btrfs: introduce helpers for subpage uptodate status

Introduce the following functions to handle subpage uptodate status:

- btrfs_subpage_set_uptodate()
- btrfs_subpage_clear_uptodate()
- btrfs_subpage_test_uptodate()
  These helpers can only be called when the page has subpage attached
  and the range is ensured to be inside the page.

- btrfs_page_set_uptodate()
- btrfs_page_clear_uptodate()
- btrfs_page_test_uptodate()
  These helpers can handle both regular sector size and subpage.
  Although caller should still ensure that the range is inside the page.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
index a2a21fa..4e1b187 100644 (file)
--- a/fs/btrfs/subpage.c
+++ b/fs/btrfs/subpage.c
@@ -101,3 +101,116 @@ void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info,
        ASSERT(atomic_read(&subpage->eb_refs));
        atomic_dec(&subpage->eb_refs);
 }
+
+/*
+ * Convert the [start, start + len) range into a u16 bitmap
+ *
+ * For example: if start == page_offset() + 16K, len = 16K, we get 0x00f0.
+ */
+static u16 btrfs_subpage_calc_bitmap(const struct btrfs_fs_info *fs_info,
+               struct page *page, u64 start, u32 len)
+{
+       const int bit_start = offset_in_page(start) >> fs_info->sectorsize_bits;
+       const int nbits = len >> fs_info->sectorsize_bits;
+
+       /* Basic checks */
+       ASSERT(PagePrivate(page) && page->private);
+       ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&
+              IS_ALIGNED(len, fs_info->sectorsize));
+
+       /*
+        * The range check only works for mapped page, we can still have
+        * unmapped page like dummy extent buffer pages.
+        */
+       if (page->mapping)
+               ASSERT(page_offset(page) <= start &&
+                      start + len <= page_offset(page) + PAGE_SIZE);
+       /*
+        * Here nbits can be 16, thus can go beyond u16 range. We make the
+        * first left shift to be calculate in unsigned long (at least u32),
+        * then truncate the result to u16.
+        */
+       return (u16)(((1UL << nbits) - 1) << bit_start);
+}
+
+void btrfs_subpage_set_uptodate(const struct btrfs_fs_info *fs_info,
+               struct page *page, u64 start, u32 len)
+{
+       struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private;
+       const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len);
+       unsigned long flags;
+
+       spin_lock_irqsave(&subpage->lock, flags);
+       subpage->uptodate_bitmap |= tmp;
+       if (subpage->uptodate_bitmap == U16_MAX)
+               SetPageUptodate(page);
+       spin_unlock_irqrestore(&subpage->lock, flags);
+}
+
+void btrfs_subpage_clear_uptodate(const struct btrfs_fs_info *fs_info,
+               struct page *page, u64 start, u32 len)
+{
+       struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private;
+       const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len);
+       unsigned long flags;
+
+       spin_lock_irqsave(&subpage->lock, flags);
+       subpage->uptodate_bitmap &= ~tmp;
+       ClearPageUptodate(page);
+       spin_unlock_irqrestore(&subpage->lock, flags);
+}
+
+/*
+ * Unlike set/clear which is dependent on each page status, for test all bits
+ * are tested in the same way.
+ */
+#define IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(name)                          \
+bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info,    \
+               struct page *page, u64 start, u32 len)                  \
+{                                                                      \
+       struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; \
+       const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); \
+       unsigned long flags;                                            \
+       bool ret;                                                       \
+                                                                       \
+       spin_lock_irqsave(&subpage->lock, flags);                       \
+       ret = ((subpage->name##_bitmap & tmp) == tmp);                  \
+       spin_unlock_irqrestore(&subpage->lock, flags);                  \
+       return ret;                                                     \
+}
+IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(uptodate);
+
+/*
+ * Note that, in selftests (extent-io-tests), we can have empty fs_info passed
+ * in.  We only test sectorsize == PAGE_SIZE cases so far, thus we can fall
+ * back to regular sectorsize branch.
+ */
+#define IMPLEMENT_BTRFS_PAGE_OPS(name, set_page_func, clear_page_func, \
+                              test_page_func)                          \
+void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info,                \
+               struct page *page, u64 start, u32 len)                  \
+{                                                                      \
+       if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) {   \
+               set_page_func(page);                                    \
+               return;                                                 \
+       }                                                               \
+       btrfs_subpage_set_##name(fs_info, page, start, len);            \
+}                                                                      \
+void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info,      \
+               struct page *page, u64 start, u32 len)                  \
+{                                                                      \
+       if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) {   \
+               clear_page_func(page);                                  \
+               return;                                                 \
+       }                                                               \
+       btrfs_subpage_clear_##name(fs_info, page, start, len);          \
+}                                                                      \
+bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info,       \
+               struct page *page, u64 start, u32 len)                  \
+{                                                                      \
+       if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE)     \
+               return test_page_func(page);                            \
+       return btrfs_subpage_test_##name(fs_info, page, start, len);    \
+}
+IMPLEMENT_BTRFS_PAGE_OPS(uptodate, SetPageUptodate, ClearPageUptodate,
+                        PageUptodate);

diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h
index fe51cc2..98d511c 100644 (file)
--- a/fs/btrfs/subpage.h
+++ b/fs/btrfs/subpage.h
@@ -18,6 +18,7 @@
 struct btrfs_subpage {
        /* Common members for both data and metadata pages */
        spinlock_t lock;
+       u16 uptodate_bitmap;
        union {
                /*
                 * Structures only used by metadata
@@ -51,4 +52,30 @@ void btrfs_page_inc_eb_refs(const struct btrfs_fs_info *fs_info,
 void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info,
                            struct page *page);
 
+/*
+ * Template for subpage related operations.
+ *
+ * btrfs_subpage_*() are for call sites where the page has subpage attached and
+ * the range is ensured to be inside the page.
+ *
+ * btrfs_page_*() are for call sites where the page can either be subpage
+ * specific or regular page. The function will handle both cases.
+ * But the range still needs to be inside the page.
+ */
+#define DECLARE_BTRFS_SUBPAGE_OPS(name)                                        \
+void btrfs_subpage_set_##name(const struct btrfs_fs_info *fs_info,     \
+               struct page *page, u64 start, u32 len);                 \
+void btrfs_subpage_clear_##name(const struct btrfs_fs_info *fs_info,   \
+               struct page *page, u64 start, u32 len);                 \
+bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info,    \
+               struct page *page, u64 start, u32 len);                 \
+void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info,                \
+               struct page *page, u64 start, u32 len);                 \
+void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info,      \
+               struct page *page, u64 start, u32 len);                 \
+bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info,       \
+               struct page *page, u64 start, u32 len);
+
+DECLARE_BTRFS_SUBPAGE_OPS(uptodate);
+
 #endif