84ca484ecf
Unwritten extents by definition have not been written to until they are converted to normal written extents. If unwritten extents are freed from a file, it is therefore guaranteed that the blocks have not been written to since allocation (note that zero range punches and reallocates blocks). To cut down on online discards generated from workloads that make use of preallocation, skip discards of extents if they are in the unwritten state when the extent is freed. Note that this optimization does not apply to log recovery, during which all freed extents are discarded if online discard is enabled. Also note that it may be possible for a filesystem crash to occur after write completion of an unwritten extent but before unwritten conversion such that the extent remains unwritten after log recovery. Since this pseudo-inconsistency may already be possible after a crash (consider writing to recently allocated blocks where the allocation transaction is lost after a crash), this change shouldn't introduce any fundamental limitations that don't already exist. In short, on storage stacks where discards are important, it's good practice to run an occasional fstrim even with online discard enabled in the filesystem, particularly after a crash. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> |
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| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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 Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
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.