Re: [PATCH] btrfs: remove unnecessary attempt do drop extent maps after adding inline extent

[Josef Bacik <josef@toxicpanda.com>]

On 11/13/20 6:24 AM, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> At inode.c:cow_file_range_inline(), after we insert the inline extent
> in the fs/subvolume btree, we call btrfs_drop_extent_cache() to drop
> all extent maps in the file range, however that is not necessary because
> we have already done it in the call to btrfs_drop_extents(), which calls
> btrfs_drop_extent_cache() for us, and since at this point we have the file
> range locked in the inode's iotree (we are in the writeback path), we know
> no other task can come in and read stale file extent items or find none
> and therefore create either stale extent maps or an extent map that
> represens a hole.
> 
> So just remove that unnecessary call to btrfs_drop_extent_cache(), as it's
> doing nothing and only wasting time. This call has been around since 2008,
> introduced in commit c8b978188c9a ("Btrfs: Add zlib compression support"),
> but even back then it seems it was not necessary, since we had the range
> locked in the inode's iotree and the call to btrfs_drop_extents() already
> used to always call btrfs_drop_extent_cache().
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef