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* [SCSI] scsi_dh: fix kconfig related build errorsChandra Seetharaman2008-07-151-1/+11
| | | | | | | | | | | | | | Do not automatically "select" SCSI_DH for dm-multipath. If SCSI_DH doesn't exist,just do not allow hardware handlers to be used. Handle SCSI_DH being a module also. Make sure it doesn't allow DM_MULTIPATH to be compiled in when SCSI_DH is a module. [jejb: added comment for Kconfig syntax] Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com> Reported-by: Randy Dunlap <randy.dunlap@oracle.com> Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
* [SCSI] scsi_dh: add infrastructure for SCSI Device HandlersChandra Seetharaman2008-06-051-0/+59
Some of the storage devices (that can be accessed through multiple paths), do need some special handling for 1. Activating the passive path of the storage access. 2. Decode and handle the special sense codes returned by the devices. 3. Handle the I/Os being sent to the passive path, especially during the device probe time. when accessed through multiple paths. As of today this special device handling is done at the dm-multipath layer using dm-handlers. That works well for (1); for (2) to be handled at dm layer, scsi sense information need to be exported from SCSI to dm-layer, which is not very attractive; (3) cannot be done at all at the dm layer. Device handler has been moved to SCSI mainly to handle (2) and (3) properly. Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com> Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com> Signed-off-by: Mike Christie <michaelc@cs.wisc.edu> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
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