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The Coverity Scan service has detected potential
race conditions in ceph_block_o_direct(), ceph_start_io_read(),
ceph_block_buffered(), and ceph_start_io_direct() [1 - 4].
The CID 1590942, 1590665, 1589664, 1590377 contain explanation:
"The value of the shared data will be determined by
the interleaving of thread execution. Thread shared data is accessed
without holding an appropriate lock, possibly causing
a race condition (CWE-366)".
This patch reworks the pattern of accessing/modification of
CEPH_I_ODIRECT flag by means of adding smp_mb__before_atomic()
before reading the status of CEPH_I_ODIRECT flag and
smp_mb__after_atomic() after clearing set/clear this flag.
Also, it was reworked the pattern of using of ci->i_ceph_lock
in ceph_block_o_direct(), ceph_start_io_read(),
ceph_block_buffered(), and ceph_start_io_direct() methods.
[1] https://scan5.scan.coverity.com/#/project-view/64304/10063?selectedIssue=1590942
[2] https://scan5.scan.coverity.com/#/project-view/64304/10063?selectedIssue=1590665
[3] https://scan5.scan.coverity.com/#/project-view/64304/10063?selectedIssue=1589664
[4] https://scan5.scan.coverity.com/#/project-view/64304/10063?selectedIssue=1590377
Signed-off-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Reviewed-by: Alex Markuze <amarkuze@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
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This allows killing processes that wait for a lock when one process is
stuck waiting for the Ceph server. This is similar to the NFS commit
38a125b31504 ("fs/nfs/io: make nfs_start_io_*() killable").
[ idryomov: drop comment on include, formatting ]
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
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Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
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xfstest generic/451 intermittently fails. The test does O_DIRECT writes
to a file, and then reads back the result using buffered I/O, while
running a separate set of tasks that are also doing buffered reads.
The client will invalidate the cache prior to a direct write, but it's
easy for one of the other readers' replies to race in and reinstantiate
the invalidated range with stale data.
To fix this, we must to serialize direct I/O writes and buffered reads.
We could just sprinkle in some shared locks on the i_rwsem for reads,
and increase the exclusive footprint on the write side, but that would
cause O_DIRECT writes to end up serialized vs. other direct requests.
Instead, borrow the scheme used by nfs.ko. Buffered writes take the
i_rwsem exclusively, but buffered reads take a shared lock, allowing
them to run in parallel.
O_DIRECT requests also take a shared lock, but we need for them to not
run in parallel with buffered reads. A flag on the ceph_inode_info is
used to indicate whether it's in direct or buffered I/O mode. When a
conflicting request is submitted, it will block until the inode can be
flipped to the necessary mode.
Link: https://tracker.ceph.com/issues/40985
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
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