9pfs: fix off-by-one error in PDU free list
The server can handle MAX_REQ - 1 PDUs at a time and the virtio-9p device has a MAX_REQ sized virtqueue. If the client manages to fill up the virtqueue, pdu_alloc() will fail and the request won't be processed without any notice to the client (it actually causes the linux 9p client to hang). This has been there since the beginning (commit 9f107513 "virtio-9p: Add a virtio 9p device to qemu"), but it needs an agressive workload to run in the guest to show up. We actually allocate MAX_REQ PDUs and I see no reason not to link them all into the free list, so let's fix the init loop. Reported-by: NTuomas Tynkkynen <tuomas@tuxera.com> Suggested-by: NAl Viro <viro@ZenIV.linux.org.uk> Signed-off-by: NGreg Kurz <groug@kaod.org> (cherry picked from commit 0d78289c) Conflicts: hw/9pfs/9p.c * drop context dep on 583f21f8Signed-off-by: NGreg Kurz <groug@kaod.org> Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>
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