On Wed, Oct 07, 2020 at 12:13:27AM -0700, Kees Cook wrote:
> On Tue, Oct 06, 2020 at 05:52:20PM +0200, Christoph Hellwig wrote:
> > Hi WeiXiong, hi Kees,
> >
> > what is the use case for the code added in commit 17639f67c1d6
> > ("pstore/blk: Introduce backend for block devices").
> >
> > This still doesn't have a user, and the API looks really odd to me.
>
> pstore is a beast. :) The API is there so that a blk device can declare
> its direct support of pstore (specifically, to provide a panic_write
> handler).
>
> The MTD device does this, but yes, that's a good point, there isn't a
> blk device user of that entry point yet.
>
> > By our normal kernel rules we should not add new exports without
> > users and this should probably be reverted for the 5.9 release.
>
> I don't want to revert the entire patch (I'm still using
> __register_pstore_blk by way of pstore/blk's "best_effort" option), but
> I wouldn't object to something like this:
FYI, I'd be much happier with this, which removes the crazy block
device autoprobe, and the completely broken block device read/write
path as well:
diff --git a/Documentation/admin-guide/pstore-blk.rst
b/Documentation/admin-guide/pstore-blk.rst
index 296d5027787ac2..84d15c53d094c0 100644
--- a/Documentation/admin-guide/pstore-blk.rst
+++ b/Documentation/admin-guide/pstore-blk.rst
@@ -151,13 +151,7 @@ otherwise KMSG_DUMP_MAX.
Configurations for driver
-------------------------
-Only a block device driver cares about these configurations. A block device
-driver uses ``register_pstore_blk`` to register to pstore/blk.
-
-.. kernel-doc:: fs/pstore/blk.c
- :identifiers: register_pstore_blk
-
-A non-block device driver uses ``register_pstore_device`` with
+Device drivers use ``register_pstore_device`` with
``struct pstore_device_info`` to register to pstore/blk.
.. kernel-doc:: fs/pstore/blk.c
diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
index fcd5563dde063c..3a8224c6df24f5 100644
--- a/fs/pstore/blk.c
+++ b/fs/pstore/blk.c
@@ -88,15 +88,7 @@ MODULE_PARM_DESC(blkdev, "block device for pstore storage");
* during the register/unregister functions.
*/
static DEFINE_MUTEX(pstore_blk_lock);
-static struct block_device *psblk_bdev;
static struct pstore_zone_info *pstore_zone_info;
-static pstore_blk_panic_write_op blkdev_panic_write;
-
-struct bdev_info {
- dev_t devt;
- sector_t nr_sects;
- sector_t start_sect;
-};
#define check_size(name, alignsize) ({ \
long _##name_ = (name); \
@@ -206,267 +198,6 @@ void unregister_pstore_device(struct pstore_device_info
*dev)
}
EXPORT_SYMBOL_GPL(unregister_pstore_device);
-/**
- * psblk_get_bdev() - open block device
- *
- * @holder: Exclusive holder identifier
- * @info: Information about bdev to fill in
- *
- * Return: pointer to block device on success and others on error.
- *
- * On success, the returned block_device has reference count of one.
- */
-static struct block_device *psblk_get_bdev(void *holder,
- struct bdev_info *info)
-{
- struct block_device *bdev = ERR_PTR(-ENODEV);
- fmode_t mode = FMODE_READ | FMODE_WRITE;
- sector_t nr_sects;
-
- lockdep_assert_held(&pstore_blk_lock);
-
- if (pstore_zone_info)
- return ERR_PTR(-EBUSY);
-
- if (!blkdev[0])
- return ERR_PTR(-ENODEV);
-
- if (holder)
- mode |= FMODE_EXCL;
- bdev = blkdev_get_by_path(blkdev, mode, holder);
- if (IS_ERR(bdev)) {
- dev_t devt;
-
- devt = name_to_dev_t(blkdev);
- if (devt == 0)
- return ERR_PTR(-ENODEV);
- bdev = blkdev_get_by_dev(devt, mode, holder);
- if (IS_ERR(bdev))
- return bdev;
- }
-
- nr_sects = part_nr_sects_read(bdev->bd_part);
- if (!nr_sects) {
- pr_err("not enough space for '%s'\n", blkdev);
- blkdev_put(bdev, mode);
- return ERR_PTR(-ENOSPC);
- }
-
- if (info) {
- info->devt = bdev->bd_dev;
- info->nr_sects = nr_sects;
- info->start_sect = get_start_sect(bdev);
- }
-
- return bdev;
-}
-
-static void psblk_put_bdev(struct block_device *bdev, void *holder)
-{
- fmode_t mode = FMODE_READ | FMODE_WRITE;
-
- lockdep_assert_held(&pstore_blk_lock);
-
- if (!bdev)
- return;
