linux-ext4 - [PATCH 09/10] fuse: overlay iomap inode info in struct fuse

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Message-ID: <176169812272.1426649.9645304318968023284.stgit@frogsfrogsfrogs>
Date: Tue, 28 Oct 2025 17:58:31 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: djwong@...nel.org, miklos@...redi.hu
Cc: joannelkoong@...il.com, bernd@...ernd.com, neal@...pa.dev,
 linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH 09/10] fuse: overlay iomap inode info in struct fuse_inode

From: Darrick J. Wong <djwong@...nel.org>

It's not possible for a regular file to use iomap mode and writeback
caching at the same time, so we can save some memory in struct
fuse_inode by overlaying them in the union.  This is a separate patch
because C unions are rather unsafe and I prefer any errors to be
bisectable to this patch.

Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
 fs/fuse/fuse_i.h |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 03fecb3286c29e..0f49edaf951a6d 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -199,8 +199,11 @@ struct fuse_inode {

 			/* waitq for direct-io completion */
 			wait_queue_head_t direct_io_waitq;
+		};

 #ifdef CONFIG_FUSE_IOMAP
+		/* regular file iomap mode */
+		struct {
 			/* pending io completions */
 			spinlock_t ioend_lock;
 			struct work_struct ioend_work;
@@ -208,8 +211,8 @@ struct fuse_inode {

 			/* cached iomap mappings */
 			struct fuse_iomap_cache cache;
-#endif
 		};
+#endif

 		/* readdir cache (directory only) */
 		struct {