btrfs: zlib: replace kmap() with kmap_local_page() in zlib_compress_pages()

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_compress_pages()
because in this function the mappings are per thread and are not visible
in other contexts. Furthermore, drop the mappings of "out_page" which is
allocated within zlib_compress_pages() with alloc_page(GFP_NOFS) and use
page_address().

Tested with xfstests on a QEMU + KVM 32-bits VM with 4GB of RAM booting
a kernel with HIGHMEM64G enabled. This patch passes 26/26 tests of group
"compress".

CC: Qu Wenruo <wqu@suse.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index 767a0c6c9694b0474b5208930f56d46079a3d708..82a43ac90387891b3bfb4e82b5e0efd79f5c5399 100644 (file)
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -97,7 +97,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
 {
        struct workspace *workspace = list_entry(ws, struct workspace, list);
        int ret;
-       char *data_in;
+       char *data_in = NULL;
        char *cpage_out;
        int nr_pages = 0;
        struct page *in_page = NULL;
@@ -126,7 +126,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
                ret = -ENOMEM;
                goto out;
        }
-       cpage_out = kmap(out_page);
+       cpage_out = page_address(out_page);
        pages[0] = out_page;
        nr_pages = 1;
 
@@ -148,26 +148,26 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
                                int i;
 
                                for (i = 0; i < in_buf_pages; i++) {
-                                       if (in_page) {
-                                               kunmap(in_page);
+                                       if (data_in) {
+                                               kunmap_local(data_in);
                                                put_page(in_page);
                                        }
                                        in_page = find_get_page(mapping,
                                                                start >> PAGE_SHIFT);
-                                       data_in = kmap(in_page);
+                                       data_in = kmap_local_page(in_page);
                                        memcpy(workspace->buf + i * PAGE_SIZE,
                                               data_in, PAGE_SIZE);
                                        start += PAGE_SIZE;
                                }
                                workspace->strm.next_in = workspace->buf;
                        } else {
-                               if (in_page) {
-                                       kunmap(in_page);
+                               if (data_in) {
+                                       kunmap_local(data_in);
                                        put_page(in_page);
                                }
                                in_page = find_get_page(mapping,
                                                        start >> PAGE_SHIFT);
-                               data_in = kmap(in_page);
+                               data_in = kmap_local_page(in_page);
                                start += PAGE_SIZE;
                                workspace->strm.next_in = data_in;
                        }
@@ -196,9 +196,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
                 * the stream end if required
                 */
                if (workspace->strm.avail_out == 0) {
-                       kunmap(out_page);
                        if (nr_pages == nr_dest_pages) {
-                               out_page = NULL;
                                ret = -E2BIG;
                                goto out;
                        }
@@ -207,7 +205,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
                                ret = -ENOMEM;
                                goto out;
                        }
-                       cpage_out = kmap(out_page);
+                       cpage_out = page_address(out_page);
                        pages[nr_pages] = out_page;
                        nr_pages++;
                        workspace->strm.avail_out = PAGE_SIZE;
@@ -234,9 +232,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
                        goto out;
                } else if (workspace->strm.avail_out == 0) {
                        /* get another page for the stream end */
-                       kunmap(out_page);
                        if (nr_pages == nr_dest_pages) {
-                               out_page = NULL;
                                ret = -E2BIG;
                                goto out;
                        }
@@ -245,7 +241,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
                                ret = -ENOMEM;
                                goto out;
                        }
-                       cpage_out = kmap(out_page);
+                       cpage_out = page_address(out_page);
                        pages[nr_pages] = out_page;
                        nr_pages++;
                        workspace->strm.avail_out = PAGE_SIZE;
@@ -264,13 +260,11 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
        *total_in = workspace->strm.total_in;
 out:
        *out_pages = nr_pages;
-       if (out_page)
-               kunmap(out_page);
-
-       if (in_page) {
-               kunmap(in_page);
+       if (data_in) {
+               kunmap_local(data_in);
                put_page(in_page);
        }
+
        return ret;
 }