On Wed, Jul 31, 2024 at 05:13:04PM +0800, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@xxxxxxxxxx>
>
> Commit '1cea335d1db1 ("iomap: fix sub-page uptodate handling")' fix a
> race issue when submitting multiple read bios for a page spans more than
> one file system block by adding a spinlock(which names state_lock now)
> to make the page uptodate synchronous. However, the race condition only
> happened between the read I/O submitting and completeing threads,
when we do writeback on a folio that has multiple blocks on it we
can submit multiple bios for that, too. Hence the write completions
can race with each other and write submission, too.
Yes, write bio submission and completion only need to update ifs
accounting using an atomic operation, but the same race condition
exists even though the folio is fully locked at the point of bio
submission.
> it's
> sufficient to use page lock to protect other paths, e.g. buffered write
^^^^ folio
> path.
>
> After large folio is supported, the spinlock could affect more
> about the buffered write performance, so drop it could reduce some
> unnecessary locking overhead.
