[PATCH 3.2 074/102] shmem: fix nlink for rename overwrite directory

[Ben Hutchings]

3.2.64-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszer...@suse.cz>

commit b928095b0a7cff7fb9fcf4c706348ceb8ab2c295 upstream.

If overwriting an empty directory with rename, then need to drop the extra
nlink.

Test prog:

#include <stdio.h>
#include <fcntl.h>
#include <err.h>
#include <sys/stat.h>

int main(void)
{
        const char *test_dir1 = "test-dir1";
        const char *test_dir2 = "test-dir2";
        int res;
        int fd;
        struct stat statbuf;

        res = mkdir(test_dir1, 0777);
        if (res == -1)
                err(1, "mkdir(\"%s\")", test_dir1);

        res = mkdir(test_dir2, 0777);
        if (res == -1)
                err(1, "mkdir(\"%s\")", test_dir2);

        fd = open(test_dir2, O_RDONLY);
        if (fd == -1)
                err(1, "open(\"%s\")", test_dir2);

        res = rename(test_dir1, test_dir2);
        if (res == -1)
                err(1, "rename(\"%s\", \"%s\")", test_dir1, test_dir2);

        res = fstat(fd, &statbuf);
        if (res == -1)
                err(1, "fstat(%i)", fd);

        if (statbuf.st_nlink != 0) {
                fprintf(stderr, "nlink is %lu, should be 0\n", 
statbuf.st_nlink);
                return 1;
        }

        return 0;
}

Signed-off-by: Miklos Szeredi <mszer...@suse.cz>
Signed-off-by: Al Viro <v...@zeniv.linux.org.uk>
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
 mm/shmem.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1719,8 +1719,10 @@ static int shmem_rename(struct inode *ol
 
        if (new_dentry->d_inode) {
                (void) shmem_unlink(new_dir, new_dentry);
-               if (they_are_dirs)
+               if (they_are_dirs) {
+                       drop_nlink(new_dentry->d_inode);
                        drop_nlink(old_dir);
+               }
        } else if (they_are_dirs) {
                drop_nlink(old_dir);
                inc_nlink(new_dir);

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