Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756053AbdDPJxp (ORCPT ); Sun, 16 Apr 2017 05:53:45 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:33640 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754927AbdDPJvt (ORCPT ); Sun, 16 Apr 2017 05:51:49 -0400 From: Nicolai Stange To: Greg Kroah-Hartman Cc: Johannes Berg , "Paul E.McKenney" , Nicolai Stange , linux-kernel@vger.kernel.org Subject: [RFC PATCH 1/9] debugfs: add support for more elaborate ->d_fsdata Date: Sun, 16 Apr 2017 11:51:29 +0200 Message-Id: <20170416095137.2784-2-nicstange@gmail.com> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170416095137.2784-1-nicstange@gmail.com> References: <871stdyg0u.fsf@gmail.com> <20170416095137.2784-1-nicstange@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5029 Lines: 160 Currently, the user provided fops, "real_fops", are stored directly into ->d_fsdata. In order to be able to store more per-file state and thus prepare for more granular file removal protection, wrap the real_fops into a dynamically allocated container struct, debugfs_fsdata. A struct debugfs_fsdata gets allocated at file creation and freed from the newly intoduced ->d_release(). Finally, move the implementation of debugfs_real_fops() out of the public debugfs header such that struct debugfs_fsdata's declaration can be kept private. Signed-off-by: Nicolai Stange --- fs/debugfs/file.c | 12 ++++++++++++ fs/debugfs/inode.c | 22 +++++++++++++++++++--- fs/debugfs/internal.h | 4 ++++ include/linux/debugfs.h | 20 +++----------------- 4 files changed, 38 insertions(+), 20 deletions(-) diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c index 354e2ab62031..15655a1a0704 100644 --- a/fs/debugfs/file.c +++ b/fs/debugfs/file.c @@ -97,6 +97,18 @@ EXPORT_SYMBOL_GPL(debugfs_use_file_finish); #define F_DENTRY(filp) ((filp)->f_path.dentry) +const struct file_operations *debugfs_real_fops(const struct file *filp) + __must_hold(&debugfs_srcu) +{ + struct debugfs_fsdata *fsd = F_DENTRY(filp)->d_fsdata; + /* + * Neither the pointer to the struct file_operations, nor its + * contents ever change -- srcu_dereference() is not needed here. + */ + return fsd->real_fops; +} +EXPORT_SYMBOL_GPL(debugfs_real_fops); + static int open_proxy_open(struct inode *inode, struct file *filp) { const struct dentry *dentry = F_DENTRY(filp); diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c index 7fd4ec4bb214..1ae133064ca1 100644 --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -185,6 +185,11 @@ static const struct super_operations debugfs_super_operations = { .evict_inode = debugfs_evict_inode, }; +static void debugfs_release_dentry(struct dentry *dentry) +{ + kfree(dentry->d_fsdata); +} + static struct vfsmount *debugfs_automount(struct path *path) { debugfs_automount_t f; @@ -194,6 +199,7 @@ static struct vfsmount *debugfs_automount(struct path *path) static const struct dentry_operations debugfs_dops = { .d_delete = always_delete_dentry, + .d_release = debugfs_release_dentry, .d_automount = debugfs_automount, }; @@ -343,24 +349,34 @@ static struct dentry *__debugfs_create_file(const char *name, umode_t mode, { struct dentry *dentry; struct inode *inode; + struct debugfs_fsdata *fsd; + + fsd = kmalloc(sizeof(*fsd), GFP_KERNEL); + if (!fsd) + return NULL; if (!(mode & S_IFMT)) mode |= S_IFREG; BUG_ON(!S_ISREG(mode)); dentry = start_creating(name, parent); - if (IS_ERR(dentry)) + if (IS_ERR(dentry)) { + kfree(fsd); return NULL; + } inode = debugfs_get_inode(dentry->d_sb); - if (unlikely(!inode)) + if (unlikely(!inode)) { + kfree(fsd); return failed_creating(dentry); + } inode->i_mode = mode; inode->i_private = data; inode->i_fop = proxy_fops; - dentry->d_fsdata = (void *)real_fops; + fsd->real_fops = real_fops; + dentry->d_fsdata = fsd; d_instantiate(dentry, inode); fsnotify_create(d_inode(dentry->d_parent), dentry); diff --git a/fs/debugfs/internal.h b/fs/debugfs/internal.h index b3e8443a1f47..512601eed3ce 100644 --- a/fs/debugfs/internal.h +++ b/fs/debugfs/internal.h @@ -19,4 +19,8 @@ extern const struct file_operations debugfs_noop_file_operations; extern const struct file_operations debugfs_open_proxy_file_operations; extern const struct file_operations debugfs_full_proxy_file_operations; +struct debugfs_fsdata { + const struct file_operations *real_fops; +}; + #endif /* _DEBUGFS_INTERNAL_H_ */ diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h index 9174b0d28582..d614be21412a 100644 --- a/include/linux/debugfs.h +++ b/include/linux/debugfs.h @@ -45,23 +45,6 @@ extern struct dentry *arch_debugfs_dir; extern struct srcu_struct debugfs_srcu; -/** - * debugfs_real_fops - getter for the real file operation - * @filp: a pointer to a struct file - * - * Must only be called under the protection established by - * debugfs_use_file_start(). - */ -static inline const struct file_operations *debugfs_real_fops(const struct file *filp) - __must_hold(&debugfs_srcu) -{ - /* - * Neither the pointer to the struct file_operations, nor its - * contents ever change -- srcu_dereference() is not needed here. - */ - return filp->f_path.dentry->d_fsdata; -} - #define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt) \ static int __fops ## _open(struct inode *inode, struct file *file) \ { \ @@ -112,6 +95,9 @@ int debugfs_use_file_start(const struct dentry *dentry, int *srcu_idx) void debugfs_use_file_finish(int srcu_idx) __releases(&debugfs_srcu); +const struct file_operations *debugfs_real_fops(const struct file *filp) + __must_hold(&debugfs_srcu); + ssize_t debugfs_attr_read(struct file *file, char __user *buf, size_t len, loff_t *ppos); ssize_t debugfs_attr_write(struct file *file, const char __user *buf, -- 2.12.2