-
- if (holder)
- mode |= FMODE_EXCL;
- blkdev_put(bdev, mode);
-}
-
-static ssize_t psblk_generic_blk_read(char *buf, size_t bytes, loff_t pos)
-{
- struct block_device *bdev = psblk_bdev;
- struct file file;
- struct kiocb kiocb;
- struct iov_iter iter;
- struct kvec iov = {.iov_base = buf, .iov_len = bytes};
-
- if (!bdev)
- return -ENODEV;
-
- memset(&file, 0, sizeof(struct file));
- file.f_mapping = bdev->bd_inode->i_mapping;
- file.f_flags = O_DSYNC | __O_SYNC | O_NOATIME;
- file.f_inode = bdev->bd_inode;
- file_ra_state_init(&file.f_ra, file.f_mapping);
-
- init_sync_kiocb(&kiocb, &file);
- kiocb.ki_pos = pos;
- iov_iter_kvec(&iter, READ, &iov, 1, bytes);
-
- return generic_file_read_iter(&kiocb, &iter);
-}
-
-static ssize_t psblk_generic_blk_write(const char *buf, size_t bytes,
- loff_t pos)
-{
- struct block_device *bdev = psblk_bdev;
- struct iov_iter iter;
- struct kiocb kiocb;
- struct file file;
- ssize_t ret;
- struct kvec iov = {.iov_base = (void *)buf, .iov_len = bytes};
-
- if (!bdev)
- return -ENODEV;
-
- /* Console/Ftrace backend may handle buffer until flush dirty zones */
- if (in_interrupt() || irqs_disabled())
- return -EBUSY;
-
- memset(&file, 0, sizeof(struct file));
- file.f_mapping = bdev->bd_inode->i_mapping;
- file.f_flags = O_DSYNC | __O_SYNC | O_NOATIME;
- file.f_inode = bdev->bd_inode;
-
- init_sync_kiocb(&kiocb, &file);
- kiocb.ki_pos = pos;
- iov_iter_kvec(&iter, WRITE, &iov, 1, bytes);
-
- inode_lock(bdev->bd_inode);
- ret = generic_write_checks(&kiocb, &iter);
- if (ret > 0)
- ret = generic_perform_write(&file, &iter, pos);
- inode_unlock(bdev->bd_inode);
-
- if (likely(ret > 0)) {
- const struct file_operations f_op = {.fsync = blkdev_fsync};
-
- file.f_op = &f_op;
- kiocb.ki_pos += ret;
- ret = generic_write_sync(&kiocb, ret);
- }
- return ret;
-}
-
-static ssize_t psblk_blk_panic_write(const char *buf, size_t size,
- loff_t off)
-{
- int ret;
-
- if (!blkdev_panic_write)
- return -EOPNOTSUPP;
-
- /* size and off must align to SECTOR_SIZE for block device */
- ret = blkdev_panic_write(buf, off >> SECTOR_SHIFT,
- size >> SECTOR_SHIFT);
- /* try next zone */
- if (ret == -ENOMSG)
- return ret;
- return ret ? -EIO : size;
-}
-
-static int __register_pstore_blk(struct pstore_blk_info *info)
-{
- char bdev_name[BDEVNAME_SIZE];
- struct block_device *bdev;
- struct pstore_device_info dev;
- struct bdev_info binfo;
- void *holder = blkdev;
- int ret = -ENODEV;
-
- lockdep_assert_held(&pstore_blk_lock);
-
- /* hold bdev exclusively */
- memset(&binfo, 0, sizeof(binfo));
- bdev = psblk_get_bdev(holder, &binfo);
- if (IS_ERR(bdev)) {
- pr_err("failed to open '%s'!\n", blkdev);
- return PTR_ERR(bdev);
- }
-
- /* only allow driver matching the @blkdev */
- if (!binfo.devt || (!best_effort &&
- MAJOR(binfo.devt) != info->major)) {
- pr_debug("invalid major %u (expect %u)\n",
- info->major, MAJOR(binfo.devt));
- ret = -ENODEV;
- goto err_put_bdev;
- }
-
- /* psblk_bdev must be assigned before register to pstore/blk */
- psblk_bdev = bdev;
- blkdev_panic_write = info->panic_write;
-
- /* Copy back block device details. */
- info->devt = binfo.devt;
- info->nr_sects = binfo.nr_sects;
- info->start_sect = binfo.start_sect;
-
- memset(&dev, 0, sizeof(dev));
- dev.total_size = info->nr_sects << SECTOR_SHIFT;
- dev.flags = info->flags;
- dev.read = psblk_generic_blk_read;
- dev.write = psblk_generic_blk_write;
- dev.erase = NULL;
- dev.panic_write = info->panic_write ? psblk_blk_panic_write : NULL;
-
- ret = __register_pstore_device(&dev);
- if (ret)
- goto err_put_bdev;
-
- bdevname(bdev, bdev_name);
- pr_info("attached %s%s\n", bdev_name,
- info->panic_write ? "" : " (no dedicated panic_write!)");
- return 0;
-
-err_put_bdev:
- psblk_bdev = NULL;
- blkdev_panic_write = NULL;
- psblk_put_bdev(bdev, holder);
- return ret;
-}
-
-/**
- * register_pstore_blk() - register block device to pstore/blk
- *
- * @info: details on the desired block device interface
- *
- * Return:
- * * 0 - OK
- * * Others - something error.
