From 68ff9b9b27525cdaaea81890456f65aed5ce0b70 Mon Sep 17 00:00:00 2001 From: Nicholas Bellinger Date: Mon, 19 Aug 2013 15:20:28 -0700 Subject: target: Add support for COMPARE_AND_WRITE emulation This patch adds support for COMPARE_AND_WRITE emulation on a per block basis. This logic is used as an atomic test and set primative currently used by VMWare ESX VAAI for performing array side locking of individual VMFS extent ownership. This includes the COMPARE_AND_WRITE CDB parsing within sbc_parse_cdb(), and does the majority of the work within the compare_and_write_callback() to perform the verify instance user data comparision, and subsequent write instance user data I/O submission upon a successfull comparision. The synchronization is enforced by se_device->caw_sem, that is obtained before the initial READ I/O submission in sbc_compare_and_write(). The mutex is then released upon MISCOMPARE in compare_and_write_callback(), or upon WRITE instance user-data completion in compare_and_write_post(). The implementation currently assumes a single logical block (NoLB=1). v4 changes: - Explicitly clear cmd->transport_complete_callback for two failure cases in sbc_compare_and_write() in order to avoid double unlock of ->caw_sem in compare_and_write_callback() (Dan Carpenter) v3 changes: - Convert se_device->caw_mutex to ->caw_sem v2 changes: - Set SCF_COMPARE_AND_WRITE and cmd->execute_cmd() to sbc_compare_and_write() during setup in sbc_parse_cdb() - Use sbc_compare_and_write() for initial READ submission with DMA_FROM_DEVICE - Reset cmd->execute_cmd() to sbc_execute_rw() for write instance user-data in compare_and_write_callback() - Drop SCF_BIDI command flag usage - Set TRANSPORT_PROCESSING + transport_state flags before write instance submission, and convert to __target_execute_cmd() - Prevent sbc_get_size() from being being called twice to generate incorrect size in sbc_parse_cdb() - Enforce se_device->caw_mutex synchronization between initial READ I/O submission, and final WRITE I/O completion. Cc: Christoph Hellwig Cc: Hannes Reinecke Cc: Martin Petersen Cc: Chris Mason Cc: James Bottomley Cc: Nicholas Bellinger Signed-off-by: Nicholas Bellinger --- include/target/target_core_base.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/target') diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h index 61a4dc890701..b5d0c2496c7e 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -672,6 +672,7 @@ struct se_device { spinlock_t se_port_lock; spinlock_t se_tmr_lock; spinlock_t qf_cmd_lock; + struct semaphore caw_sem; /* Used for legacy SPC-2 reservationsa */ struct se_node_acl *dev_reserved_node_acl; /* Used for ALUA Logical Unit Group membership */ -- cgit