Messages in this thread | | | Date | Fri, 17 Jun 2022 20:54:22 +0800 | Subject | Re: [RFC PATCH v2 2/3] btrfs: Use kmap_local_page() on "out_page" in zlib_compress_pages() | From | Qu Wenruo <> |
| |
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() for "out_page" 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 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>
Looks good to me.
Reviewed-by: Qu Wenruo <wqu@suse.com>
The change is just to use @cpage_out to indicate if it's mapped (NULL = not mapped).
Just a small nit inlined below.
> --- > fs/btrfs/zlib.c | 20 +++++++++++--------- > 1 file changed, 11 insertions(+), 9 deletions(-) > > diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c > index 770c4c6bbaef..c7c69ce4a1a9 100644 > --- a/fs/btrfs/zlib.c > +++ b/fs/btrfs/zlib.c > @@ -97,8 +97,8 @@ 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 *cpage_out; > + char *data_in = NULL;
I didn't see any diff touching @data_in, any idea why it's initialized to NULL?
Thanks, Qu
> + char *cpage_out = NULL; > int nr_pages = 0; > struct page *in_page = NULL; > struct page *out_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 = kmap_local_page(out_page); > pages[0] = out_page; > nr_pages = 1; > > @@ -196,7 +196,8 @@ 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); > + cpage_out = NULL; > if (nr_pages == nr_dest_pages) { > out_page = NULL; > ret = -E2BIG; > @@ -207,7 +208,7 @@ 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; > @@ -234,7 +235,8 @@ 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); > + cpage_out = NULL; > if (nr_pages == nr_dest_pages) { > out_page = NULL; > ret = -E2BIG; > @@ -245,7 +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; > @@ -264,8 +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); > > if (in_page) { > kunmap(in_page);
| |