btrfs: switch compression callbacks to direct calls

The indirect calls bring some overhead due to spectre vulnerability
mitigations. The number of cases is small and below the threshold
(10-20) where indirect call would be better.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 8611a8b..87bac8f 100644 (file)
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -86,6 +86,70 @@ bool btrfs_compress_is_valid_type(const char *str, size_t len)
        return false;
 }
 
+static int compression_compress_pages(int type, struct list_head *ws,
+               struct address_space *mapping, u64 start, struct page **pages,
+               unsigned long *out_pages, unsigned long *total_in,
+               unsigned long *total_out)
+{
+       switch (type) {
+       case BTRFS_COMPRESS_ZLIB:
+               return zlib_compress_pages(ws, mapping, start, pages,
+                               out_pages, total_in, total_out);
+       case BTRFS_COMPRESS_LZO:
+               return lzo_compress_pages(ws, mapping, start, pages,
+                               out_pages, total_in, total_out);
+       case BTRFS_COMPRESS_ZSTD:
+               return zstd_compress_pages(ws, mapping, start, pages,
+                               out_pages, total_in, total_out);
+       case BTRFS_COMPRESS_NONE:
+       default:
+               /*
+                * This can't happen, the type is validated several times
+                * before we get here. As a sane fallback, return what the
+                * callers will understand as 'no compression happened'.
+                */
+               return -E2BIG;
+       }
+}
+
+static int compression_decompress_bio(int type, struct list_head *ws,
+               struct compressed_bio *cb)
+{
+       switch (type) {
+       case BTRFS_COMPRESS_ZLIB: return zlib_decompress_bio(ws, cb);
+       case BTRFS_COMPRESS_LZO:  return lzo_decompress_bio(ws, cb);
+       case BTRFS_COMPRESS_ZSTD: return zstd_decompress_bio(ws, cb);
+       case BTRFS_COMPRESS_NONE:
+       default:
+               /*
+                * This can't happen, the type is validated several times
+                * before we get here.
+                */
+               BUG();
+       }
+}
+
+static int compression_decompress(int type, struct list_head *ws,
+               unsigned char *data_in, struct page *dest_page,
+               unsigned long start_byte, size_t srclen, size_t destlen)
+{
+       switch (type) {
+       case BTRFS_COMPRESS_ZLIB: return zlib_decompress(ws, data_in, dest_page,
+                                               start_byte, srclen, destlen);
+       case BTRFS_COMPRESS_LZO:  return lzo_decompress(ws, data_in, dest_page,
+                                               start_byte, srclen, destlen);
+       case BTRFS_COMPRESS_ZSTD: return zstd_decompress(ws, data_in, dest_page,
+                                               start_byte, srclen, destlen);
+       case BTRFS_COMPRESS_NONE:
+       default:
+               /*
+                * This can't happen, the type is validated several times
+                * before we get here.
+                */
+               BUG();
+       }
+}
+
 static int btrfs_decompress_bio(struct compressed_bio *cb);
 
 static inline int compressed_bio_size(struct btrfs_fs_info *fs_info,
@@ -1074,10 +1138,8 @@ int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
 
        level = btrfs_compress_set_level(type, level);
        workspace = get_workspace(type, level);
-       ret = btrfs_compress_op[type]->compress_pages(workspace, mapping,
-                                                     start, pages,
-                                                     out_pages,
-                                                     total_in, total_out);
+       ret = compression_compress_pages(type, workspace, mapping, start, pages,
+                                        out_pages, total_in, total_out);
        put_workspace(type, workspace);
        return ret;
 }
@@ -1103,7 +1165,7 @@ static int btrfs_decompress_bio(struct compressed_bio *cb)
        int type = cb->compress_type;
 
        workspace = get_workspace(type, 0);
-       ret = btrfs_compress_op[type]->decompress_bio(workspace, cb);
+       ret = compression_decompress_bio(type, workspace, cb);
        put_workspace(type, workspace);
 
        return ret;
@@ -1121,9 +1183,8 @@ int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
        int ret;
 
        workspace = get_workspace(type, 0);
-       ret = btrfs_compress_op[type]->decompress(workspace, data_in,
-                                                 dest_page, start_byte,
-                                                 srclen, destlen);
+       ret = compression_decompress(type, workspace, data_in, dest_page,
+                                    start_byte, srclen, destlen);
        put_workspace(type, workspace);
 
        return ret;

diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index 52dce11..7db14d3 100644 (file)
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -140,23 +140,6 @@ struct btrfs_compress_op {
 
        void (*free_workspace)(struct list_head *workspace);
 
-       int (*compress_pages)(struct list_head *workspace,
-                             struct address_space *mapping,
-                             u64 start,
-                             struct page **pages,
-                             unsigned long *out_pages,
-                             unsigned long *total_in,
-                             unsigned long *total_out);
-
-       int (*decompress_bio)(struct list_head *workspace,
-                               struct compressed_bio *cb);
-
-       int (*decompress)(struct list_head *workspace,
-                         unsigned char *data_in,
-                         struct page *dest_page,
-                         unsigned long start_byte,
-                         size_t srclen, size_t destlen);
-
        /* Maximum level supported by the compression algorithm */
        unsigned int max_level;
        unsigned int default_level;

diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c
index 04a6815..9417944 100644 (file)
--- a/fs/btrfs/lzo.c
+++ b/fs/btrfs/lzo.c
@@ -509,9 +509,6 @@ const struct btrfs_compress_op btrfs_lzo_compress = {
        .put_workspace          = lzo_put_workspace,
        .alloc_workspace        = lzo_alloc_workspace,
        .free_workspace         = lzo_free_workspace,
-       .compress_pages         = lzo_compress_pages,
-       .decompress_bio         = lzo_decompress_bio,
-       .decompress             = lzo_decompress,
        .max_level              = 1,
        .default_level          = 1,
 };

diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index 4091f94..8bb6f19 100644 (file)
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -420,9 +420,6 @@ const struct btrfs_compress_op btrfs_zlib_compress = {
        .put_workspace          = zlib_put_workspace,
        .alloc_workspace        = zlib_alloc_workspace,
        .free_workspace         = zlib_free_workspace,
-       .compress_pages         = zlib_compress_pages,
-       .decompress_bio         = zlib_decompress_bio,
-       .decompress             = zlib_decompress,
        .max_level              = 9,
        .default_level          = BTRFS_ZLIB_DEFAULT_LEVEL,
 };

diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index b372822..5f17c74 100644 (file)
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -713,9 +713,6 @@ const struct btrfs_compress_op btrfs_zstd_compress = {
        .put_workspace = zstd_put_workspace,
        .alloc_workspace = zstd_alloc_workspace,
        .free_workspace = zstd_free_workspace,
-       .compress_pages = zstd_compress_pages,
-       .decompress_bio = zstd_decompress_bio,
-       .decompress = zstd_decompress,
        .max_level      = ZSTD_BTRFS_MAX_LEVEL,
        .default_level  = ZSTD_BTRFS_DEFAULT_LEVEL,
 };