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The fops owned by the adapter can be corrupted in certain scenarios, opening a window where certain fops are temporarily NULLed before being reset to their proper value. This can potentially lead software to make incorrect decisions, leaving the user with the inability to function as intended. An example of this behavior can be observed when there are a number of users with a high rate of turn around (attach to LUN, perform an I/O, detach from LUN, repeat). Every so often a user is given a valid context and adapter file descriptor, but the file associated with the descriptor lacks the correct read permission bit (FMODE_CAN_READ) and thus the read system call bails before calling the valid read fop. Background: The fops is stored in the adapter structure to provide the ability to lookup the adapter structure from within the fop handler. CXL services use the file's private_data and at present, the CXL context does not have a private section. In an effort to limit areas of the cxlflash driver with code specific the superpipe function, a design choice was made to keep the details of the fops situated away from the legacy portions of the driver. This drove the behavior that the adapter fops is set at the beginning of the disk attach ioctl handler when there are no users present. The corruption that this fix remedies is due to the fact that the fops is initially defaulted to values found within a static structure. When the fops is handed down to the CXL services later in the attach path, certain services are patched. The fops structure remains correct until the user count drops to 0 and the fops is reset, triggering the process to repeat again. The user counts are tightly coupled with the creation and deletion of the user context. If multiple users perform a disk attach at the same time, when the user count is currently 0, some users can be in the middle of obtaining a file descriptor and have not yet reached the context creation code that [in addition to creating the context] increments the user count. Subsequent users coming in to perform the attach see that the user count is still 0, and reinitialize the fops, temporarily removing the patched fops. The users that are in the middle obtaining their file descriptor may then receive an invalid descriptor. The fix simply removes the user count altogether and moves the fops initialization to probe time such that it is only performed one time for the life of the adapter. In the future, if the CXL services adopt a private member for their context, that could be used to store the adapter structure reference and cxlflash could revert to a model that does not require an embedded fops. Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com> Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com> Reviewed-by: Brian King <brking@linux.vnet.ibm.com> Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com> Reviewed-by: Daniel Axtens <dja@axtens.net> Reviewed-by: Tomas Henzl <thenzl@redhat.com> Signed-off-by: James Bottomley <JBottomley@Odin.com> |
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| .. | ||
| common.h | ||
| Kconfig | ||
| lunmgt.c | ||
| main.c | ||
| main.h | ||
| Makefile | ||
| sislite.h | ||
| superpipe.c | ||
| superpipe.h | ||
| vlun.c | ||
| vlun.h | ||