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pstore/blk: Use the normal block device I/O path
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Stop poking into block layer internals and just open the block device
file an use kernel_read and kernel_write on it. Note that this means
the transformation from name_to_dev_t can't be used anymore when
pstore_blk is loaded as a module: a full filesystem device path name
must be used instead. Additionally removes ":internal:" kerndoc link,
since no such documentation remains.

Co-developed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
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@kees
kees committed Jun 16, 2021
1 parent 2a03ddb commit 7bb9557
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Showing 2 changed files with 83 additions and 184 deletions.
3 changes: 0 additions & 3 deletions Documentation/admin-guide/pstore-blk.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -227,8 +227,5 @@ For developer reference, here are all the important structures and APIs:
.. kernel-doc:: include/linux/pstore_zone.h
:internal:

.. kernel-doc:: fs/pstore/blk.c
:internal:

.. kernel-doc:: include/linux/pstore_blk.h
:internal:
264 changes: 83 additions & 181 deletions fs/pstore/blk.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,15 +8,16 @@

#include <linux/kernel.h>
#include <linux/module.h>
#include "../../block/blk.h"
#include <linux/blkdev.h>
#include <linux/string.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/pstore_blk.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/init_syscalls.h>
#include <linux/mount.h>
#include <linux/uio.h>

static long kmsg_size = CONFIG_PSTORE_BLK_KMSG_SIZE;
module_param(kmsg_size, long, 0400);
Expand Down Expand Up @@ -60,23 +61,25 @@ MODULE_PARM_DESC(best_effort, "use best effort to write (i.e. do not require sto
*
* Usually, this will be a partition of a block device.
*
* blkdev accepts the following variants:
* 1) <hex_major><hex_minor> device number in hexadecimal representation,
* with no leading 0x, for example b302.
* 2) /dev/<disk_name> represents the device number of disk
* 3) /dev/<disk_name><decimal> represents the device number
* blkdev accepts the following variants, when built as a module:
* 1) /dev/<disk_name> represents the device number of disk
* 2) /dev/<disk_name><decimal> represents the device number
* of partition - device number of disk plus the partition number
* 4) /dev/<disk_name>p<decimal> - same as the above, that form is
* 3) /dev/<disk_name>p<decimal> - same as the above, that form is
* used when disk name of partitioned disk ends on a digit.
* 5) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
*
* blkdev accepts the following variants when built into the kernel:
* 1) <hex_major><hex_minor> device number in hexadecimal representation,
* with no leading 0x, for example b302.
* 2) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
* unique id of a partition if the partition table provides it.
* The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
* partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
* filled hex representation of the 32-bit "NT disk signature", and PP
* is a zero-filled hex representation of the 1-based partition number.
* 6) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to
* 3) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to
* a partition with a known unique id.
* 7) <major>:<minor> major and minor number of the device separated by
* 4) <major>:<minor> major and minor number of the device separated by
* a colon.
*/
static char blkdev[80] = CONFIG_PSTORE_BLK_BLKDEV;
Expand All @@ -88,15 +91,9 @@ 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 file *psblk_file;
static struct pstore_zone_info *pstore_zone_info;

struct bdev_info {
dev_t devt;
sector_t nr_sects;
sector_t start_sect;
};

#define check_size(name, alignsize) ({ \
long _##name_ = (name); \
_##name_ = _##name_ <= 0 ? 0 : (_##name_ * 1024); \
Expand Down Expand Up @@ -219,203 +216,73 @@ 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 = bdev_nr_sectors(bdev);
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);
return kernel_read(psblk_file, buf, bytes, &pos);
}

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;
return kernel_write(psblk_file, buf, bytes, &pos);
}

