zram: factor out WB and non-WB zram read functions

We will use non-WB variant in ZRAM page recompression path.

Link: https://lkml.kernel.org/r/20221109115047.2921851-4-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 8ea4908..135fb94 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1336,8 +1336,29 @@ out:
                ~(1UL << ZRAM_LOCK | 1UL << ZRAM_UNDER_WB));
 }
 
-static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
-                               struct bio *bio, bool partial_io)
+/*
+ * Reads a page from the writeback devices. Corresponding ZRAM slot
+ * should be unlocked.
+ */
+static int zram_bvec_read_from_bdev(struct zram *zram, struct page *page,
+                                   u32 index, struct bio *bio, bool partial_io)
+{
+       struct bio_vec bvec = {
+               .bv_page = page,
+               .bv_len = PAGE_SIZE,
+               .bv_offset = 0,
+       };
+
+       return read_from_bdev(zram, &bvec, zram_get_element(zram, index), bio,
+                             partial_io);
+}
+
+/*
+ * Reads (decompresses if needed) a page from zspool (zsmalloc).
+ * Corresponding ZRAM slot should be locked.
+ */
+static int zram_read_from_zspool(struct zram *zram, struct page *page,
+                                u32 index)
 {
        struct zcomp_strm *zstrm;
        unsigned long handle;
@@ -1345,23 +1366,6 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
        void *src, *dst;
        int ret;
 
-       zram_slot_lock(zram, index);
-       if (zram_test_flag(zram, index, ZRAM_WB)) {
-               struct bio_vec bvec;
-
-               zram_slot_unlock(zram, index);
-               /* A null bio means rw_page was used, we must fallback to bio */
-               if (!bio)
-                       return -EOPNOTSUPP;
-
-               bvec.bv_page = page;
-               bvec.bv_len = PAGE_SIZE;
-               bvec.bv_offset = 0;
-               return read_from_bdev(zram, &bvec,
-                               zram_get_element(zram, index),
-                               bio, partial_io);
-       }
-
        handle = zram_get_handle(zram, index);
        if (!handle || zram_test_flag(zram, index, ZRAM_SAME)) {
                unsigned long value;
@@ -1371,7 +1375,6 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
                mem = kmap_atomic(page);
                zram_fill_page(mem, PAGE_SIZE, value);
                kunmap_atomic(mem);
-               zram_slot_unlock(zram, index);
                return 0;
        }
 
@@ -1393,17 +1396,40 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
                zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
        }
        zs_unmap_object(zram->mem_pool, handle);
-       zram_slot_unlock(zram, index);
+       return ret;
+}
+
+static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
+                           struct bio *bio, bool partial_io)
+{
+       int ret;
+
+       zram_slot_lock(zram, index);
+       if (!zram_test_flag(zram, index, ZRAM_WB)) {
+               /* Slot should be locked through out the function call */
+               ret = zram_read_from_zspool(zram, page, index);
+               zram_slot_unlock(zram, index);
+       } else {
+               /* Slot should be unlocked before the function call */
+               zram_slot_unlock(zram, index);
+
+               /* A null bio means rw_page was used, we must fallback to bio */
+               if (!bio)
+                       return -EOPNOTSUPP;
+
+               ret = zram_bvec_read_from_bdev(zram, page, index, bio,
+                                              partial_io);
+       }
 
        /* Should NEVER happen. Return bio error if it does. */
-       if (WARN_ON(ret))
+       if (WARN_ON(ret < 0))
                pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 
        return ret;
 }
 
 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
-                               u32 index, int offset, struct bio *bio)
+                         u32 index, int offset, struct bio *bio)
 {
        int ret;
        struct page *page;