[PATCH] btrfs: Convert zlib_compress_pages() to use kmap_local_page()

Fabio M. De Francesco
2022-06-18T09:28:05Z

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.

Tested with xfstests on QEMU + KVM 32-bit VM with 4GB of RAM and
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>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---

This patch builds only on top of
"[PATCH] btrfs: zlib: refactor how we prepare the input buffer" by Qu Wenruo".
https://lore.kernel.org/linux-btrfs/d0bfc791b5509df7b9ad44e41ada197d1b3149b3.1655519730.git.wqu@suse.com/

fs/btrfs/zlib.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index 966e17cea981..4496dd30bd71 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -160,7 +160,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
ret = -ENOMEM;
goto out;
}
- cpage_out = kmap(out_page);
+ cpage_out = kmap_local_page(out_page);
pages[0] = out_page;
nr_pages = 1;

@@ -198,9 +198,9 @@ 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);
+ kunmap_local(cpage_out);
if (nr_pages == nr_dest_pages) {
- out_page = NULL;
+ cpage_out = NULL;
ret = -E2BIG;
goto out;
}
@@ -209,7 +209,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
ret = -ENOMEM;
goto out;
}
- cpage_out = kmap(out_page);
+ cpage_out = kmap_local_page(out_page);
pages[nr_pages] = out_page;
nr_pages++;
workspace->strm.avail_out = PAGE_SIZE;
@@ -236,9 +236,9 @@ 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);
+ kunmap_local(cpage_out);
if (nr_pages == nr_dest_pages) {
- out_page = NULL;
+ cpage_out = NULL;
ret = -E2BIG;
goto out;
}
@@ -247,7 +247,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
ret = -ENOMEM;
goto out;
}
- cpage_out = kmap(out_page);
+ cpage_out = kmap_local_page(out_page);
pages[nr_pages] = out_page;
nr_pages++;
workspace->strm.avail_out = PAGE_SIZE;
@@ -266,8 +266,8 @@ 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 (cpage_out)
+ kunmap_local(cpage_out);
return ret;
}

--
2.36.1