diff options
Diffstat (limited to 'block/bdev.c')
-rw-r--r-- | block/bdev.c | 75 |
1 files changed, 74 insertions, 1 deletions
diff --git a/block/bdev.c b/block/bdev.c index 0daf14e50dd0..fc8d28d77495 100644 --- a/block/bdev.c +++ b/block/bdev.c @@ -30,6 +30,9 @@ #include "../fs/internal.h" #include "blk.h" +/* Should we allow writing to mounted block devices? */ +static bool bdev_allow_write_mounted = IS_ENABLED(CONFIG_BLK_DEV_WRITE_MOUNTED); + struct bdev_inode { struct block_device bdev; struct inode vfs_inode; @@ -730,7 +733,58 @@ void blkdev_put_no_open(struct block_device *bdev) { put_device(&bdev->bd_device); } - + +static bool bdev_writes_blocked(struct block_device *bdev) +{ + return bdev->bd_writers == -1; +} + +static void bdev_block_writes(struct block_device *bdev) +{ + bdev->bd_writers = -1; +} + +static void bdev_unblock_writes(struct block_device *bdev) +{ + bdev->bd_writers = 0; +} + +static bool bdev_may_open(struct block_device *bdev, blk_mode_t mode) +{ + if (bdev_allow_write_mounted) + return true; + /* Writes blocked? */ + if (mode & BLK_OPEN_WRITE && bdev_writes_blocked(bdev)) + return false; + if (mode & BLK_OPEN_RESTRICT_WRITES && bdev->bd_writers > 0) + return false; + return true; +} + +static void bdev_claim_write_access(struct block_device *bdev, blk_mode_t mode) +{ + if (bdev_allow_write_mounted) + return; + + /* Claim exclusive or shared write access. */ + if (mode & BLK_OPEN_RESTRICT_WRITES) + bdev_block_writes(bdev); + else if (mode & BLK_OPEN_WRITE) + bdev->bd_writers++; +} + +static void bdev_yield_write_access(struct block_device *bdev, blk_mode_t mode) +{ + if (bdev_allow_write_mounted) + return; + + /* Yield exclusive or shared write access. */ + if (mode & BLK_OPEN_RESTRICT_WRITES) + bdev_unblock_writes(bdev); + else if (mode & BLK_OPEN_WRITE) + bdev->bd_writers--; +} + /** * bdev_open_by_dev - open a block device by device number * @dev: device number of block device to open @@ -773,6 +827,10 @@ struct bdev_handle *bdev_open_by_dev(dev_t dev, blk_mode_t mode, void *holder, if (ret) goto free_handle; + /* Blocking writes requires exclusive opener */ + if (mode & BLK_OPEN_RESTRICT_WRITES && !holder) + return ERR_PTR(-EINVAL); + bdev = blkdev_get_no_open(dev); if (!bdev) { ret = -ENXIO; @@ -800,12 +858,16 @@ struct bdev_handle *bdev_open_by_dev(dev_t dev, blk_mode_t mode, void *holder, goto abort_claiming; if (!try_module_get(disk->fops->owner)) goto abort_claiming; + ret = -EBUSY; + if (!bdev_may_open(bdev, mode)) + goto abort_claiming; if (bdev_is_partition(bdev)) ret = blkdev_get_part(bdev, mode); else ret = blkdev_get_whole(bdev, mode); if (ret) goto put_module; + bdev_claim_write_access(bdev, mode); if (holder) { bd_finish_claiming(bdev, holder, hops); @@ -901,6 +963,8 @@ void bdev_release(struct bdev_handle *handle) sync_blockdev(bdev); mutex_lock(&disk->open_mutex); + bdev_yield_write_access(bdev, handle->mode); + if (handle->holder) bd_end_claim(bdev, handle->holder); @@ -1069,3 +1133,12 @@ void bdev_statx_dioalign(struct inode *inode, struct kstat *stat) blkdev_put_no_open(bdev); } + +static int __init setup_bdev_allow_write_mounted(char *str) +{ + if (kstrtobool(str, &bdev_allow_write_mounted)) + pr_warn("Invalid option string for bdev_allow_write_mounted:" + " '%s'\n", str); + return 1; +} +__setup("bdev_allow_write_mounted=", setup_bdev_allow_write_mounted); |