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authorDavid Howells <dhowells@redhat.com>2025-03-14 19:41:56 +0300
committerChristian Brauner <brauner@kernel.org>2025-03-19 12:04:22 +0300
commitf298e37655288272fad3766b82db0c3c03facbf9 (patch)
tree35c8e2995882ff8d73d7db224286c5eee668d9cd /tools/perf/scripts/python/parallel-perf.py
parentd9ecc77193cad25402ff5517fb26fb22b4db0e10 (diff)
downloadlinux-f298e37655288272fad3766b82db0c3c03facbf9.tar.xz
netfs: Fix collection of results during pause when collection offloaded
A netfs read request can run in one of two modes: for synchronous reads writes, the app thread does the collection of results and for asynchronous reads, this is offloaded to a worker thread. This is controlled by the NETFS_RREQ_OFFLOAD_COLLECTION flag. Now, if a subrequest incurs an error, the NETFS_RREQ_PAUSE flag is set to stop the issuing loop temporarily from issuing more subrequests until a retry is successful or the request is abandoned. When the issuing loop sees NETFS_RREQ_PAUSE, it jumps to netfs_wait_for_pause() which will wait for the PAUSE flag to be cleared - and whilst it is waiting, it will call out to the collector as more results acrue... But this is the wrong thing to do if OFFLOAD_COLLECTION is set as we can then end up with both the app thread and the work item collecting results simultaneously. This manifests itself occasionally when running the generic/323 xfstest against multichannel cifs as an oops that's a bit random but frequently involving io_submit() (the test does lots of simultaneous async DIO reads). Fix this by only doing the collection in netfs_wait_for_pause() if the NETFS_RREQ_OFFLOAD_COLLECTION is not set. Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Reported-by: Steve French <stfrench@microsoft.com> Signed-off-by: David Howells <dhowells@redhat.com> Link: https://lore.kernel.org/r/20250314164201.1993231-2-dhowells@redhat.com Acked-by: "Paulo Alcantara (Red Hat)" <pc@manguebit.com> cc: Paulo Alcantara <pc@manguebit.com> cc: Jeff Layton <jlayton@kernel.org> cc: linux-cifs@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org>
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