| Message ID | 4F2BE3C1.8000104@parrot.com |
|---|---|
| State | RFC |
| Headers | show |
On Fri, 2012-02-03 at 14:40 +0100, Matthieu CASTET wrote: > Hi, > > it could be interesting to attach ubi in read-only mode (for example getting ubi > volume info without altering flash). > > A solution to do that could be to add an argument to UBI_IOCATT ioctl. No objections in general, especially if you also: 1. amend the mtd-utils and add support for this option 2. add a piece of doc for the mtd web site 3. add a test for this feature to mtd-utils.git/tests/ubi-test/ (probably simpler to improve one of the existing tests there) > Another solution should be to have a way to switch MTD_WRITEABLE flags. This can be done as well, up to you. But I guess UBI will need changes anyway to handle gracefully situation like: 1. you have RW partition, do a lot of I/O, then reboot uncleanly, so that there are many erase operations unfinished 2. You reboot, mark the partition R/O, try to attach it - UBI will probably anyway try to erase some blocks and get -EFORS, not sure will it panic or not. Should be tested, but probably not a big deal. IOW, both approaches should be OK.
Dear Matthieu CASTET, > Hi, > > it could be interesting to attach ubi in read-only mode (for example > getting ubi volume info without altering flash). > > A solution to do that could be to add an argument to UBI_IOCATT ioctl. > > Another solution should be to have a way to switch MTD_WRITEABLE flags. > > What do you think a that ? > > > PS : attached a proof of concept for solution 1 Did you get any further with this patches? Is it now possible to safely mount UBIFS in read-only mode in some way please? Thanks! Best regards, Marek Vasut
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c index 13b05cb..56c2249 100644 --- a/drivers/mtd/ubi/build.c +++ b/drivers/mtd/ubi/build.c @@ -841,6 +841,7 @@ static int autoresize(struct ubi_device *ubi, int vol_id) * @mtd: MTD device description object * @ubi_num: number to assign to the new UBI device * @vid_hdr_offset: VID header offset + * @ro : attach in readonly mode * * This function attaches MTD device @mtd_dev to UBI and assign @ubi_num number * to the newly created UBI device, unless @ubi_num is %UBI_DEV_NUM_AUTO, in @@ -851,7 +852,7 @@ static int autoresize(struct ubi_device *ubi, int vol_id) * Note, the invocations of this function has to be serialized by the * @ubi_devices_mutex. */ -int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset) +int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset, int ro) { struct ubi_device *ubi; int i, err, ref = 0; @@ -922,6 +923,12 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset) ubi_msg("attaching mtd%d to ubi%d", mtd->index, ubi_num); + if (ro) { + ubi_msg("attach in " + "read-only mode"); + ubi->ro_mode = 1; + } + err = io_init(ubi); if (err) goto out_free; @@ -1209,7 +1216,7 @@ static int __init ubi_init(void) mutex_lock(&ubi_devices_mutex); err = ubi_attach_mtd_dev(mtd, UBI_DEV_NUM_AUTO, - p->vid_hdr_offs); + p->vid_hdr_offs, 0); mutex_unlock(&ubi_devices_mutex); if (err < 0) { ubi_err("cannot attach mtd%d", mtd->index); diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c index 4dfa6b9..9be009f 100644 --- a/drivers/mtd/ubi/cdev.c +++ b/drivers/mtd/ubi/cdev.c @@ -1007,7 +1007,7 @@ static long ctrl_cdev_ioctl(struct file *file, unsigned int cmd, * 'ubi_attach_mtd_dev()'. */ mutex_lock(&ubi_devices_mutex); - err = ubi_attach_mtd_dev(mtd, req.ubi_num, req.vid_hdr_offset); + err = ubi_attach_mtd_dev(mtd, req.ubi_num, req.vid_hdr_offset, req.padding[0]); mutex_unlock(&ubi_devices_mutex); if (err < 0) put_mtd_device(mtd); diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h index a637f02..aff929f 100644 --- a/drivers/mtd/ubi/ubi.h +++ b/drivers/mtd/ubi/ubi.h @@ -550,7 +550,7 @@ int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum, struct ubi_vid_hdr *vid_hdr); /* build.c */ -int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset); +int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset, int ro); int ubi_detach_mtd_dev(int ubi_num, int anyway); struct ubi_device *ubi_get_device(int ubi_num); void ubi_put_device(struct ubi_device *ubi);