diff options
author | Dan Williams <dan.j.williams@intel.com> | 2021-04-01 16:33:19 +0200 |
---|---|---|
committer | Dan Williams <dan.j.williams@intel.com> | 2021-04-06 20:41:30 +0200 |
commit | 5877515912cc4f0d67071b7cee15076ebef24708 (patch) | |
tree | 26d67ea57a15e33606c0a064f76b6f0f6ca51caf /drivers/cxl | |
parent | cxl/mem: Use sysfs_emit() for attribute show routines (diff) | |
download | linux-5877515912cc4f0d67071b7cee15076ebef24708.tar.xz linux-5877515912cc4f0d67071b7cee15076ebef24708.zip |
cxl/mem: Fix synchronization mechanism for device removal vs ioctl operations
The percpu_ref to gate whether cxl_memdev_ioctl() is free to use the
driver context (@cxlm) to issue I/O is overkill, implemented incorrectly
(missing a device reference before accessing the percpu_ref), and the
complexities of shutting down a percpu_ref contributed to a bug in the
error unwind in cxl_mem_add_memdev() (missing put_device() to be fixed
separately).
Use an rwsem to explicitly synchronize the usage of cxlmd->cxlm, and add
the missing reference counting for cxlmd in cxl_memdev_open() and
cxl_memdev_release_file().
Fixes: b39cb1052a5c ("cxl/mem: Register CXL memX devices")
Reported-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/161728759948.2474381.17481500816783671817.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/cxl')
-rw-r--r-- | drivers/cxl/mem.c | 97 |
1 files changed, 50 insertions, 47 deletions
diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c index 832582033683..438f0861c46c 100644 --- a/drivers/cxl/mem.c +++ b/drivers/cxl/mem.c @@ -96,21 +96,18 @@ struct mbox_cmd { * @dev: driver core device object * @cdev: char dev core object for ioctl operations * @cxlm: pointer to the parent device driver data - * @ops_active: active user of @cxlm in ops handlers - * @ops_dead: completion when all @cxlm ops users have exited * @id: id number of this memdev instance. */ struct cxl_memdev { struct device dev; struct cdev cdev; struct cxl_mem *cxlm; - struct percpu_ref ops_active; - struct completion ops_dead; int id; }; static int cxl_mem_major; static DEFINE_IDA(cxl_memdev_ida); +static DECLARE_RWSEM(cxl_memdev_rwsem); static struct dentry *cxl_debugfs; static bool cxl_raw_allow_all; @@ -776,26 +773,43 @@ static long __cxl_memdev_ioctl(struct cxl_memdev *cxlmd, unsigned int cmd, static long cxl_memdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { - struct cxl_memdev *cxlmd; - struct inode *inode; - int rc = -ENOTTY; + struct cxl_memdev *cxlmd = file->private_data; + int rc = -ENXIO; - inode = file_inode(file); - cxlmd = container_of(inode->i_cdev, typeof(*cxlmd), cdev); + down_read(&cxl_memdev_rwsem); + if (cxlmd->cxlm) + rc = __cxl_memdev_ioctl(cxlmd, cmd, arg); + up_read(&cxl_memdev_rwsem); - if (!percpu_ref_tryget_live(&cxlmd->ops_active)) - return -ENXIO; + return rc; +} - rc = __cxl_memdev_ioctl(cxlmd, cmd, arg); +static int cxl_memdev_open(struct inode *inode, struct file *file) +{ + struct cxl_memdev *cxlmd = + container_of(inode->i_cdev, typeof(*cxlmd), cdev); - percpu_ref_put(&cxlmd->ops_active); + get_device(&cxlmd->dev); + file->private_data = cxlmd; - return rc; + return 