| Message ID | 20220627163305.24116-1-fmdefrancesco@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: Convert zlib_compress_pages() to use kmap_local_page() | expand |
On Mon, Jun 27, 2022 at 06:33:05PM +0200, 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() 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() (thanks to David Sterba). > > 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: David Sterba <dsterba@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> > --- > fs/btrfs/zlib.c | 32 +++++++++++++------------------- > 1 file changed, 13 insertions(+), 19 deletions(-) > > diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c > index 770c4c6bbaef..b4f44662cda7 100644 > --- 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; > } > > -- > 2.36.1 >
On Mon, Jun 27, 2022 at 06:33:05PM +0200, 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() 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() (thanks to David Sterba). > > 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: David Sterba <dsterba@suse.com> > Suggested-by: Ira Weiny <ira.weiny@intel.com> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Added to the kmap patch queue, thanks.
diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c index 770c4c6bbaef..b4f44662cda7 100644 --- 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; }
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() (thanks to David Sterba). 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: David Sterba <dsterba@suse.com> Suggested-by: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> --- fs/btrfs/zlib.c | 32 +++++++++++++------------------- 1 file changed, 13 insertions(+), 19 deletions(-)