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btrfs: refactor the zoned device handling in cow_file_range 

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 comment explaining the logic.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Christoph Hellwig 2023-06-28 17:31:41 +02:00 committed by David Sterba
parent 44962ca37c
commit 6e144bf16b
1 changed files with 31 additions and 27 deletions
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58
fs/btrfs/inode.c
View File

@ -1363,7 +1363,8 @@ 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;
}
@ -1394,6 +1395,31 @@ 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;
@ -1477,6 +1503,9 @@ 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:
@ -1485,21 +1514,6 @@ out_reserve:
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:
*
@ -1710,19 +1724,9 @@ static noinline int run_delalloc_zoned(struct btrfs_inode *inode,
while (start <= end) {
ret = cow_file_range(inode, locked_page, start, end, &done_offset,
true, false);
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);