iomap: use find_next_bit() for uptodate bitmap scanning

Use find_next_bit()/find_next_zero_bit() for iomap uptodate bitmap
scanning. This uses __ffs() internally and is more efficient for
finding the next uptodate or non-uptodate bit than iterating through the
the bitmap range testing every bit.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://patch.msgid.link/20251111193658.3495942-10-joannelkoong@gmail.com
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 3713ced188abb2124f1ebdb792c5ee2183bcf341..089566a36cff59fb179e07aa64ec155f3070d597 100644 (file)
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -38,10 +38,28 @@ static inline bool ifs_is_fully_uptodate(struct folio *folio,
        return bitmap_full(ifs->state, i_blocks_per_folio(inode, folio));
 }
 
-static inline bool ifs_block_is_uptodate(struct iomap_folio_state *ifs,
-               unsigned int block)
+/*
+ * Find the next uptodate block in the folio. end_blk is inclusive.
+ * If no uptodate block is found, this will return end_blk + 1.
+ */
+static unsigned ifs_next_uptodate_block(struct folio *folio,
+               unsigned start_blk, unsigned end_blk)
 {
-       return test_bit(block, ifs->state);
+       struct iomap_folio_state *ifs = folio->private;
+
+       return find_next_bit(ifs->state, end_blk + 1, start_blk);
+}
+
+/*
+ * Find the next non-uptodate block in the folio. end_blk is inclusive.
+ * If no non-uptodate block is found, this will return end_blk + 1.
+ */
+static unsigned ifs_next_nonuptodate_block(struct folio *folio,
+               unsigned start_blk, unsigned end_blk)
+{
+       struct iomap_folio_state *ifs = folio->private;
+
+       return find_next_zero_bit(ifs->state, end_blk + 1, start_blk);
 }
 
 static bool ifs_set_range_uptodate(struct folio *folio,
@@ -277,14 +295,11 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
         * to avoid reading in already uptodate ranges.
         */
        if (ifs) {
-               unsigned int i, blocks_skipped;
+               unsigned int next, blocks_skipped;
 
-               /* move forward for each leading block marked uptodate */
-               for (i = first; i <= last; i++)
-                       if (!ifs_block_is_uptodate(ifs, i))
-                               break;
+               next = ifs_next_nonuptodate_block(folio, first, last);
+               blocks_skipped = next - first;
 
-               blocks_skipped = i - first;
                if (blocks_skipped) {
                        unsigned long block_offset = *pos & (block_size - 1);
                        unsigned bytes_skipped =
@@ -294,15 +309,15 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
                        poff += bytes_skipped;
                        plen -= bytes_skipped;
                }
-               first = i;
+               first = next;
 
                /* truncate len if we find any trailing uptodate block(s) */
-               while (++i <= last) {
-                       if (ifs_block_is_uptodate(ifs, i)) {
+               if (++next <= last) {
+                       next = ifs_next_uptodate_block(folio, next, last);
+                       if (next <= last) {
                                plen -= iomap_bytes_to_truncate(*pos + plen,
-                                               block_bits, last - i + 1);
-                               last = i - 1;
-                               break;
+                                               block_bits, last - next + 1);
+                               last = next - 1;
                        }
                }
        }
@@ -639,7 +654,7 @@ bool iomap_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
 {
        struct iomap_folio_state *ifs = folio->private;
        struct inode *inode = folio->mapping->host;
-       unsigned first, last, i;
+       unsigned first, last;
 
        if (!ifs)
                return false;
@@ -651,10 +666,7 @@ bool iomap_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
        first = from >> inode->i_blkbits;
        last = (from + count - 1) >> inode->i_blkbits;
 
-       for (i = first; i <= last; i++)
-               if (!ifs_block_is_uptodate(ifs, i))
-                       return false;
-       return true;
+       return ifs_next_nonuptodate_block(folio, first, last) > last;
 }
 EXPORT_SYMBOL_GPL(iomap_is_partially_uptodate);