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For btrfs with sector size < page size (e.g. 4K sector size, 64K page
size), and enable the sector perfect compression support, then the
following dirty range can lead to problems:
0 32K 64K 96K 128K
| |///////||//////| |/|
124K
In above case, if we start writeback for that inode, the last dirty
range [124K, 128K) will not be submitted and cause reserved space
leakage:
- Start writeback for page 0
We find the range [32K, 96K) is suitable for compression, and queue it
into a workqueue to do the delayed compression and submission.
- Compression happens for range [32K, 96K)
Function extent_range_clear_dirty_for_io() is called, however it is
only doing full page handling, not considering any the extra bitmaps
for subpage cases.
That function will clear page dirty for both page 0 and page 64K.
- Writeback for the inode is done
Because page 64K has its dirty flag cleared, it will not be considered
as a writeback target.
This means the range [124K, 128K) will not be submitted, and reserved
space for it will be leaked.
Fix this problem by using the subpage helper to clear the dirty flag.
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 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.