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From https://lore.kernel.org/linux-nfs/aQHASIumLJyOoZGH@infradead.org/
On Wed, Oct 29, 2025 at 12:20:40AM -0700, Christoph Hellwig wrote:
> On Mon, Oct 27, 2025 at 12:18:30PM -0400, Mike Snitzer wrote:
> > LOCALIO's misaligned DIO will issue head/tail followed by O_DIRECT
> > middle (via AIO completion of that aligned middle). So out of order
> > relative to file offset.
>
> That's in general a really bad idea. It will obviously work, but
> both on SSDs and out of place write file systems it is a sure way
> to increase your garbage collection overhead a lot down the line.
Fix this by never issuing misaligned DIO out of order. This fix means
the DIO-aligned middle will only use AIO completion if there is no
misaligned end segment. Otherwise, all 3 segments of a misaligned DIO
will be issued without AIO completion to ensure file offset increases
properly for all partial READ or WRITE situations.
Factoring out nfs_local_iter_setup() helps standardize repetitive
nfs_local_iters_setup_dio() code and is inspired by cleanup work that
Chuck Lever did on the NFSD Direct code.
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.