diff options
Diffstat (limited to 'fs/debugfs')
| -rw-r--r-- | fs/debugfs/file.c | 91 | ||||
| -rw-r--r-- | fs/debugfs/inode.c | 13 | ||||
| -rw-r--r-- | fs/debugfs/internal.h | 24 |
3 files changed, 126 insertions, 2 deletions
diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c index d2ba12e23ed9..736ab3c988f2 100644 --- a/fs/debugfs/file.c +++ b/fs/debugfs/file.c @@ -22,6 +22,9 @@ #include <linux/slab.h> #include <linux/atomic.h> #include <linux/device.h> +#include <linux/srcu.h> + +#include "internal.h" static ssize_t default_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) @@ -35,13 +38,99 @@ static ssize_t default_write_file(struct file *file, const char __user *buf, return count; } -const struct file_operations debugfs_file_operations = { +const struct file_operations debugfs_noop_file_operations = { .read = default_read_file, .write = default_write_file, .open = simple_open, .llseek = noop_llseek, }; +/** + * debugfs_use_file_start - mark the beginning of file data access + * @dentry: the dentry object whose data is being accessed. + * @srcu_idx: a pointer to some memory to store a SRCU index in. + * + * Up to a matching call to debugfs_use_file_finish(), any + * successive call into the file removing functions debugfs_remove() + * and debugfs_remove_recursive() will block. Since associated private + * file data may only get freed after a successful return of any of + * the removal functions, you may safely access it after a successful + * call to debugfs_use_file_start() without worrying about + * lifetime issues. + * + * If -%EIO is returned, the file has already been removed and thus, + * it is not safe to access any of its data. If, on the other hand, + * it is allowed to access the file data, zero is returned. + * + * Regardless of the return code, any call to + * debugfs_use_file_start() must be followed by a matching call + * to debugfs_use_file_finish(). + */ +static int debugfs_use_file_start(const struct dentry *dentry, int *srcu_idx) + __acquires(&debugfs_srcu) +{ + *srcu_idx = srcu_read_lock(&debugfs_srcu); + barrier(); + if (d_unlinked(dentry)) + return -EIO; + return 0; +} + +/** + * debugfs_use_file_finish - mark the end of file data access + * @srcu_idx: the SRCU index "created" by a former call to + * debugfs_use_file_start(). + * + * Allow any ongoing concurrent call into debugfs_remove() or + * debugfs_remove_recursive() blocked by a former call to + * debugfs_use_file_start() to proceed and return to its caller. + */ +static void debugfs_use_file_finish(int srcu_idx) __releases(&debugfs_srcu) +{ + srcu_read_unlock(&debugfs_srcu, srcu_idx); +} + +#define F_DENTRY(filp) ((filp)->f_path.dentry) + +#define REAL_FOPS_DEREF(dentry) \ + ((const struct file_operations *)(dentry)->d_fsdata) + +static int open_proxy_open(struct inode *inode, struct file *filp) +{ + const struct dentry *dentry = F_DENTRY(filp); + const struct file_operations *real_fops = NULL; + int srcu_idx, r; + + r = debugfs_use_file_start(dentry, &srcu_idx); + if (r) { + r = -ENOENT; + goto out; + } + + real_fops = REAL_FOPS_DEREF(dentry); + real_fops = fops_get(real_fops); + if (!real_fops) { + /* Huh? Module did not clean up after itself at exit? */ + WARN(1, "debugfs file owner did not clean up at exit: %pd", + dentry); + r = -ENXIO; + goto out; + } + replace_fops(filp, real_fops); + + if (real_fops->open) + r = real_fops->open(inode, filp); + +out: + fops_put(real_fops); + debugfs_use_file_finish(srcu_idx); + return r; +} + +const struct file_operations debugfs_open_proxy_file_operations = { + .open = open_proxy_open, +}; + static struct dentry *debugfs_create_mode(const char *name, umode_t mode, struct dentry *parent, void *value, const struct file_operations *fops, diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c index b1e7f35f3cd4..2905dd160575 100644 --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -27,9 +27,14 @@ #include <linux/parser.h> #include <linux/magic.h> #include <linux/slab.h> +#include <linux/srcu.h> + +#include "internal.h" #define DEBUGFS_DEFAULT_MODE 0700 +DEFINE_SRCU(debugfs_srcu); + static struct vfsmount *debugfs_mount; static int debugfs_mount_count; static bool debugfs_registered; @@ -341,8 +346,12 @@ struct dentry *debugfs_create_file(const char *name, umode_t mode, return failed_creating(dentry); inode->i_mode = mode; - inode->i_fop = fops ? fops : &debugfs_file_operations; inode->i_private = data; + + inode->i_fop = fops ? &debugfs_open_proxy_file_operations + : &debugfs_noop_file_operations; + dentry->d_fsdata = (void *)fops; + d_instantiate(dentry, inode); fsnotify_create(d_inode(dentry->d_parent), dentry); return end_creating(dentry); @@ -570,6 +579,7 @@ void debugfs_remove(struct dentry *dentry) inode_unlock(d_inode(parent)); if (!ret) simple_release_fs(&debugfs_mount, &debugfs_mount_count); + synchronize_srcu(&debugfs_srcu); } EXPORT_SYMBOL_GPL(debugfs_remove); @@ -647,6 +657,7 @@ void debugfs_remove_recursive(struct dentry *dentry) if (!__debugfs_remove(child, parent)) simple_release_fs(&debugfs_mount, &debugfs_mount_count); inode_unlock(d_inode(parent)); + synchronize_srcu(&debugfs_srcu); } EXPORT_SYMBOL_GPL(debugfs_remove_recursive); diff --git a/fs/debugfs/internal.h b/fs/debugfs/internal.h new file mode 100644 index 000000000000..c7aaa5cb6685 --- /dev/null +++ b/fs/debugfs/internal.h @@ -0,0 +1,24 @@ +/* + * internal.h - declarations internal to debugfs + * + * Copyright (C) 2016 Nicolai Stange <nicstange@gmail.com> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License version + * 2 as published by the Free Software Foundation. + * + */ + +#ifndef _DEBUGFS_INTERNAL_H_ +#define _DEBUGFS_INTERNAL_H_ + +struct file_operations; +struct srcu_struct; + +/* declared over in file.c */ +extern const struct file_operations debugfs_noop_file_operations; +extern const struct file_operations debugfs_open_proxy_file_operations; + +extern struct srcu_struct debugfs_srcu; + +#endif /* _DEBUGFS_INTERNAL_H_ */ |