Handling of the done_offset to cow_file_range is a bit confusing, as
it is not updated at all when the function succeeds, and the -EAGAIN
status is used bother for the case where we need to wait for a zone
finish and the one where the allocation was partially successful.
Change the calling convention so that done_offset is always updated,
and 0 is returned if some allocation was successful (partial allocation
can still only happen for zoned devices), and waiting for a zone
finish is done internally in cow_file_range instead of the caller.
Also write a big fat comment explaining the logic.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/btrfs/inode.c | 58 ++++++++++++++++++++++++++----------------------
1 file changed, 31 insertions(+), 27 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 556f63e8496ff8..2a4b62398ee7a3 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1364,7 +1364,8 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
* compressed extent.
*/
unlock_page(locked_page);
- return 1;
+ ret = 1;
+ goto done;
} else if (ret < 0) {
goto out_unlock;
}
@@ -1395,6 +1396,31 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
ret = btrfs_reserve_extent(root, cur_alloc_size, cur_alloc_size,
min_alloc_size, 0, alloc_hint,
&ins, 1, 1);
+ if (ret == -EAGAIN) {
+ /*
+ * btrfs_reserve_extent only returns -EAGAIN for zoned
+ * file systems, which is an indication that there are
+ * no active zones to allocate from at the moment.
+ *
+ * If this is the first loop iteration, wait for at
+ * least one zone to finish before retrying the
+ * allocation. Otherwise ask the caller to write out
+ * the already allocated blocks before coming back to
+ * us, or return -ENOSPC if it can't handle retries.
+ */
+ ASSERT(btrfs_is_zoned(fs_info));
+ if (start == orig_start) {
+ wait_on_bit_io(&inode->root->fs_info->flags,
+ BTRFS_FS_NEED_ZONE_FINISH,
+ TASK_UNINTERRUPTIBLE);
+ continue;
+ }
+ if (done_offset) {
+ *done_offset = start - 1;
+ return 0;
+ }
+ ret = -ENOSPC;
+ }
if (ret < 0)
goto out_unlock;
cur_alloc_size = ins.offset;
@@ -1478,6 +1504,9 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
if (ret)
goto out_unlock;
}
+done:
+ if (done_offset)
+ *done_offset = end;
return ret;
out_drop_extent_cache:
@@ -1486,21 +1515,6 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
btrfs_dec_block_group_reservations(fs_info, ins.objectid);
btrfs_free_reserved_extent(fs_info, ins.objectid, ins.offset, 1);
out_unlock:
- /*
- * If done_offset is non-NULL and ret == -EAGAIN, we expect the
- * caller to write out the successfully allocated region and retry.
- */
- if (done_offset && ret == -EAGAIN) {
- if (orig_start < start)
- *done_offset = start - 1;
- else
- *done_offset = start;
- return ret;
- } else if (ret == -EAGAIN) {
- /* Convert to -ENOSPC since the caller cannot retry. */
- ret = -ENOSPC;
- }
-
/*
* Now, we have three regions to clean up:
*
@@ -1711,19 +1725,9 @@ static noinline int run_delalloc_zoned(struct btrfs_inode *inode,
while (start <= end) {
ret = cow_file_range(inode, locked_page, start, end,
&done_offset, CFR_KEEP_LOCKED);
- if (ret && ret != -EAGAIN)
+ if (ret)
return ret;
- if (ret == 0)
- done_offset = end;
-
- if (done_offset == start) {
- wait_on_bit_io(&inode->root->fs_info->flags,
- BTRFS_FS_NEED_ZONE_FINISH,
- TASK_UNINTERRUPTIBLE);
- continue;
- }
-
if (!locked_page_done) {
__set_page_dirty_nobuffers(locked_page);
account_page_redirty(locked_page);
--
2.39.2
