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    Subject[patch V3 27/37] x86/crashdump/32: Simplify copy_oldmem_page()
    Replace kmap_atomic_pfn() with kmap_local_pfn() which is preemptible and
    can take page faults.

    Remove the indirection of the dump page and the related cruft which is not
    longer required.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    V3: New patch
    ---
    arch/x86/kernel/crash_dump_32.c | 48 ++++++++--------------------------------
    1 file changed, 10 insertions(+), 38 deletions(-)

    --- a/arch/x86/kernel/crash_dump_32.c
    +++ b/arch/x86/kernel/crash_dump_32.c
    @@ -13,8 +13,6 @@

    #include <linux/uaccess.h>

    -static void *kdump_buf_page;
    -
    static inline bool is_crashed_pfn_valid(unsigned long pfn)
    {
    #ifndef CONFIG_X86_PAE
    @@ -41,15 +39,11 @@ static inline bool is_crashed_pfn_valid(
    * @userbuf: if set, @buf is in user address space, use copy_to_user(),
    * otherwise @buf is in kernel address space, use memcpy().
    *
    - * Copy a page from "oldmem". For this page, there is no pte mapped
    - * in the current kernel. We stitch up a pte, similar to kmap_atomic.
    - *
    - * Calling copy_to_user() in atomic context is not desirable. Hence first
    - * copying the data to a pre-allocated kernel page and then copying to user
    - * space in non-atomic context.
    + * Copy a page from "oldmem". For this page, there might be no pte mapped
    + * in the current kernel.
    */
    -ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
    - size_t csize, unsigned long offset, int userbuf)
    +ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
    + unsigned long offset, int userbuf)
    {
    void *vaddr;

    @@ -59,38 +53,16 @@ ssize_t copy_oldmem_page(unsigned long p
    if (!is_crashed_pfn_valid(pfn))
    return -EFAULT;

    - vaddr = kmap_atomic_pfn(pfn);
    + vaddr = kmap_local_pfn(pfn);

    if (!userbuf) {
    - memcpy(buf, (vaddr + offset), csize);
    - kunmap_atomic(vaddr);
    + memcpy(buf, vaddr + offset, csize);
    } else {
    - if (!kdump_buf_page) {
    - printk(KERN_WARNING "Kdump: Kdump buffer page not"
    - " allocated\n");
    - kunmap_atomic(vaddr);
    - return -EFAULT;
    - }
    - copy_page(kdump_buf_page, vaddr);
    - kunmap_atomic(vaddr);
    - if (copy_to_user(buf, (kdump_buf_page + offset), csize))
    - return -EFAULT;
    + if (copy_to_user(buf, vaddr + offset, csize))
    + csize = -EFAULT;
    }

    - return csize;
    -}
    + kunmap_local(vaddr);

    -static int __init kdump_buf_page_init(void)
    -{
    - int ret = 0;
    -
    - kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
    - if (!kdump_buf_page) {
    - printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
    - " page\n");
    - ret = -ENOMEM;
    - }
    -
    - return ret;
    + return csize;
    }
    -arch_initcall(kdump_buf_page_init);
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