vfs: add i_op->atomic_open() (d18e9008) · Commits · 戴 / test

Documentation/filesystems/Locking

+4 −0

Original line number	Diff line number	Diff line
		@@ -62,6 +62,9 @@ ata *);
		int (removexattr) (struct dentry , const char *);
		int (fiemap)(struct inode , struct fiemap_extent_info *, u64 start, u64 len);
		void (update_time)(struct inode , struct timespec *, int);
		struct file * (atomic_open)(struct inode , struct dentry *,
		struct opendata *, unsigned open_flag,
		umode_t create_mode, bool *created);

		locking rules:
		all may block
		@@ -89,6 +92,7 @@ listxattr: no
		removexattr: yes
		fiemap: no
		update_time: no
		atomic_open: yes

		Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
		victim.

Documentation/filesystems/vfs.txt

+11 −0

Original line number	Diff line number	Diff line
		@@ -364,6 +364,9 @@ struct inode_operations {
		ssize_t (listxattr) (struct dentry , char *, size_t);
		int (removexattr) (struct dentry , const char *);
		void (update_time)(struct inode , struct timespec *, int);
		struct file * (atomic_open)(struct inode , struct dentry *,
		struct opendata *, unsigned open_flag,
		umode_t create_mode, bool *created);
		};

		Again, all methods are called without any locks being held, unless
		@@ -476,6 +479,14 @@ otherwise noted.
		an inode. If this is not defined the VFS will update the inode itself
		and call mark_inode_dirty_sync.

		atomic_open: called on the last component of an open. Using this optional
		method the filesystem can look up, possibly create and open the file in
		one atomic operation. If it cannot perform this (e.g. the file type
		turned out to be wrong) it may signal this by returning NULL instead of
		an open struct file pointer. This method is only called if the last
		component is negative or needs lookup. Cached positive dentries are
		still handled by f_op->open().

		The Address Space Object
		========================

fs/internal.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -85,6 +85,11 @@ extern struct super_block *user_get_super(dev_t);
		struct nameidata;
		extern struct file nameidata_to_filp(struct nameidata );
		extern void release_open_intent(struct nameidata *);
		struct opendata {
		struct dentry *dentry;
		struct vfsmount *mnt;
		struct file **filp;
		};
		struct open_flags {
		int open_flag;
		umode_t mode;

fs/namei.c

+201 −2

Original line number	Diff line number	Diff line
		@@ -2196,6 +2196,176 @@ static inline int open_to_namei_flags(int flag)
		return flag;
		}

		static int may_o_create(struct path dir, struct dentry dentry, umode_t mode)
		{
		int error = security_path_mknod(dir, dentry, mode, 0);
		if (error)
		return error;

		error = inode_permission(dir->dentry->d_inode, MAY_WRITE \| MAY_EXEC);
		if (error)
		return error;

		return security_inode_create(dir->dentry->d_inode, dentry, mode);
		}

		static struct file atomic_open(struct nameidata nd, struct dentry *dentry,
		struct path path, const struct open_flags op,
		int *want_write, bool need_lookup,
		bool *created)
		{
		struct inode *dir = nd->path.dentry->d_inode;
		unsigned open_flag = open_to_namei_flags(op->open_flag);
		umode_t mode;
		int error;
		int acc_mode;
		struct opendata od;
		struct file *filp;
		int create_error = 0;
		struct dentry const DENTRY_NOT_SET = (void ) -1UL;

		BUG_ON(dentry->d_inode);

		/* Don't create child dentry for a dead directory. */
		if (unlikely(IS_DEADDIR(dir))) {
		filp = ERR_PTR(-ENOENT);
		goto out;
		}

		mode = op->mode & S_IALLUGO;
		if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
		mode &= ~current_umask();

		if (open_flag & O_EXCL) {
		open_flag &= ~O_TRUNC;
		*created = true;
		}

		/*
		* Checking write permission is tricky, bacuse we don't know if we are
		* going to actually need it: O_CREAT opens should work as long as the
		* file exists. But checking existence breaks atomicity. The trick is
		* to check access and if not granted clear O_CREAT from the flags.
		*
		* Another problem is returing the "right" error value (e.g. for an
		* O_EXCL open we want to return EEXIST not EROFS).
		*/
		if ((open_flag & (O_CREAT \| O_TRUNC)) \|\|
		(open_flag & O_ACCMODE) != O_RDONLY) {
		error = mnt_want_write(nd->path.mnt);
		if (!error) {
		*want_write = 1;
		} else if (!(open_flag & O_CREAT)) {
		/*
		* No O_CREATE -> atomicity not a requirement -> fall
		* back to lookup + open
		*/
		goto no_open;
		} else if (open_flag & (O_EXCL \| O_TRUNC)) {
		/* Fall back and fail with the right error */
		create_error = error;
		goto no_open;
		} else {
		/* No side effects, safe to clear O_CREAT */
		create_error = error;
		open_flag &= ~O_CREAT;
		}
		}

		if (open_flag & O_CREAT) {
		error = may_o_create(&nd->path, dentry, op->mode);
		if (error) {
		create_error = error;
		if (open_flag & O_EXCL)
		goto no_open;
		open_flag &= ~O_CREAT;
		}
		}

		if (nd->flags & LOOKUP_DIRECTORY)
		open_flag \|= O_DIRECTORY;

		od.dentry = DENTRY_NOT_SET;
		od.mnt = nd->path.mnt;
		od.filp = &nd->intent.open.file;
		filp = dir->i_op->atomic_open(dir, dentry, &od, open_flag, mode,
		created);
		if (IS_ERR(filp)) {
		if (WARN_ON(od.dentry != DENTRY_NOT_SET))
		dput(od.dentry);

		if (create_error && PTR_ERR(filp) == -ENOENT)
		filp = ERR_PTR(create_error);
		goto out;
		}

		acc_mode = op->acc_mode;
		if (*created) {
		fsnotify_create(dir, dentry);
		acc_mode = MAY_OPEN;
		}

		if (!filp) {
		if (WARN_ON(od.dentry == DENTRY_NOT_SET)) {
		filp = ERR_PTR(-EIO);
		goto out;
		}
		if (od.dentry) {
		dput(dentry);
		dentry = od.dentry;
		}
		goto looked_up;
		}

