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| author | Sumitra Sharma <sumitraartsy@gmail.com> | 2023-06-10 10:57:12 -0700 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-08-18 10:18:50 -0700 |
| commit | ae96e0cdc78c816b93f9617d65d144162692c09c (patch) | |
| tree | f94355563a9cb7303fe1b6fb8ecc63dc41623b03 /lib/test_hmm.c | |
| parent | f58a2dd8d5d01b3ece13af7915745b8e7de20afe (diff) | |
| download | lwn-ae96e0cdc78c816b93f9617d65d144162692c09c.tar.gz lwn-ae96e0cdc78c816b93f9617d65d144162692c09c.zip | |
lib: replace kmap() with kmap_local_page()
kmap() has been deprecated in favor of the kmap_local_page() due to high
cost, restricted mapping space, the overhead of a global lock for
synchronization, and making the process sleep in the absence of free
slots.
kmap_local_page() is faster than kmap() and offers thread-local and
CPU-local mappings, take pagefaults in a local kmap region and preserves
preemption by saving the mappings of outgoing tasks and restoring those of
the incoming one during a context switch.
The mappings are kept thread local in the functions “dmirror_do_read”
and “dmirror_do_write” in test_hmm.c
Therefore, replace kmap() with kmap_local_page() and use
mempcy_from/to_page() to avoid open coding kmap_local_page() + memcpy() +
kunmap_local().
Remove the unused variable “tmp”.
Link: https://lkml.kernel.org/r/20230610175712.GA348514@sumitra.com
Signed-off-by: Sumitra Sharma <sumitraartsy@gmail.com>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Cc: Deepak R Varma <drv@mailo.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'lib/test_hmm.c')
| -rw-r--r-- | lib/test_hmm.c | 10 |
1 files changed, 2 insertions, 8 deletions
diff --git a/lib/test_hmm.c b/lib/test_hmm.c index 67e6f83fe0f8..717dcb830127 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -368,16 +368,13 @@ static int dmirror_do_read(struct dmirror *dmirror, unsigned long start, for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) { void *entry; struct page *page; - void *tmp; entry = xa_load(&dmirror->pt, pfn); page = xa_untag_pointer(entry); if (!page) return -ENOENT; - tmp = kmap(page); - memcpy(ptr, tmp, PAGE_SIZE); - kunmap(page); + memcpy_from_page(ptr, page, 0, PAGE_SIZE); ptr += PAGE_SIZE; bounce->cpages++; @@ -437,16 +434,13 @@ static int dmirror_do_write(struct dmirror *dmirror, unsigned long start, for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) { void *entry; struct page *page; - void *tmp; entry = xa_load(&dmirror->pt, pfn); page = xa_untag_pointer(entry); if (!page || xa_pointer_tag(entry) != DPT_XA_TAG_WRITE) return -ENOENT; - tmp = kmap(page); - memcpy(tmp, ptr, PAGE_SIZE); - kunmap(page); + memcpy_to_page(page, 0, ptr, PAGE_SIZE); ptr += PAGE_SIZE; bounce->cpages++; |