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In the buffer write path, iomap_set_range_uptodate() is called every time iomap_end_write() is called. But if folio_test_uptodate() holds, we know that all blocks in this folio are already in the uptodate state, so there is no need to go deep into the critical section of state_lock to execute bitmap_set(). This is because the folios always creep towards ifs_is_fully_uptodate() state and once they've gotten there folio_mark_uptodate() is called, which means the folio is uptodate. Then once a folio is uptodate, there is no route back to !uptodate without going through the removal of the folio from the page cache. Therefore, it's fine to use folio_test_uptodate() to short-circuit unnecessary code paths. Although state_lock may not have significant lock contention due to folio lock, this patch at least reduces the number of instructions, especially the expensive lock-prefixed instructions. Signed-off-by: Jinliang Zheng <alexjlzheng@tencent.com> Link: https://lore.kernel.org/20250711081207.1782667-1-alexjlzheng@tencent.com Reviewed-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@infradead.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner <brauner@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.