[RFC][PATCH 04/30] fix up new filp allocators

Dave Hansen
2008-02-08T22:29:46Z

Some new uses of get_empty_filp() have crept in, and are
not properly taking mnt_want_write()s. This fixes them
up.

We really need to kill get_empty_filp().

Cc: Erez Zadok <ezk@cs.sunysb.edu>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---

linux-2.6.git-dave/fs/anon_inodes.c | 16 ++++++----------
linux-2.6.git-dave/fs/file_table.c | 6 ++++++
linux-2.6.git-dave/fs/pipe.c | 19 +++++++++----------
3 files changed, 21 insertions(+), 20 deletions(-)

diff -puN fs/anon_inodes.c~fix-up-new-filp-allocators fs/anon_inodes.c
--- linux-2.6.git/fs/anon_inodes.c~fix-up-new-filp-allocators 2008-02-08 13:04:45.000000000 -0800
+++ linux-2.6.git-dave/fs/anon_inodes.c 2008-02-08 13:04:45.000000000 -0800
@@ -81,13 +81,10 @@ int anon_inode_getfd(int *pfd, struct in

if (IS_ERR(anon_inode_inode))
return -ENODEV;
- file = get_empty_filp();
- if (!file)
- return -ENFILE;

error = get_unused_fd();
if (error < 0)
- goto err_put_filp;
+ return error;
fd = error;

/*
@@ -114,14 +111,15 @@ int anon_inode_getfd(int *pfd, struct in
dentry->d_flags &= ~DCACHE_UNHASHED;
d_instantiate(dentry, anon_inode_inode);

- file->f_path.mnt = mntget(anon_inode_mnt);
- file->f_path.dentry = dentry;
+ error = -ENFILE;
+ file = alloc_file(anon_inode_mnt, dentry,
+ FMODE_READ | FMODE_WRITE, fops);
+ if (!file)
+ goto err_put_unused_fd;
file->f_mapping = anon_inode_inode->i_mapping;

file->f_pos = 0;
file->f_flags = O_RDWR;
- file->f_op = fops;
- file->f_mode = FMODE_READ | FMODE_WRITE;
file->f_version = 0;
file->private_data = priv;

@@ -134,8 +132,6 @@ int anon_inode_getfd(int *pfd, struct in

err_put_unused_fd:
put_unused_fd(fd);
-err_put_filp:
- put_filp(file);
return error;
}
EXPORT_SYMBOL_GPL(anon_inode_getfd);
diff -puN fs/file_table.c~fix-up-new-filp-allocators fs/file_table.c
--- linux-2.6.git/fs/file_table.c~fix-up-new-filp-allocators 2008-02-08 13:04:45.000000000 -0800
+++ linux-2.6.git-dave/fs/file_table.c 2008-02-08 13:04:45.000000000 -0800
@@ -83,6 +83,12 @@ int proc_nr_files(ctl_table *table, int
/* Find an unused file structure and return a pointer to it.
* Returns NULL, if there are no more free file structures or
* we run out of memory.
+ *
+ * Be very careful using this. You are responsible for
+ * getting write access to any mount that you might assign
+ * to this filp, if it is opened for write. If this is not
+ * done, you will imbalance int the mount's writer count
+ * and a warning at __fput() time.
*/
struct file *get_empty_filp(void)
{
diff -puN fs/pipe.c~fix-up-new-filp-allocators fs/pipe.c
--- linux-2.6.git/fs/pipe.c~fix-up-new-filp-allocators 2008-02-08 13:04:45.000000000 -0800
+++ linux-2.6.git-dave/fs/pipe.c 2008-02-08 13:04:45.000000000 -0800
@@ -959,13 +959,10 @@ struct file *create_write_pipe(void)
struct dentry *dentry;
struct qstr name = { .name = "" };

- f = get_empty_filp();
- if (!f)
- return ERR_PTR(-ENFILE);
err = -ENFILE;
inode = get_pipe_inode();
if (!inode)
- goto err_file;
+ goto err;

err = -ENOMEM;
dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
@@ -980,22 +977,24 @@ struct file *create_write_pipe(void)
*/
dentry->d_flags &= ~DCACHE_UNHASHED;
d_instantiate(dentry, inode);
- f->f_path.mnt = mntget(pipe_mnt);
- f->f_path.dentry = dentry;
+
+ err = -ENFILE;
+ f = alloc_file(pipe_mnt, dentry, FMODE_WRITE, &write_pipe_fops);
+ if (!f)
+ goto err_dentry;
f->f_mapping = inode->i_mapping;

f->f_flags = O_WRONLY;
- f->f_op = &write_pipe_fops;
- f->f_mode = FMODE_WRITE;
f->f_version = 0;

return f;

+ err_dentry:
+ dput(dentry);
err_inode:
free_pipe_info(inode);
iput(inode);
- err_file:
- put_filp(f);
+ err:
return ERR_PTR(err);
}

_