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In cow_file_range(), after we have succeeded creating an inline extent, we unlock the page with extent_clear_unlock_delalloc() by passing locked_page == NULL. For sectorsize == PAGE_SIZE case, this is just making the page lock and unlock harder to grab. But for incoming subpage case, it can be a big problem. For incoming subpage case, page locking have two entry points: - __process_pages_contig() In that case, we know exactly the range we want to lock (which only requires sector alignment). To handle the subpage requirement, we introduce btrfs_subpage::writers to page::private, and will update it in __process_pages_contig(). - Other directly lock/unlock_page() call sites Those won't touch btrfs_subpage::writers at all. This means, page locked by __process_pages_contig() can only be unlocked by __process_pages_contig(). Thankfully we already have the existing infrastructure in the form of @locked_page in various call sites. Unfortunately, extent_clear_unlock_delalloc() in cow_file_range() after creating an inline extent is the exception. It intentionally call extent_clear_unlock_delalloc() with locked_page == NULL, to also unlock current page (and clear its dirty/writeback bits). To co-operate with incoming subpage modifications, and make the page lock/unlock pair easier to understand, this patch will still call extent_clear_unlock_delalloc() with locked_page, and only unlock the page in __extent_writepage(). Tested-by: Ritesh Harjani <riteshh@linux.ibm.com> # [ppc64] Tested-by: Anand Jain <anand.jain@oracle.com> # [aarch64] Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> |
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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.