- */
-int register_pstore_blk(struct pstore_blk_info *info)
-{
- int ret;
-
- mutex_lock(&pstore_blk_lock);
- ret = __register_pstore_blk(info);
- mutex_unlock(&pstore_blk_lock);
-
- return ret;
-}
-EXPORT_SYMBOL_GPL(register_pstore_blk);
-
-static void __unregister_pstore_blk(unsigned int major)
-{
- struct pstore_device_info dev = { .read = psblk_generic_blk_read };
- void *holder = blkdev;
-
- lockdep_assert_held(&pstore_blk_lock);
- if (psblk_bdev && MAJOR(psblk_bdev->bd_dev) == major) {
- __unregister_pstore_device(&dev);
- psblk_put_bdev(psblk_bdev, holder);
- blkdev_panic_write = NULL;
- psblk_bdev = NULL;
- }
-}
-
-/**
- * unregister_pstore_blk() - unregister block device from pstore/blk
- *
- * @major: the major device number of device
- */
-void unregister_pstore_blk(unsigned int major)
-{
- mutex_lock(&pstore_blk_lock);
- __unregister_pstore_blk(major);
- mutex_unlock(&pstore_blk_lock);
-}
-EXPORT_SYMBOL_GPL(unregister_pstore_blk);
-
/* get information of pstore/blk */
int pstore_blk_get_config(struct pstore_blk_config *info)
{
@@ -481,32 +212,14 @@ int pstore_blk_get_config(struct pstore_blk_config *info)
}
EXPORT_SYMBOL_GPL(pstore_blk_get_config);
-static int __init pstore_blk_init(void)
-{
- struct pstore_blk_info info = { };
- int ret = 0;
-
- mutex_lock(&pstore_blk_lock);
- if (!pstore_zone_info && best_effort && blkdev[0])
- ret = __register_pstore_blk(&info);
- mutex_unlock(&pstore_blk_lock);
-
- return ret;
-}
-late_initcall(pstore_blk_init);
-
static void __exit pstore_blk_exit(void)
{
- mutex_lock(&pstore_blk_lock);
- if (psblk_bdev)
- __unregister_pstore_blk(MAJOR(psblk_bdev->bd_dev));
- else {
- struct pstore_device_info dev = { };
+ struct pstore_device_info dev = { };
- if (pstore_zone_info)
- dev.read = pstore_zone_info->read;
- __unregister_pstore_device(&dev);
- }
+ mutex_lock(&pstore_blk_lock);
+ if (pstore_zone_info)
+ dev.read = pstore_zone_info->read;
+ __unregister_pstore_device(&dev);
mutex_unlock(&pstore_blk_lock);
}
module_exit(pstore_blk_exit);
diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
index 61e914522b0193..9a9bf76ea73960 100644
--- a/include/linux/pstore_blk.h
+++ b/include/linux/pstore_blk.h
@@ -22,33 +22,6 @@
typedef int (*pstore_blk_panic_write_op)(const char *buf, sector_t start_sect,
sector_t sects);
-/**
- * struct pstore_blk_info - pstore/blk registration details
- *
- * @major: Which major device number to support with pstore/blk
- * @flags: The supported PSTORE_FLAGS_* from linux/pstore.h.
- * @panic_write:The write operation only used for the panic case.
- * This can be NULL, but is recommended to avoid losing
- * crash data if the kernel's IO path or work queues are
- * broken during a panic.
- * @devt: The dev_t that pstore/blk has attached to.
- * @nr_sects: Number of sectors on @devt.
- * @start_sect: Starting sector on @devt.
- */
-struct pstore_blk_info {
- unsigned int major;
- unsigned int flags;
- pstore_blk_panic_write_op panic_write;
-
- /* Filled in by pstore/blk after registration. */
- dev_t devt;
- sector_t nr_sects;
- sector_t start_sect;
-};
-
-int register_pstore_blk(struct pstore_blk_info *info);
-void unregister_pstore_blk(unsigned int major);
-
/**
* struct pstore_device_info - back-end pstore/blk driver structure.
*