/*
* This takes its configuration only from the module parameters now.
* See psblk_get_bdev() and blkdev.
*/
static int __register_pstore_blk(void)
static int __register_pstore_blk(const char *devpath)
{
char bdev_name[BDEVNAME_SIZE];
struct block_device *bdev;
struct pstore_device_info dev;
struct bdev_info binfo;
void *holder = blkdev;
struct pstore_device_info dev = {
.read = psblk_generic_blk_read,
.write = psblk_generic_blk_write,
};
struct inode *inode;
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);
psblk_file = filp_open(devpath, O_RDWR | O_DSYNC | O_NOATIME | O_EXCL, 0);
if (IS_ERR(psblk_file)) {
ret = PTR_ERR(psblk_file);
pr_err("failed to open '%s': %d!\n", devpath, ret);
goto err;
}

/* only allow driver matching the @blkdev */
if (!binfo.devt) {
pr_debug("no major\n");
ret = -ENODEV;
goto err_put_bdev;
inode = file_inode(psblk_file);
if (!S_ISBLK(inode->i_mode)) {
pr_err("'%s' is not block device!\n", devpath);
goto err_fput;
}

/* psblk_bdev must be assigned before register to pstore/blk */
psblk_bdev = bdev;

memset(&dev, 0, sizeof(dev));
dev.total_size = binfo.nr_sects << SECTOR_SHIFT;
dev.read = psblk_generic_blk_read;
dev.write = psblk_generic_blk_write;
inode = I_BDEV(psblk_file->f_mapping->host)->bd_inode;
dev.total_size = i_size_read(inode);

ret = __register_pstore_device(&dev);
if (ret)
goto err_put_bdev;
goto err_fput;

bdevname(bdev, bdev_name);
pr_info("attached %s (no dedicated panic_write!)\n", bdev_name);
return 0;

err_put_bdev:
psblk_bdev = NULL;
psblk_put_bdev(bdev, holder);
err_fput:
fput(psblk_file);
err:
psblk_file = NULL;

return ret;
}

static void __unregister_pstore_blk(unsigned int major)
static void __unregister_pstore_blk(struct file *device)
{
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) {
if (psblk_file && psblk_file == device) {
__unregister_pstore_device(&dev);
psblk_put_bdev(psblk_bdev, holder);
psblk_bdev = NULL;
fput(psblk_file);
psblk_file = NULL;
}
}

Expand All @@ -433,13 +300,48 @@ int pstore_blk_get_config(struct pstore_blk_config *info)
}
EXPORT_SYMBOL_GPL(pstore_blk_get_config);


#ifndef MODULE
static const char devname[] = "/dev/pstore-blk";
static __init const char *early_boot_devpath(const char *initial_devname)
{
/*
* During early boot the real root file system hasn't been
* mounted yet, and no device nodes are present yet. Use the
* same scheme to find the device that we use for mounting
* the root file system.
*/
dev_t dev = name_to_dev_t(initial_devname);

if (!dev) {
pr_err("failed to resolve '%s'!\n", initial_devname);
return initial_devname;
}

init_unlink(devname);
init_mknod(devname, S_IFBLK | 0600, new_encode_dev(dev));

return devname;
}
#else
static inline const char *early_boot_devpath(const char *initial_devname)
{
return initial_devname;
}
#endif

static int __init pstore_blk_init(void)
{
int ret = 0;

mutex_lock(&pstore_blk_lock);
if (!pstore_zone_info && best_effort && blkdev[0])
ret = __register_pstore_blk();
if (!pstore_zone_info && best_effort && blkdev[0]) {
ret = __register_pstore_blk(early_boot_devpath(blkdev));
if (ret == 0 && pstore_zone_info)
pr_info("attached %s:%s (%zu) (no dedicated panic_write!)\n",
pstore_zone_info->name, blkdev,
pstore_zone_info->total_size);
}
mutex_unlock(&pstore_blk_lock);

return ret;
Expand All @@ -449,8 +351,8 @@ 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));
if (psblk_file)
__unregister_pstore_blk(psblk_file);
else {
struct pstore_device_info dev = { };

Expand Down

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