btrfs: zstd: replace kmap() with kmap_local_page()

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 zstd.c because in this
file the mappings are per thread and are not visible in other contexts. In
the meanwhile use plain page_address() on output pages allocated with
the GFP_NOFS flag instead of calling kmap*() on them (since they are
always allocated from ZONE_NORMAL).

Tested with xfstests on QEMU + KVM 32 bits VM with 4GB of RAM, booting a
kernel with HIGHMEM64G enabled.

Suggested-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/zstd.c b/fs/btrfs/zstd.c
index 0fe31a6..35a0224 100644 (file)
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -403,7 +403,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 
        /* map in the first page of input data */
        in_page = find_get_page(mapping, start >> PAGE_SHIFT);
-       workspace->in_buf.src = kmap(in_page);
+       workspace->in_buf.src = kmap_local_page(in_page);
        workspace->in_buf.pos = 0;
        workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
 
@@ -415,7 +415,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
                goto out;
        }
        pages[nr_pages++] = out_page;
-       workspace->out_buf.dst = kmap(out_page);
+       workspace->out_buf.dst = page_address(out_page);
        workspace->out_buf.pos = 0;
        workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
 
@@ -450,9 +450,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
                if (workspace->out_buf.pos == workspace->out_buf.size) {
                        tot_out += PAGE_SIZE;
                        max_out -= PAGE_SIZE;
-                       kunmap(out_page);
                        if (nr_pages == nr_dest_pages) {
-                               out_page = NULL;
                                ret = -E2BIG;
                                goto out;
                        }
@@ -462,7 +460,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
                                goto out;
                        }
                        pages[nr_pages++] = out_page;
-                       workspace->out_buf.dst = kmap(out_page);
+                       workspace->out_buf.dst = page_address(out_page);
                        workspace->out_buf.pos = 0;
                        workspace->out_buf.size = min_t(size_t, max_out,
                                                        PAGE_SIZE);
@@ -477,13 +475,12 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
                /* Check if we need more input */
                if (workspace->in_buf.pos == workspace->in_buf.size) {
                        tot_in += PAGE_SIZE;
-                       kunmap(in_page);
+                       kunmap_local(workspace->in_buf.src);
                        put_page(in_page);
-
                        start += PAGE_SIZE;
                        len -= PAGE_SIZE;
                        in_page = find_get_page(mapping, start >> PAGE_SHIFT);
-                       workspace->in_buf.src = kmap(in_page);
+                       workspace->in_buf.src = kmap_local_page(in_page);
                        workspace->in_buf.pos = 0;
                        workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
                }
@@ -510,9 +507,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 
                tot_out += PAGE_SIZE;
                max_out -= PAGE_SIZE;
-               kunmap(out_page);
                if (nr_pages == nr_dest_pages) {
-                       out_page = NULL;
                        ret = -E2BIG;
                        goto out;
                }
@@ -522,7 +517,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
                        goto out;
                }
                pages[nr_pages++] = out_page;
-               workspace->out_buf.dst = kmap(out_page);
+               workspace->out_buf.dst = page_address(out_page);
                workspace->out_buf.pos = 0;
                workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
        }
@@ -537,13 +532,10 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
        *total_out = tot_out;
 out:
        *out_pages = nr_pages;
-       /* Cleanup */
-       if (in_page) {
-               kunmap(in_page);
+       if (workspace->in_buf.src) {
+               kunmap_local(workspace->in_buf.src);
                put_page(in_page);
        }
-       if (out_page)
-               kunmap(out_page);
        return ret;
 }
 
@@ -567,7 +559,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
                goto done;
        }
 
-       workspace->in_buf.src = kmap(pages_in[page_in_index]);
+       workspace->in_buf.src = kmap_local_page(pages_in[page_in_index]);
        workspace->in_buf.pos = 0;
        workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
 
@@ -603,14 +595,15 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
                        break;
 
                if (workspace->in_buf.pos == workspace->in_buf.size) {
-                       kunmap(pages_in[page_in_index++]);
+                       kunmap_local(workspace->in_buf.src);
+                       page_in_index++;
                        if (page_in_index >= total_pages_in) {
                                workspace->in_buf.src = NULL;
                                ret = -EIO;
                                goto done;
                        }
                        srclen -= PAGE_SIZE;
-                       workspace->in_buf.src = kmap(pages_in[page_in_index]);
+                       workspace->in_buf.src = kmap_local_page(pages_in[page_in_index]);
                        workspace->in_buf.pos = 0;
                        workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
                }
@@ -619,7 +612,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
        zero_fill_bio(cb->orig_bio);
 done:
        if (workspace->in_buf.src)
-               kunmap(pages_in[page_in_index]);
+               kunmap_local(workspace->in_buf.src);
        return ret;
 }