[PATCH 3/5] mtd: block2mtd: Fallback to read-only mode

Pali Rohár
2017-06-02T15:44:19Z

Sometimes block device is readonly (e.g. loopbacks). This patch allows
block2mtd to fallback and create read-only MTD_ROM device instead of
fatal failure.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
---
drivers/mtd/devices/block2mtd.c | 39 ++++++++++++++++++++++++++++++++-------
1 file changed, 32 insertions(+), 7 deletions(-)

diff --git a/drivers/mtd/devices/block2mtd.c b/drivers/mtd/devices/block2mtd.c
index 5ba5fad..ad96937 100644
--- a/drivers/mtd/devices/block2mtd.c
+++ b/drivers/mtd/devices/block2mtd.c
@@ -38,6 +38,7 @@ struct block2mtd_dev {
struct block_device *blkdev;
struct mtd_info mtd;
struct mutex write_mutex;
+ bool ro_mode;
};

@@ -212,7 +213,10 @@ static void block2mtd_free_device(struct block2mtd_dev *dev)
if (dev->blkdev) {
invalidate_mapping_pages(dev->blkdev->bd_inode->i_mapping,
0, -1);
- blkdev_put(dev->blkdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
+ if (dev->ro_mode)
+ blkdev_put(dev->blkdev, FMODE_READ);
+ else
+ blkdev_put(dev->blkdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
}

kfree(dev);
@@ -240,6 +244,13 @@ static struct block2mtd_dev *add_device(char *devname, uint32_t erase_size,
/* Get a handle on the device */
bdev = blkdev_get_by_path(devname, mode, dev);

+ /* Try fallback to read only mode */
+ if (IS_ERR(bdev)) {
+ bdev = blkdev_get_by_path(devname, FMODE_READ, dev);
+ if (!IS_ERR(bdev))
+ dev->ro_mode = true;
+ }
+
#ifndef MODULE
/*
* We might not have the root device mounted at this point.
@@ -261,6 +272,13 @@ static struct block2mtd_dev *add_device(char *devname, uint32_t erase_size,
if (!devt)
continue;
bdev = blkdev_get_by_dev(devt, mode, dev);
+
+ /* Try fallback to read only mode */
+ if (IS_ERR(bdev)) {
+ bdev = blkdev_get_by_path(devname, FMODE_READ, dev);
+ if (!IS_ERR(bdev))
+ dev->ro_mode = true;
+ }
}
#endif

@@ -295,16 +313,22 @@ static struct block2mtd_dev *add_device(char *devname, uint32_t erase_size,

dev->mtd.name = name;

+ if (dev->ro_mode) {
+ dev->mtd.type = MTD_ROM;
+ dev->mtd.flags = MTD_CAP_ROM;
+ } else {
+ dev->mtd.type = MTD_RAM;
+ dev->mtd.flags = MTD_CAP_RAM;
+ dev->mtd._erase = block2mtd_erase;
+ dev->mtd._write = block2mtd_write;
+ dev->mtd._sync = block2mtd_sync;
+ }
+
dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
dev->mtd.erasesize = erase_size;
dev->mtd.writesize = write_size;
dev->mtd.subpage_sft = subpage_sft;
dev->mtd.writebufsize = PAGE_SIZE;
- dev->mtd.type = MTD_RAM;
- dev->mtd.flags = MTD_CAP_RAM;
- dev->mtd._erase = block2mtd_erase;
- dev->mtd._write = block2mtd_write;
- dev->mtd._sync = block2mtd_sync;
dev->mtd._read = block2mtd_read;
dev->mtd.priv = dev;
dev->mtd.owner = THIS_MODULE;
@@ -315,9 +339,10 @@ static struct block2mtd_dev *add_device(char *devname, uint32_t erase_size,
}

list_add(&dev->list, &blkmtd_device_list);
- pr_info("mtd%d: [%s] erase_size = %dKiB [%d], write_size = %dKiB [%d], subpage_sft = %d\n",
+ pr_info("mtd%d: [%s] mode = %s, erase_size = %dKiB [%d], write_size = %dKiB [%d], subpage_sft = %d\n",
dev->mtd.index,
dev->mtd.name + strlen("block2mtd: "),
+ (dev->ro_mode ? "RO" : "R/W"),
dev->mtd.erasesize >> 10, dev->mtd.erasesize,
dev->mtd.writesize >> 10, dev->mtd.writesize,
dev->mtd.subpage_sft);
--
1.7.9.5