diff options
Diffstat (limited to 'fs/debugfs/file.c')
| -rw-r--r-- | fs/debugfs/file.c | 55 |
1 files changed, 46 insertions, 9 deletions
diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c index bc3549c95574..65872340e301 100644 --- a/fs/debugfs/file.c +++ b/fs/debugfs/file.c @@ -53,6 +53,15 @@ const struct file_operations *debugfs_real_fops(const struct file *filp) { struct debugfs_fsdata *fsd = F_DENTRY(filp)->d_fsdata; + if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT) { + /* + * Urgh, we've been called w/o a protecting + * debugfs_file_get(). + */ + WARN_ON(1); + return NULL; + } + return fsd->real_fops; } EXPORT_SYMBOL_GPL(debugfs_real_fops); @@ -74,9 +83,35 @@ EXPORT_SYMBOL_GPL(debugfs_real_fops); */ int debugfs_file_get(struct dentry *dentry) { - struct debugfs_fsdata *fsd = dentry->d_fsdata; + struct debugfs_fsdata *fsd; + void *d_fsd; + + d_fsd = READ_ONCE(dentry->d_fsdata); + if (!((unsigned long)d_fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)) { + fsd = d_fsd; + } else { + fsd = kmalloc(sizeof(*fsd), GFP_KERNEL); + if (!fsd) + return -ENOMEM; + + fsd->real_fops = (void *)((unsigned long)d_fsd & + ~DEBUGFS_FSDATA_IS_REAL_FOPS_BIT); + refcount_set(&fsd->active_users, 1); + init_completion(&fsd->active_users_drained); + if (cmpxchg(&dentry->d_fsdata, d_fsd, fsd) != d_fsd) { + kfree(fsd); + fsd = READ_ONCE(dentry->d_fsdata); + } + } - /* Avoid starvation of removers. */ + /* + * In case of a successful cmpxchg() above, this check is + * strictly necessary and must follow it, see the comment in + * __debugfs_remove_file(). + * OTOH, if the cmpxchg() hasn't been executed or wasn't + * successful, this serves the purpose of not starving + * removers. + */ if (d_unlinked(dentry)) return -EIO; @@ -98,7 +133,7 @@ EXPORT_SYMBOL_GPL(debugfs_file_get); */ void debugfs_file_put(struct dentry *dentry) { - struct debugfs_fsdata *fsd = dentry->d_fsdata; + struct debugfs_fsdata *fsd = READ_ONCE(dentry->d_fsdata); if (refcount_dec_and_test(&fsd->active_users)) complete(&fsd->active_users_drained); @@ -109,10 +144,11 @@ static int open_proxy_open(struct inode *inode, struct file *filp) { struct dentry *dentry = F_DENTRY(filp); const struct file_operations *real_fops = NULL; - int r = 0; + int r; - if (debugfs_file_get(dentry)) - return -ENOENT; + r = debugfs_file_get(dentry); + if (r) + return r == -EIO ? -ENOENT : r; real_fops = debugfs_real_fops(filp); real_fops = fops_get(real_fops); @@ -233,10 +269,11 @@ static int full_proxy_open(struct inode *inode, struct file *filp) struct dentry *dentry = F_DENTRY(filp); const struct file_operations *real_fops = NULL; struct file_operations *proxy_fops = NULL; - int r = 0; + int r; - if (debugfs_file_get(dentry)) - return -ENOENT; + r = debugfs_file_get(dentry); + if (r) + return r == -EIO ? -ENOENT : r; real_fops = debugfs_real_fops(filp); real_fops = fops_get(real_fops); |