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In the current glock reference counting model, a bias of one is added to a glock's refcount when it is locked (gl->gl_state != LM_ST_UNLOCKED). A glock is removed from the lru_list when it is enqueued, and added back when it is dequeued. This isn't a very appropriate model because most glocks are held for long periods of time (for example, the inode "owns" references to its inode and iopen glocks as long as the inode is cached even when the glock state changes to LM_ST_UNLOCKED), and they can only be freed when they are no longer referenced, anyway. Fix this by getting rid of the refcount bias for locked glocks. That way, we can use lockref_put_or_lock() to efficiently drop all but the last glock reference, and put the glock onto the lru_list when the last reference is dropped. When find_insert_glock() returns a reference to a cached glock, it removes the glock from the lru_list. Dumping the "glocks" and "glstats" debugfs files also takes glock references, but instead of removing the glocks from the lru_list in that case as well, we leave them on the list. This ensures that dumping those files won't perturb the order of the glocks on the lru_list. In addition, when the last reference to an *unlocked* glock is dropped, we immediately free it; this preserves the preexisting behavior. If it later turns out that caching unlocked glocks is useful in some situations, we can change the caching strategy. It is currently unclear if a glock that has no active references can have the GLF_LFLUSH flag set. To make sure that such a glock won't accidentally be evicted due to memory pressure, we add a GLF_LFLUSH check to gfs2_dispose_glock_lru(). Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
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.