On Mon, May 17, 2021 at 11:21:49AM +0000, Johannes Thumshirn wrote:

On 17/05/2021 09:07, Johannes Thumshirn wrote:

quoted

quoted

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+	if (use_append) {
+		struct extent_map *em;
+		struct map_lookup *map;
+
+		em = btrfs_get_chunk_map(fs_info, disk_start, PAGE_SIZE);

The caller already does the em lookup, so this is duplicate, allocating
memory, taking locks and doing a tree lookup. All happening on write out
path so this seems heavy.

Right, I did not check this, sorry. Is it OK to add another patch as 
preparation swapping some of the parameters to btrfs_submit_compressed_write()
from the em? Otherwise btrfs_submit_compressed_write() will have 10 parameters
which sounds awefull.

Actually I can't do that. The caller does calls create_io_em() while this patch
needs to call brtfs_get_chunk_map(). The 'em' returned by create_io_em() does not
have em->map_lookup populated and we need the stripe's block device from 
em->map_lookup.

So it looks like we need to live with the additional memory allocation and locks.

Ok then, it's limited to zoned mode so the allocation won't affect
regular mode.