On 09/01/2015 03:01 PM, Omar Sandoval wrote:
From: Omar Sandoval <osan...@fb.com>
These are going to be used for the free space tree bitmap items.
Signed-off-by: Omar Sandoval <osan...@fb.com>
Can we get sanity tests for these operations so we know they are
properly unit tested?
---
fs/btrfs/extent_io.c | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/extent_io.h | 6 +++
2 files changed, 107 insertions(+)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 02d05817cbdf..649e3b4eeb1b 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -5475,6 +5475,107 @@ void copy_extent_buffer(struct extent_buffer *dst,
struct extent_buffer *src,
}
}
+/*
+ * The extent buffer bitmap operations are done with byte granularity because
+ * bitmap items are not guaranteed to be aligned to a word and therefore a
+ * single word in a bitmap may straddle two pages in the extent buffer.
+ */
+#define BIT_BYTE(nr) ((nr) / BITS_PER_BYTE)
+#define BYTE_MASK ((1 << BITS_PER_BYTE) - 1)
+#define BITMAP_FIRST_BYTE_MASK(start) \
+ ((BYTE_MASK << ((start) & (BITS_PER_BYTE - 1))) & BYTE_MASK)
+#define BITMAP_LAST_BYTE_MASK(nbits) \
+ (BYTE_MASK >> (-(nbits) & (BITS_PER_BYTE - 1)))
+
+int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start,
+ unsigned long nr)
+{
+ size_t offset;
+ char *kaddr;
+ struct page *page;
+ size_t byte_offset = BIT_BYTE(nr);
+ size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
+ unsigned long i = (start_offset + start + byte_offset) >>
PAGE_CACHE_SHIFT;
+
+ offset = (start_offset + start + byte_offset) & (PAGE_CACHE_SIZE - 1);
+ page = eb->pages[i];
+ WARN_ON(!PageUptodate(page));
+ kaddr = page_address(page);
+ return 1U & (kaddr[offset] >> (nr & (BITS_PER_BYTE - 1)));
+}
+
+void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,
+ unsigned long pos, unsigned long len)
+{
+ size_t offset;
+ char *kaddr;
+ struct page *page;
+ size_t byte_offset = BIT_BYTE(pos);
+ size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
+ unsigned long i = (start_offset + start + byte_offset) >>
PAGE_CACHE_SHIFT;
+ const unsigned int size = pos + len;
+ int bits_to_set = BITS_PER_BYTE - (pos % BITS_PER_BYTE);
+ unsigned int mask_to_set = BITMAP_FIRST_BYTE_MASK(pos);
+
+ offset = (start_offset + start + byte_offset) & (PAGE_CACHE_SIZE - 1);
+ page = eb->pages[i];
+ WARN_ON(!PageUptodate(page));
+ kaddr = page_address(page);
+
+ while (len >= bits_to_set) {
+ kaddr[offset] |= mask_to_set;
+ len -= bits_to_set;
+ bits_to_set = BITS_PER_BYTE;
+ mask_to_set = ~0U;
+ if (++offset >= PAGE_CACHE_SIZE && len > 0) {
+ offset = 0;
+ page = eb->pages[++i];
+ WARN_ON(!PageUptodate(page));
+ kaddr = page_address(page);
+ }
+ }
+ if (len) {
+ mask_to_set &= BITMAP_LAST_BYTE_MASK(size);
+ kaddr[offset] |= mask_to_set;
+ }
+}
+
+void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,
+ unsigned long pos, unsigned long len)
+{
+ size_t offset;
+ char *kaddr;
+ struct page *page;
+ size_t byte_offset = BIT_BYTE(pos);
+ size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
+ unsigned long i = (start_offset + start + byte_offset) >>
PAGE_CACHE_SHIFT;
+ const unsigned int size = pos + len;
+ int bits_to_clear = BITS_PER_BYTE - (pos % BITS_PER_BYTE);
+ unsigned int mask_to_clear = BITMAP_FIRST_BYTE_MASK(pos);
+
+ offset = (start_offset + start + byte_offset) & (PAGE_CACHE_SIZE - 1);
+ page = eb->pages[i];
+ WARN_ON(!PageUptodate(page));
+ kaddr = page_address(page);
+
Abstract this offset finding logic to a helper function and then comment
the hell out of it, I now have a migraine trying to figure out what is
going on. Thanks,
Josef
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