0; +} + +static int cxl_memdev_release_file(struct inode *inode, struct file *file) +{ + struct cxl_memdev *cxlmd = + container_of(inode->i_cdev, typeof(*cxlmd), cdev); + + put_device(&cxlmd->dev); + + return 0; } static const struct file_operations cxl_memdev_fops = { .owner = THIS_MODULE, .unlocked_ioctl = cxl_memdev_ioctl, + .open = cxl_memdev_open, + .release = cxl_memdev_release_file, .compat_ioctl = compat_ptr_ioctl, .llseek = noop_llseek, }; @@ -1049,7 +1063,6 @@ static void cxl_memdev_release(struct device *dev) { struct cxl_memdev *cxlmd = to_cxl_memdev(dev); - percpu_ref_exit(&cxlmd->ops_active); ida_free(&cxl_memdev_ida, cxlmd->id); kfree(cxlmd); } @@ -1150,24 +1163,21 @@ static const struct device_type cxl_memdev_type = { .groups = cxl_memdev_attribute_groups, }; -static void cxlmdev_unregister(void *_cxlmd) +static void cxl_memdev_shutdown(struct cxl_memdev *cxlmd) { - struct cxl_memdev *cxlmd = _cxlmd; - struct device *dev = &cxlmd->dev; - - percpu_ref_kill(&cxlmd->ops_active); - cdev_device_del(&cxlmd->cdev, dev); - wait_for_completion(&cxlmd->ops_dead); + down_write(&cxl_memdev_rwsem); cxlmd->cxlm = NULL; - put_device(dev); + up_write(&cxl_memdev_rwsem); } -static void cxlmdev_ops_active_release(struct percpu_ref *ref) +static void cxl_memdev_unregister(void *_cxlmd) { - struct cxl_memdev *cxlmd = - container_of(ref, typeof(*cxlmd), ops_active); + struct cxl_memdev *cxlmd = _cxlmd; + struct device *dev = &cxlmd->dev; - complete(&cxlmd->ops_dead); + cdev_device_del(&cxlmd->cdev, dev); + cxl_memdev_shutdown(cxlmd); + put_device(dev); } static int cxl_mem_add_memdev(struct cxl_mem *cxlm) @@ -1181,17 +1191,6 @@ static int cxl_mem_add_memdev(struct cxl_mem *cxlm) cxlmd = kzalloc(sizeof(*cxlmd), GFP_KERNEL); if (!cxlmd) return -ENOMEM; - init_completion(&cxlmd->ops_dead); - - /* - * @cxlm is deallocated when the driver unbinds so operations - * that are using it need to hold a live reference. - */ - cxlmd->cxlm = cxlm; - rc = percpu_ref_init(&cxlmd->ops_active, cxlmdev_ops_active_release, 0, - GFP_KERNEL); - if (rc) - goto err_ref; rc = ida_alloc_range(&cxl_memdev_ida, 0, CXL_MEM_MAX_DEVS, GFP_KERNEL); if (rc < 0) @@ -1209,23 +1208,27 @@ static int cxl_mem_add_memdev(struct cxl_mem *cxlm) cdev = &cxlmd->cdev; cdev_init(cdev, &cxl_memdev_fops); + /* + * Activate ioctl operations, no cxl_memdev_rwsem manipulation + * needed as this is ordered with cdev_add() publishing the device. + */ + cxlmd->cxlm = cxlm; + rc = cdev_device_add(cdev, dev); if (rc) goto err_add; - return devm_add_action_or_reset(dev->parent, cxlmdev_unregister, cxlmd); + return devm_add_action_or_reset(dev->parent, cxl_memdev_unregister, + cxlmd); err_add: - ida_free(&cxl_memdev_ida, cxlmd->id); -err_id: /* - * Theoretically userspace could have already entered the fops, - * so flush ops_active. + * The cdev was briefly live, shutdown any ioctl operations that + * saw that state. */ - percpu_ref_kill(&cxlmd->ops_active); - wait_for_completion(&cxlmd->ops_dead); - percpu_ref_exit(&cxlmd->ops_active); -err_ref: + cxl_memdev_shutdown(cxlmd); + ida_free(&cxl_memdev_ida, cxlmd->id); +err_id: kfree(cxlmd); return rc; |