Hello Marco,
On 31.05.23 19:23, Marco Felsch wrote:
> Hi Ahmad,
>
> On 23-05-31, Ahmad Fatoum wrote:
>> Starting with commit 7f9f45b9bfef ("devfs: Do not create overlapping
>> partitions"), any overlapping is disallowed. Overlapping can be useful
>> though to bridge the gap between partition described in DT and via
>> on-disk partition tables. Let's handle the case of identical partitions
>> specially and have it neither be an error or a duplicate partition, but
>> instead just return the existing partition. This existing partition will
>> be given a device tree node and thus enabling schemes like:
>>
>> &{/state} {
>> backend = <&state_part>;
>> };
>>
>> &mmc1 {
>> partitions {
>> compatible = "fixed-partitions";
>> #address-cells = <2>;
>> #size-cells = <2>;
>>
>> state_part: partition@5300000 {
>> label = "barebox-state";
>> /* will be folded with overlapping GPT partition if found */
>> reg = <0x0 0x5300000 0x0 0x100000>;
>> };
>> };
>> };
>>
>> Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
>> ---
>> fs/devfs-core.c | 50 ++++++++++++++++++++++++++++++++++++++-----------
>> 1 file changed, 39 insertions(+), 11 deletions(-)
>>
>> diff --git a/fs/devfs-core.c b/fs/devfs-core.c
>> index a0732dafca42..b3a274d01ee0 100644
>> --- a/fs/devfs-core.c
>> +++ b/fs/devfs-core.c
>> @@ -402,6 +402,12 @@ int devfs_remove(struct cdev *cdev)
>> return 0;
>> }
>>
>> +static bool region_identical(loff_t starta, loff_t lena,
>> + loff_t startb, loff_t lenb)
>> +{
>> + return starta == startb && lena == lenb;
>> +}
>> +
>> static bool region_overlap(loff_t starta, loff_t lena,
>> loff_t startb, loff_t lenb)
>> {
>> @@ -412,10 +418,22 @@ static bool region_overlap(loff_t starta, loff_t lena,
>> return 1;
>> }
>>
>> -static int check_overlap(struct cdev *cdev, const char *name, loff_t offset, loff_t size)
>> +/**
>> + * check_overlap() - check overlap with existing partitions
>> + * @cdev: parent cdev
>> + * @name: partition name for informational purposes on conflict
>> + * @offset: offset of new partition to be added
>> + * @size: size of new partition to be added
>> + *
>> + * Return: NULL if no overlapping partition found or overlapping
>> + * partition if and only if it's identical in offset and size
>> + * to an existing partition. Otherwise, PTR_ERR(-EINVAL).
>> + */
>> +static struct cdev *check_overlap(struct cdev *cdev, const char *name, loff_t offset, loff_t size)
>> {
>> struct cdev *cpart;
>> loff_t cpart_offset;
>> + int ret;
>>
>> list_for_each_entry(cpart, &cdev->partitions, partition_entry) {
>> cpart_offset = cpart->offset;
>> @@ -428,20 +446,28 @@ static int check_overlap(struct cdev *cdev, const char *name, loff_t offset, lof
>> if (cpart->mtd)
>> cpart_offset = cpart->mtd->master_offset;
>>
>> - if (region_overlap(cpart_offset, cpart->size,
>> - offset, size))
>> + if (region_identical(cpart_offset, cpart->size, offset, size)) {
>> + ret = 0;
>> goto conflict;
>> + }
>
> The 'goto conflict' is a bit misleading here since this is no conflict
> as you described within the commit message.
It's still a conflict, but one that can be resolved by returning the existing
partition.
> I would rather do:
>
> if (region_identical(cpart_offset, cpart->size, offset, size))
> goto out_identical;
>
> and replace the __pr_printk() by pr_debug(). This way you split
> __pr_printk() and drop the ternary operator. The rest lgtm.
The print line is going to be long anyway, so why not share it between
the two cases?
>
> Regards,
> Marco
>
>> +
>> + if (region_overlap(cpart_offset, cpart->size, offset, size)) {
>> + ret = -EINVAL;
>> + goto conflict;
>> + }
>> }
>>
>> - return 0;
>> + return NULL;
>>
>> conflict:
>> - pr_err("New partition %s (0x%08llx-0x%08llx) on %s "
>> - "overlaps with partition %s (0x%08llx-0x%08llx), not creating it\n",
>> - name, offset, offset + size - 1, cdev->name,
>> - cpart->name, cpart_offset, cpart_offset + cpart->size - 1);
>> + __pr_printk(ret ? MSG_WARNING : MSG_DEBUG,
>> + "New partition %s (0x%08llx-0x%08llx) on %s "
>> + "%s with partition %s (0x%08llx-0x%08llx), not creating it\n",
>> + name, offset, offset + size - 1, cdev->name,
>> + ret ? "conflicts" : "identical",
>> + cpart->name, cpart_offset, cpart_offset + cpart->size - 1);
>>
>> - return -EINVAL;
>> + return ret ? ERR_PTR(ret) : cpart;
>> }
>>
>> static struct cdev *__devfs_add_partition(struct cdev *cdev,
>> @@ -449,6 +475,7 @@ static struct cdev *__devfs_add_partition(struct cdev *cdev,
>> {
>> loff_t offset, size;
>> static struct cdev *new;
>> + struct cdev *overlap;
>>
>> if (cdev_by_name(partinfo->name))
>> return ERR_PTR(-EEXIST);
>> @@ -479,8 +506,9 @@ static struct cdev *__devfs_add_partition(struct cdev *cdev,
>> return ERR_PTR(-EINVAL);
>> }
>>
>> - if (check_overlap(cdev, partinfo->name, offset, size))
>> - return ERR_PTR(-EINVAL);
>> + overlap = check_overlap(cdev, partinfo->name, offset, size);
>> + if (overlap)
>> + return overlap;
>>
>> if (IS_ENABLED(CONFIG_MTD) && cdev->mtd) {
>> struct mtd_info *mtd;
>> --
>> 2.39.2
>>
>>
>>
>
--
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