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    Subject[PATCH 7/9] pmem: Add support for page structs
    From: Boaz Harrosh <boaz@plexistor.com>

    One of the current shortcomings of the NVDIMM/PMEM
    support is that this memory does not have a page-struct(s)
    associated with its memory and therefor cannot be passed
    to a block-device or network or DMAed in any way through
    another device in the system.

    The use of add_persistent_memory() fixes all this. After this patch
    an FS can do:
    bdev_direct_access(,&pfn,);
    page = pfn_to_page(pfn);
    And use that page for a lock_page(), set_page_dirty(), and/or
    anything else one might do with a page *.
    (Note that with brd one can already do this)

    [pmem-pages-ref-count]
    pmem will serve it's pages with ref==0. Once an FS does
    an blkdev_get_XXX(,FMODE_EXCL,), that memory is own by the FS.
    The FS needs to manage its allocation, just as it already does
    for its disk blocks. The fs should set page->count = 2, before
    submission to any Kernel subsystem so when it returns it will
    never be released to the Kernel's page-allocators. (page_freeze)

    Signed-off-by: Boaz Harrosh <boaz@plexistor.com>
    ---
    drivers/block/Kconfig | 13 +++++++++++++
    drivers/block/pmem.c | 19 +++++++++++++++++++
    2 files changed, 32 insertions(+)

    diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
    index 5da8cbf..8a5929c 100644
    --- a/drivers/block/Kconfig
    +++ b/drivers/block/Kconfig
    @@ -416,6 +416,19 @@ config BLK_DEV_PMEM
    Most normal users won't need this functionality, and can thus say N
    here.

    +config BLK_DEV_PMEM_USE_PAGES
    + bool "Enable use of page struct pages with pmem"
    + depends on BLK_DEV_PMEM
    + depends on PERSISTENT_MEMORY_DEPENDENCY
    + select DRIVER_NEEDS_PERSISTENT_MEMORY
    + default y
    + help
    + If a user of PMEM device needs "struct page" associated
    + with its memory, so this memory can be sent to other
    + block devices, or sent on the network, or be DMA transferred
    + to other devices in the system, then you must say "Yes" here.
    + If unsure leave as Yes.
    +
    config CDROM_PKTCDVD
    tristate "Packet writing on CD/DVD media"
    depends on !UML
    diff --git a/drivers/block/pmem.c b/drivers/block/pmem.c
    index e07a373..b415b61 100644
    --- a/drivers/block/pmem.c
    +++ b/drivers/block/pmem.c
    @@ -221,6 +221,23 @@ MODULE_PARM_DESC(map,
    static LIST_HEAD(pmem_devices);
    static int pmem_major;

    +#ifdef CONFIG_BLK_DEV_PMEM_USE_PAGES
    +/* pmem->phys_addr and pmem->size need to be set.
    + * Will then set pmem->virt_addr if successful.
    + */
    +int pmem_mapmem(struct pmem_device *pmem)
    +{
    + return add_persistent_memory(pmem->phys_addr, pmem->size,
    + &pmem->virt_addr);
    +}
    +
    +static void pmem_unmapmem(struct pmem_device *pmem)
    +{
    + remove_persistent_memory(pmem->phys_addr, pmem->size);
    +}
    +
    +#else /* !CONFIG_BLK_DEV_PMEM_USE_PAGES */
    +
    /* pmem->phys_addr and pmem->size need to be set.
    * Will then set virt_addr if successful.
    */
    @@ -258,6 +275,8 @@ void pmem_unmapmem(struct pmem_device *pmem)
    release_mem_region(pmem->phys_addr, pmem->size);
    pmem->virt_addr = NULL;
    }
    +#endif /* ! CONFIG_BLK_DEV_PMEM_USE_PAGES */
    +

    static struct pmem_device *pmem_alloc(phys_addr_t phys_addr, size_t disk_size,
    int i)
    --
    1.9.3



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