iomap: iterate over folio mapping in iomap_readpage_iter()

Iterate over all non-uptodate ranges of a folio mapping in a single call
to iomap_readpage_iter() instead of leaving the partial iteration to the
caller.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index b06b532033adf8292b80043085d19506fcf679bc..dbe5783ee68c7dc2476f97a6c488614cdde669b4 100644 (file)
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -430,6 +430,7 @@ static int iomap_readpage_iter(struct iomap_iter *iter,
        loff_t length = iomap_length(iter);
        struct folio *folio = ctx->cur_folio;
        size_t poff, plen;
+       loff_t count;
        int ret;
 
        if (iomap->type == IOMAP_INLINE) {
@@ -439,41 +440,35 @@ static int iomap_readpage_iter(struct iomap_iter *iter,
                return iomap_iter_advance(iter, length);
        }
 
-       /* zero post-eof blocks as the page may be mapped */
        ifs_alloc(iter->inode, folio, iter->flags);
-       iomap_adjust_read_range(iter->inode, folio, &pos, length, &poff, &plen);
-       if (plen == 0)
-               goto done;
 
-       if (iomap_block_needs_zeroing(iter, pos)) {
-               folio_zero_range(folio, poff, plen);
-               iomap_set_range_uptodate(folio, poff, plen);
-       } else {
-               iomap_bio_read_folio_range(iter, ctx, pos, plen);
-       }
+       length = min_t(loff_t, length,
+                       folio_size(folio) - offset_in_folio(folio, pos));
+       while (length) {
+               iomap_adjust_read_range(iter->inode, folio, &pos, length, &poff,
+                               &plen);
 
-done:
-       /*
-        * Move the caller beyond our range so that it keeps making progress.
-        * For that, we have to include any leading non-uptodate ranges, but
-        * we can skip trailing ones as they will be handled in the next
-        * iteration.
-        */
-       length = pos - iter->pos + plen;
-       return iomap_iter_advance(iter, length);
-}
+               count = pos - iter->pos + plen;
+               if (WARN_ON_ONCE(count > length))
+                       return -EIO;
 
-static int iomap_read_folio_iter(struct iomap_iter *iter,
-               struct iomap_readpage_ctx *ctx)
-{
-       int ret;
+               if (plen == 0)
+                       return iomap_iter_advance(iter, count);
 
-       while (iomap_length(iter)) {
-               ret = iomap_readpage_iter(iter, ctx);
+               /* zero post-eof blocks as the page may be mapped */
+               if (iomap_block_needs_zeroing(iter, pos)) {
+                       folio_zero_range(folio, poff, plen);
+                       iomap_set_range_uptodate(folio, poff, plen);
+               } else {
+                       iomap_bio_read_folio_range(iter, ctx, pos, plen);
+               }
+
+               ret = iomap_iter_advance(iter, count);
                if (ret)
                        return ret;
+               length -= count;
+               pos = iter->pos;
        }
-
        return 0;
 }
 
@@ -492,7 +487,7 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
        trace_iomap_readpage(iter.inode, 1);
 
        while ((ret = iomap_iter(&iter, ops)) > 0)
-               iter.status = iomap_read_folio_iter(&iter, &ctx);
+               iter.status = iomap_readpage_iter(&iter, &ctx);
 
        iomap_bio_submit_read(&ctx);
 
@@ -522,6 +517,8 @@ static int iomap_readahead_iter(struct iomap_iter *iter,
                }
                if (!ctx->cur_folio) {
                        ctx->cur_folio = readahead_folio(ctx->rac);
+                       if (WARN_ON_ONCE(!ctx->cur_folio))
+                               return -EINVAL;
                        ctx->cur_folio_in_bio = false;
                }
                ret = iomap_readpage_iter(iter, ctx);