Re: [PATCH v4] btrfs: retry verity reads for not-uptodate Merkle folios

[Matthew Wilcox]

On Wed, Jul 22, 2026 at 10:54:35AM +0800, Yichong Chen wrote:
> btrfs_read_merkle_tree_page() can find a folio in the mapping that is not
> uptodate.  After taking the folio lock, the current code treats that state
> as a read error and returns -EIO.
> 
> That can make a previous transient read failure sticky.  If the failed read
> left a not-uptodate folio in the mapping, later callers find that folio and
> fail instead of retrying the read.
> 
> Keep the existing page-cache insertion and locking order, but retry the
> Merkle item read when a not-uptodate folio is found in the mapping.  Also
> unlock the folio when read_key_bytes() fails so that a later caller can
> lock it and retry the read.
> 
> Fixes: 06ed09351b67 ("btrfs: convert btrfs_read_merkle_tree_page() to use a folio")

I object to this Fixes line.  I didn't introduce this problem; it was
already there before 06ed09351b67.