Merge patch series "fs/buffer: misc optimizations"

Davidlohr Bueso <dave@stgolabs.net> says:

Four small patches - the first could be sent to Linus for v6.15
considering it is a missing nonblocking lookup conversion in the getblk
slowpath I had missed. The other two patches are small optimizations
found while reading the code, and one rocket science cleanup patch.

* patches from https://lore.kernel.org/20250515173925.147823-1-dave@stgolabs.net:
  fs/buffer: optimize discard_buffer()
  fs/buffer: remove superfluous statements
  fs/buffer: avoid redundant lookup in getblk slowpath
  fs/buffer: use sleeping lookup in __getblk_slowpath()

Link: https://lore.kernel.org/20250515173925.147823-1-dave@stgolabs.net
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: brauner

fs/buffer.c

@@ -297,7 +297,6 @@ static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
 
 still_busy:
 	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
-	return;
 }
 
 struct postprocess_bh_ctx {
@@ -422,7 +421,6 @@ static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
 
 still_busy:
 	spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
-	return;
 }
 
 /*
@@ -1122,6 +1120,8 @@ static struct buffer_head *
 __getblk_slow(struct block_device *bdev, sector_t block,
 	     unsigned size, gfp_t gfp)
 {
+	bool blocking = gfpflags_allow_blocking(gfp);
+
 	/* Size must be multiple of hard sectorsize */
 	if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
 			(size < 512 || size > PAGE_SIZE))) {
@@ -1137,12 +1137,15 @@ __getblk_slow(struct block_device *bdev, sector_t block,
 	for (;;) {
 		struct buffer_head *bh;
 
-		bh = __find_get_block(bdev, block, size);
-		if (bh)
-			return bh;
-
 		if (!grow_buffers(bdev, block, size, gfp))
 			return NULL;
+
+		if (blocking)
+			bh = __find_get_block_nonatomic(bdev, block, size);
+		else
+			bh = __find_get_block(bdev, block, size);
+		if (bh)
+			return bh;
 	}
 }
 
@@ -1611,8 +1614,8 @@ static void discard_buffer(struct buffer_head * bh)
 	bh->b_bdev = NULL;
 	b_state = READ_ONCE(bh->b_state);
 	do {
-	} while (!try_cmpxchg(&bh->b_state, &b_state,
-			      b_state & ~BUFFER_FLAGS_DISCARD));
+	} while (!try_cmpxchg_relaxed(&bh->b_state, &b_state,
+				      b_state & ~BUFFER_FLAGS_DISCARD));
 	unlock_buffer(bh);
 }
 
@@ -1677,7 +1680,6 @@ void block_invalidate_folio(struct folio *folio, size_t offset, size_t length)
 		filemap_release_folio(folio, 0);
 out:
 	folio_clear_mappedtodisk(folio);
-	return;
 }
 EXPORT_SYMBOL(block_invalidate_folio);