[PATCH] tmpfs: use ida to get inode number

[zhengbin <zhengbin13@huawei.com>]

Use a script to test tmpfs, after 10 days, there will be files share the
same inode number, thus bug happens.
The script is as follows:
while(1) {
  create a file
  dlopen it
  ...
  remove it
}

I have tried to change last_ino type to unsigned long, while this was
rejected, see details on https://patchwork.kernel.org/patch/11023915.

Use ida to get inode number, from the fs_mark test, performance impact
is small.

CPU core: 128  memory: 8G
Use fs_mark to create ten million files first in tmpfs.

Then test performance in the following command(test five times):
rm -rf /tmp/fsmark_test
sync
echo 3 > /proc/sys/vm/drop_caches
sleep 10
fs_mark -t 20 -s 0 -n 102400 -D 64 -N 1600 -L 3 -d /tmp/fsmark_test

result is file creation speed(Files/sec).
get_next_ino  |  use ida
439506.7      |  423219.0
441453.0      |  406832.7
439868.0      |  441283.3
445642.3      |  428221.3
441776.7      |  438129.0
average:
441649.34     |  427537.06

Signed-off-by: zhengbin <zhengbin13@huawei.com>
---
 mm/shmem.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 5b93877..6b5e01b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -258,6 +258,7 @@ static const struct inode_operations shmem_dir_inode_operations;
 static const struct inode_operations shmem_special_inode_operations;
 static const struct vm_operations_struct shmem_vm_ops;
 static struct file_system_type shmem_fs_type;
+static DEFINE_IDA(shmem_inode_ida);

 bool vma_is_shmem(struct vm_area_struct *vma)
 {
@@ -1138,6 +1139,7 @@ static void shmem_evict_inode(struct inode *inode)

 	simple_xattrs_free(&info->xattrs);
 	WARN_ON(inode->i_blocks);
+	ida_simple_remove(&shmem_inode_ida, inode->i_ino);
 	shmem_free_inode(inode->i_sb);
 	clear_inode(inode);
 }
@@ -2213,13 +2215,20 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
 	struct inode *inode;
 	struct shmem_inode_info *info;
 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
+	int i_ino;

 	if (shmem_reserve_inode(sb))
 		return NULL;

+	i_ino = ida_simple_get(&shmem_inode_ida, 0, 0, GFP_KERNEL);
+	if (i_ino < 0) {
+		shmem_free_inode(sb);
+		return NULL;
+	}
+
 	inode = new_inode(sb);
 	if (inode) {
-		inode->i_ino = get_next_ino();
+		inode->i_ino = i_ino;
 		inode_init_owner(inode, dir, mode);
 		inode->i_blocks = 0;
 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
@@ -2263,8 +2272,11 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
 		}

 		lockdep_annotate_inode_mutex_key(inode);
-	} else
+	} else {
+		ida_simple_remove(&shmem_inode_ida, i_ino);
 		shmem_free_inode(sb);
+	}
+
 	return inode;
 }

--
2.7.4