On 10/9/19 5:38 PM, Matthew Bobrowski wrote:
On Wed, Oct 09, 2019 at 11:30:21AM +0530, Ritesh Harjani wrote:
+static u16 ext4_iomap_check_delalloc(struct inode *inode,
+ struct ext4_map_blocks *map)
+{
+ struct extent_status es;
+ ext4_lblk_t end = map->m_lblk + map->m_len - 1;
+
+ ext4_es_find_extent_range(inode, &ext4_es_is_delayed, map->m_lblk,
+ end, &es);
+
+ /* Entire range is a hole */
+ if (!es.es_len || es.es_lblk > end)
+ return IOMAP_HOLE;
+ if (es.es_lblk <= map->m_lblk) {
+ ext4_lblk_t offset = 0;
+
+ if (es.es_lblk < map->m_lblk)
+ offset = map->m_lblk - es.es_lblk;
+ map->m_lblk = es.es_lblk + offset;
This looks redundant no? map->m_lblk never changes actually.
So this is not needed here.
Well, it depends if map->m_lblk == es.es_lblk + offset prior to the
assignment? If that's always true, then sure, it'd be redundant. But
honestly, I don't know what the downstream effect would be if this was
removed. I'd have to look at the code, perform some tests, and figure
it out.
<snip>
3334 if (es.es_lblk <= map->m_lblk) {
3335 ext4_lblk_t offset = 0;
3336
3337 if (es.es_lblk < map->m_lblk)
3338 offset = map->m_lblk - es.es_lblk;
3339 map->m_lblk = es.es_lblk + offset;
3340 map->m_len = es.es_len - offset;
3341 return IOMAP_DELALLOC;
3342 }
I saw it this way-
In condition "if (es.es_lblk <= map->m_lblk)" there are 2 cases.
Case 1: es.es_lblk is equal to map->m_lblk (equality)
For this case, "offset" will remain 0.
So map->lblk = es.es_lblk + 0 (but since es.es_lblk is same as
map->m_lblk in equality case, so it is redundant).
Case 2: es.es_lblk < map->m_lblk (less than)
In this case "offset = map->m_lblk - es.es_lblk"
Now replacing this val of offset in "map->m_lblk = es.es_lblk + offset"
map->m_lblk = es.es_lblk + map->m_lblk - es.es_lblk
which again is map->m_lblk = map->m_lblk - again redundant.
What did I miss?
But sure feel free to test as per your convenience.
+ map.m_lblk = first_block;
+ map.m_len = last_block = first_block + 1;
+ ret = ext4_map_blocks(NULL, inode, &map, 0);
+ if (ret < 0)
+ return ret;
+ if (ret == 0)
+ type = ext4_iomap_check_delalloc(inode, &map);
+ return ext4_set_iomap(inode, iomap, type, first_block, &map);
We don't need to send first_block here. Since map->m_lblk
is same as first_block.
Also with Jan comment, we don't even need 'type' parameter.
Then we should be able to rename the function
ext4_set_iomap ==> ext4_map_to_iomap. This better reflects what it is
doing. Thoughts?
Depends on what we conclude in 1/8. :)
I'm for removing 'first_block', but still not convinced removing
'type' is heading down the right track if I were to forward think a
little.
Only once you are convinced that map->m_lblk will not change even in
function ext4_iomap_check_delalloc(), then only you should
drop "first_block" argument from ext4_set_iomap.
Please check above comments once.
-ritesh
