Messages in this thread | | | From | "Fabio M. De Francesco" <> | Subject | Re: [RFC PATCH v2 2/3] btrfs: Use kmap_local_page() on "out_page" in zlib_compress_pages() | Date | Fri, 17 Jun 2022 19:46:21 +0200 |
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On venerdì 17 giugno 2022 14:54:22 CEST Qu Wenruo wrote: > > 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> >
Again, thanks.
> The change is just to use @cpage_out to indicate if it's mapped (NULL = > not mapped). >
Most of the conversions are quite easy, I would say "mechanical". As you already noted in 3/3, there are cases where it's not that simple :-(
> 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? >
I suppose it's a relic of RFC v1 that I overlooked when I split it into three patches. I will remember to avoid initialization in the "real" patch.
Fabio
> > 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); >
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