfs: use kmemdup for short symlinks

But we've not yet removed the old swp_entry_t i_direct[16] from
shmem_inode_info.  That's because it was still being shared with the
inline symlink.  Remove it now (saving 64 or 128 bytes from shmem inode
size), and use kmemdup() for short symlinks, say, those up to 128 bytes.

I wonder why mpol_free_shared_policy() is done in shmem_destroy_inode()
rather than shmem_evict_inode(), where we usually do such freeing? I
guess it doesn't matter, and I'm not into NUMA mpol testing right now.

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 8 deletions

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 0c8e952df594..9291ac3cc627 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -8,20 +8,15 @@
 
 /* inode in-kernel data */
 
-#define SHMEM_NR_DIRECT 16
-
-#define SHMEM_SYMLINK_INLINE_LEN (SHMEM_NR_DIRECT * sizeof(swp_entry_t))
-
 struct shmem_inode_info {
         spinlock_t              lock;
         unsigned long           flags;
         unsigned long           alloced;        /* data pages alloced to file */
-        unsigned long           swapped;        /* subtotal assigned to swap */
-        struct shared_policy    policy;         /* NUMA memory alloc policy */
         union {
-                swp_entry_t     i_direct[SHMEM_NR_DIRECT]; /* first blocks */
-                char            inline_symlink[SHMEM_SYMLINK_INLINE_LEN];
+                unsigned long   swapped;        /* subtotal assigned to swap */
+                char            *symlink;       /* unswappable short symlink */
         };
+        struct shared_policy    policy;         /* NUMA memory alloc policy */
         struct list_head        swaplist;       /* chain of maybes on swap */
         struct list_head        xattr_list;     /* list of shmem_xattr */
         struct inode            vfs_inode;