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SubjectRe: [RFC PATCH v2 1/3] btrfs: Convert zlib_decompress_bio() to use kmap_local_page()
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On 2022/6/17 20:05, Fabio M. De Francesco wrote:
> The use of kmap() is being deprecated in favor of kmap_local_page(). With
> kmap_local_page(), the mapping is per thread, CPU local and not globally
> visible.
>
> Therefore, use kmap_local_page() / kunmap_local() in zlib_decompress_bio()
> because in this function the mappings are per thread and are not visible
> in other contexts.
>
> Tested with xfstests on QEMU + KVM 32 bits VM with 4GB of RAM and
> HIGHMEM64G enabled. This patch passes 26/26 tests of group "compress".
>
> Suggested-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu
> ---
> fs/btrfs/zlib.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
> index 767a0c6c9694..770c4c6bbaef 100644
> --- a/fs/btrfs/zlib.c
> +++ b/fs/btrfs/zlib.c
> @@ -287,7 +287,7 @@ int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
> unsigned long buf_start;
> struct page **pages_in = cb->compressed_pages;
>
> - data_in = kmap(pages_in[page_in_index]);
> + data_in = kmap_local_page(pages_in[page_in_index]);
> workspace->strm.next_in = data_in;
> workspace->strm.avail_in = min_t(size_t, srclen, PAGE_SIZE);
> workspace->strm.total_in = 0;
> @@ -309,7 +309,7 @@ int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
>
> if (Z_OK != zlib_inflateInit2(&workspace->strm, wbits)) {
> pr_warn("BTRFS: inflateInit failed\n");
> - kunmap(pages_in[page_in_index]);
> + kunmap_local(data_in);
> return -EIO;
> }
> while (workspace->strm.total_in < srclen) {
> @@ -336,13 +336,13 @@ int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
>
> if (workspace->strm.avail_in == 0) {
> unsigned long tmp;
> - kunmap(pages_in[page_in_index]);
> + kunmap_local(data_in);
> page_in_index++;
> if (page_in_index >= total_pages_in) {
> data_in = NULL;
> break;
> }
> - data_in = kmap(pages_in[page_in_index]);
> + data_in = kmap_local_page(pages_in[page_in_index]);
> workspace->strm.next_in = data_in;
> tmp = srclen - workspace->strm.total_in;
> workspace->strm.avail_in = min(tmp, PAGE_SIZE);
> @@ -355,7 +355,7 @@ int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
> done:
> zlib_inflateEnd(&workspace->strm);
> if (data_in)
> - kunmap(pages_in[page_in_index]);
> + kunmap_local(data_in);
> if (!ret)
> zero_fill_bio(cb->orig_bio);
> return ret;

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