		/*
		* We didn't have the inode before the open, so check open permission
		* here.
		*/
		error = may_open(&filp->f_path, acc_mode, open_flag);
		if (error)
		goto out_fput;

		error = open_check_o_direct(filp);
		if (error)
		goto out_fput;

		out:
		dput(dentry);
		return filp;

		out_fput:
		fput(filp);
		filp = ERR_PTR(error);
		goto out;

		no_open:
		if (need_lookup) {
		dentry = lookup_real(dir, dentry, nd);
		if (IS_ERR(dentry))
		return ERR_CAST(dentry);

		if (create_error) {
		int open_flag = op->open_flag;

		filp = ERR_PTR(create_error);
		if ((open_flag & O_EXCL)) {
		if (!dentry->d_inode)
		goto out;
		} else if (!dentry->d_inode) {
		goto out;
		} else if ((open_flag & O_TRUNC) &&
		S_ISREG(dentry->d_inode->i_mode)) {
		goto out;
		}
		/* will fail later, go on to get the right error */
		}
		}
		looked_up:
		path->dentry = dentry;
		path->mnt = nd->path.mnt;
		return NULL;
		}

		/*
		* Lookup, maybe create and open the last component
		*
		@@ -2219,6 +2389,15 @@ static struct file lookup_open(struct nameidata nd, struct path *path,
		if (IS_ERR(dentry))
		return ERR_CAST(dentry);

		/* Cached positive dentry: will open in f_op->open */
		if (!need_lookup && dentry->d_inode)
		goto out_no_open;

		if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
		return atomic_open(nd, dentry, path, op, want_write,
		need_lookup, created);
		}

		if (need_lookup) {
		BUG_ON(dentry->d_inode);

		@@ -2251,6 +2430,7 @@ static struct file lookup_open(struct nameidata nd, struct path *path,
		if (error)
		goto out_dput;
		}
		out_no_open:
		path->dentry = dentry;
		path->mnt = nd->path.mnt;
		return NULL;
		@@ -2344,9 +2524,17 @@ retry_lookup:
		filp = lookup_open(nd, path, op, &want_write, &created);
		mutex_unlock(&dir->d_inode->i_mutex);

		if (filp) {
		if (IS_ERR(filp))
		goto out;

		if (created \|\| !S_ISREG(filp->f_path.dentry->d_inode->i_mode))
		will_truncate = 0;

		audit_inode(pathname, filp->f_path.dentry);
		goto opened;
		}

		if (created) {
		/* Don't check for write permission, don't truncate */
		open_flag &= ~O_TRUNC;
		@@ -2361,6 +2549,16 @@ retry_lookup:
		*/
		audit_inode(pathname, path->dentry);

		/*
		* If atomic_open() acquired write access it is dropped now due to
		* possible mount and symlink following (this might be optimized away if
		* necessary...)
		*/
		if (want_write) {
		mnt_drop_write(nd->path.mnt);
		want_write = 0;
		}

		error = -EEXIST;
		if (open_flag & O_EXCL)
		goto exit_dput;
		@@ -2444,6 +2642,7 @@ common:
		retried = true;
		goto retry_lookup;
		}
		opened:
		if (!IS_ERR(filp)) {
		error = ima_file_check(filp, op->acc_mode);
		if (error) {

fs/open.c

+42 −0

Original line number	Diff line number	Diff line
		@@ -810,6 +810,48 @@ out_err:
		}
		EXPORT_SYMBOL_GPL(lookup_instantiate_filp);

		/**
		* finish_open - finish opening a file
		* @od: opaque open data
		* @dentry: pointer to dentry
		* @open: open callback
		*
		* This can be used to finish opening a file passed to i_op->atomic_open().
		*
		* If the open callback is set to NULL, then the standard f_op->open()
		* filesystem callback is substituted.
		*/
		struct file finish_open(struct opendata od, struct dentry *dentry,
		int (open)(struct inode , struct file *))
		{
		struct file *res;

		mntget(od->mnt);
		dget(dentry);

		res = do_dentry_open(dentry, od->mnt, *od->filp, open, current_cred());
		if (!IS_ERR(res))
		*od->filp = NULL;

		return res;
		}
		EXPORT_SYMBOL(finish_open);

		/**
		* finish_no_open - finish ->atomic_open() without opening the file
		*
		* @od: opaque open data
		* @dentry: dentry or NULL (as returned from ->lookup())
		*
		* This can be used to set the result of a successful lookup in ->atomic_open().
		* The filesystem's atomic_open() method shall return NULL after calling this.
		*/
		void finish_no_open(struct opendata od, struct dentry dentry)
		{
		od->dentry = dentry;
		}
		EXPORT_SYMBOL(finish_no_open);

		/**
		* nameidata_to_filp - convert a nameidata to an open filp.
		* @nd: pointer to nameidata

Admin message