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commit3d4e738311upstream. dmz_fetch_mblock() called from dmz_get_mblock() has a race since the allocation of the new metadata block descriptor and its insertion in the cache rbtree with the READING state is not atomic. Two different contexts requesting the same block may end up each adding two different descriptors of the same block to the cache. Another problem for this function is that the BIO for processing the block read is allocated after the metadata block descriptor is inserted in the cache rbtree. If the BIO allocation fails, the metadata block descriptor is freed without first being removed from the rbtree. Fix the first problem by checking again if the requested block is not in the cache right before inserting the newly allocated descriptor, atomically under the mblk_lock spinlock. The second problem is fixed by simply allocating the BIO before inserting the new block in the cache. Finally, since dmz_fetch_mblock() also increments a block reference counter, rename the function to dmz_get_mblock_slow(). To be symmetric and clear, also rename dmz_lookup_mblock() to dmz_get_mblock_fast() and increment the block reference counter directly in that function rather than in dmz_get_mblock(). Fixes:3b1a94c88b("dm zoned: drive-managed zoned block device target") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.