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Subject[PATCH 04/21] vfs: add lookup_open()
Date
From: Miklos Szeredi <mszeredi@suse.cz>

Split out lookup + maybe create from do_last(). This is the part under i_mutex
protection.

The function is called lookup_open() and returns a filp even though the open
part is not used yet.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/namei.c | 99 +++++++++++++++++++++++++++++++++++++-----------------------
1 files changed, 61 insertions(+), 38 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 0a56b61..1153476 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2188,19 +2188,73 @@ static inline int open_to_namei_flags(int flag)
}

/*
+ * Lookup, maybe create and open the last component
+ *
+ * Must be called with i_mutex held on parent.
+ *
+ * Returns open file or NULL on success, error otherwise. NULL means no open
+ * was performed, only lookup.
+ */
+static struct file *lookup_open(struct nameidata *nd, struct path *path,
+ const struct open_flags *op,
+ int *want_write, bool *created)
+{
+ struct dentry *dir = nd->path.dentry;
+ struct dentry *dentry;
+ int error;
+
+ *created = false;
+ dentry = lookup_hash(nd);
+ if (IS_ERR(dentry))
+ return ERR_CAST(dentry);
+
+ /* Negative dentry, just create the file */
+ if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
+ umode_t mode = op->mode;
+ if (!IS_POSIXACL(dir->d_inode))
+ mode &= ~current_umask();
+ /*
+ * This write is needed to ensure that a
+ * rw->ro transition does not occur between
+ * the time when the file is created and when
+ * a permanent write count is taken through
+ * the 'struct file' in nameidata_to_filp().
+ */
+ error = mnt_want_write(nd->path.mnt);
+ if (error)
+ goto out_dput;
+ *want_write = 1;
+ *created = true;
+ error = security_path_mknod(&nd->path, dentry, mode, 0);
+ if (error)
+ goto out_dput;
+ error = vfs_create(dir->d_inode, dentry, mode, nd);
+ if (error)
+ goto out_dput;
+ }
+ path->dentry = dentry;
+ path->mnt = nd->path.mnt;
+ return NULL;
+
+out_dput:
+ dput(dentry);
+ return ERR_PTR(error);
+}
+
+/*
* Handle the last step of open()
*/
static struct file *do_last(struct nameidata *nd, struct path *path,
const struct open_flags *op, const char *pathname)
{
struct dentry *dir = nd->path.dentry;
- struct dentry *dentry;
int open_flag = op->open_flag;
int will_truncate = open_flag & O_TRUNC;
int want_write = 0;
int acc_mode = op->acc_mode;
struct file *filp;
struct inode *inode;
+ bool created;
int symlink_ok = 0;
struct path save_parent = { .dentry = NULL, .mnt = NULL };
bool retried = false;
@@ -2268,53 +2322,24 @@ static struct file *do_last(struct nameidata *nd, struct path *path,

retry_lookup:
mutex_lock(&dir->d_inode->i_mutex);
+ filp = lookup_open(nd, path, op, &want_write, &created);
+ mutex_unlock(&dir->d_inode->i_mutex);

- dentry = lookup_hash(nd);
- error = PTR_ERR(dentry);
- if (IS_ERR(dentry)) {
- mutex_unlock(&dir->d_inode->i_mutex);
- goto exit;
- }
-
- path->dentry = dentry;
- path->mnt = nd->path.mnt;
+ if (IS_ERR(filp))
+ goto out;

- /* Negative dentry, just create the file */
- if (!dentry->d_inode && (open_flag & O_CREAT)) {
- umode_t mode = op->mode;
- if (!IS_POSIXACL(dir->d_inode))
- mode &= ~current_umask();
- /*
- * This write is needed to ensure that a
- * rw->ro transition does not occur between
- * the time when the file is created and when
- * a permanent write count is taken through
- * the 'struct file' in nameidata_to_filp().
- */
- error = mnt_want_write(nd->path.mnt);
- if (error)
- goto exit_mutex_unlock;
- want_write = 1;
+ if (created) {
/* Don't check for write permission, don't truncate */
open_flag &= ~O_TRUNC;
will_truncate = 0;
acc_mode = MAY_OPEN;
- error = security_path_mknod(&nd->path, dentry, mode, 0);
- if (error)
- goto exit_mutex_unlock;
- error = vfs_create(dir->d_inode, dentry, mode, nd);
- if (error)
- goto exit_mutex_unlock;
- mutex_unlock(&dir->d_inode->i_mutex);
- dput(nd->path.dentry);
- nd->path.dentry = dentry;
+ path_to_nameidata(path, nd);
goto common;
}

/*
* It already exists.
*/
- mutex_unlock(&dir->d_inode->i_mutex);
audit_inode(pathname, path->dentry);

error = -EEXIST;
@@ -2423,8 +2448,6 @@ out:
terminate_walk(nd);
return filp;

-exit_mutex_unlock:
- mutex_unlock(&dir->d_inode->i_mutex);
exit_dput:
path_put_conditional(path, nd);
exit:
--
1.7.7


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