Re: [PATCH v3 11/35] iomap: allow filesystem to read fsverity metadata beyound EOF

[Christoph Hellwig <hch@lst.de>]

On Wed, Feb 18, 2026 at 12:19:11AM +0100, Andrey Albershteyn wrote:
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index bd3ab4e6b2bf..6ebf68fdc386 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -533,18 +533,45 @@ static int iomap_read_folio_iter(struct iomap_iter *iter,

I've looked at the modifications to iomap_read_folio_iter over the entire
series.  First comment is that it probably makes sense to have one patch
modifying this logic instead of multiple.  I also think the final result
can be improved quite a bit by a better code structure, see the patch
below against your full series.  I've left three XXX comments with
questions that are probably easier to ask there in the code then
separately, I hope this works for you.

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 9468c5d60b23..48c572d549aa 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -534,47 +534,53 @@ static int iomap_read_folio_iter(struct iomap_iter *iter,
 			return 0;
 
 		/*
-		 * We hits this for two case:
-		 * 1. No need to go further, the hole after fsverity descriptor
-		 * is the end of the fsverity metadata. No ctx->vi means we are
-		 * reading folio with descriptor.
-		 * 2. This folio contains merkle tree blocks which need to be
-		 * synthesized and fsverity descriptor. Skip these blocks as we
-		 * don't know how to synthesize them yet.
+		 * Handling of fsverity "holes". We hits this for two case:
+		 *   1. No need to go further, the hole after fsverity
+		 *	descriptor is the end of the fsverity metadata.
+		 *
+		 *	No ctx->vi means we are reading a folio with descriptor.
+		 *	XXX: what does descriptor mean here?  Also how do we
+		 *	even end up with this case?  I can't see how this can
+		 *	happe based on the caller?
+		 *
+		 *   2. This folio contains merkle tree blocks which need to be
+		 *	synthesized and fsverity descriptor.
 		 */
 		if ((iomap->flags & IOMAP_F_FSVERITY) &&
-		    (iomap->type == IOMAP_HOLE) &&
-		    !(ctx->vi)) {
-			iomap_set_range_uptodate(folio, poff, plen);
-			return iomap_iter_advance(iter, plen);
-		}
+		    iomap->type == IOMAP_HOLE) {
+		    	if (!ctx->vi) {
+				iomap_set_range_uptodate(folio, poff, plen);
+				/*
+				 * XXX: why return to the caller early here?
+				 */
+				return iomap_iter_advance(iter, plen);
+			}
 
-		/* zero post-eof blocks as the page may be mapped */
-		if (iomap_block_needs_zeroing(iter, pos) &&
-		    !(iomap->flags & IOMAP_F_FSVERITY)) {
+			/*
+			 * Synthesize the hash value for a zeroed folio if we
+			 * are reading merkle tree blocks.
+			 */
+			fsverity_folio_zero_hash(folio, poff, plen, ctx->vi);
+			iomap_set_range_uptodate(folio, poff, plen);
+		} else if (iomap_block_needs_zeroing(iter, pos) &&
+			   /*
+			    * XXX: do we still need the IOMAP_F_FSVERITY check
+			    * here, or is this all covered by the above one?
+			    */
+			   !(iomap->flags & IOMAP_F_FSVERITY)) {
+			/* zero post-eof blocks as the page may be mapped */
 			folio_zero_range(folio, poff, plen);
 			if (fsverity_active(iter->inode) &&
 			    !fsverity_verify_blocks(ctx->vi, folio, plen, poff))
 				return -EIO;
 			iomap_set_range_uptodate(folio, poff, plen);
 		} else {
-			/*
-			 * Synthesize zero hash folio if we are reading merkle
-			 * tree blocks
-			 */
-			if ((iomap->flags & IOMAP_F_FSVERITY) &&
-			    (iomap->type == IOMAP_HOLE)) {
-				fsverity_folio_zero_hash(folio, poff, plen,
-							 ctx->vi);
-				iomap_set_range_uptodate(folio, poff, plen);
-			} else {
-				if (!*bytes_submitted)
-					iomap_read_init(folio);
-				ret = ctx->ops->read_folio_range(iter, ctx, plen);
-				if (ret)
-					return ret;
-				*bytes_submitted += plen;
-			}
+			if (!*bytes_submitted)
+				iomap_read_init(folio);
+			ret = ctx->ops->read_folio_range(iter, ctx, plen);
+			if (ret)
+				return ret;
+			*bytes_submitted += plen;
 		}
 
 		ret = iomap_iter_advance(iter, plen);