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873555f04d
The btree write buffer flush code is prone to causing journal deadlock due to inefficient use and release of reservation space. Reservation is not pre-reserved for write buffered keys (as is done for key cache keys, for example), because the write buffer flush side uses a fast path that attempts insertion without need for any reservation at all. The write buffer flush attempts to deal with this by inserting keys using the BTREE_INSERT_JOURNAL_RECLAIM flag to return an error on journal reservations that require blocking. Upon first error, it falls back to a slow path that inserts in journal order and supports moving the associated journal pin forward. The problem is that under pathological conditions (i.e. smaller log, larger write buffer and journal reservation pressure), we've seen instances where the fast path fails fairly quickly without having completed many insertions, and then the slow path is unable to push the journal pin forward enough to free up the space it needs to completely flush the buffer. This problem is occasionally reproduced by fstest generic/333. To avoid this problem, update the fast path algorithm to skip key inserts that fail due to inability to acquire needed journal reservation without immediately breaking out of the loop. Instead, insert as many keys as possible, zap the sequence numbers to mark them as processed, and then fall back to the slow path to process the remaining set in journal order. This reduces the amount of journal reservation that might be required to flush the entire buffer and increases the odds that the slow path is able to move the journal pin forward and free up space as keys are processed. Signed-off-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev> |
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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.