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When reading a btree node (or leaf), at read_block_for_search(), if we can't find its extent buffer in the cache (the fs_info->buffer_radix radix tree), then we unlock all upper level nodes before reading the btree node/leaf from disk, to prevent blocking other tasks for too long. However if we find that the extent buffer is in the cache but it is not up to date, we don't unlock upper level nodes before reading it from disk, potentially blocking other tasks on upper level nodes for too long. Fix this inconsistent behaviour by unlocking upper level nodes if we need to read a node/leaf from disk because its in-memory extent buffer is not up to date. If we unlocked upper level nodes then we must return -EAGAIN to the caller, just like the case where the extent buffer is not cached in memory. And like that case, we determine if upper level nodes are locked by checking only if the parent node is locked - if it isn't, then no other upper level nodes are locked. This is actually a rare case, as if we have an extent buffer in memory, it typically has the uptodate flag set and passes all the checks done by btrfs_buffer_uptodate(). Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.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 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.