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 <[email protected]>
---
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;
+ }
+
+ 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
