Linux mainline fork with MSM8998 patches | https://mainline.space | Currently supported devices:
OnePlus 5/5T, Xiaomi Mi 6, F(x)tec Pro¹ (2019 QX1000 model) & Sony Xperia XZ Premium (UNTESTED!)
0cf9b244e7
For compressed write, we use a mechanism called async COW, which unlike regular run_delalloc_cow() or cow_file_range() will also unlock the first page. This mechanism allows us to continue handling next ranges, without waiting for the time consuming compression. But this has a problem for subpage case, as we could have the following delalloc range for a page: 0 32K 64K | |///////| |///////| \- A \- B In the above case, if we pass both ranges to cow_file_range_async(), both range A and range B will try to unlock the full page [0, 64K). And which one finishes later than the other one will try to do other page operations like end_page_writeback() on a unlocked page, triggering VM layer BUG_ON(). To make subpage compression work at least partially, here we add another restriction for it, only allow compression if the delalloc range is fully page aligned. By that, async extent is always ensured to unlock the first page exclusively, just like it used to be for regular sectorsize. In theory, we only need to make sure the delalloc range fully covers its first page, but the tail page will be locked anyway, blocking later writeback until the compression finishes. Thus here we choose to make sure the range is fully page aligned before doing the compression. In the future, we could optimize the situation by properly increasing subpage::writers number for the locked page, but that also means we need to change how we run delalloc range of page. (Instead of running each delalloc range we hit, we need to find and lock all delalloc ranges covering the page, then run each of them). Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
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| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
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| COPYING | ||
| CREDITS | ||
| Kbuild | ||
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| 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.
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.