Patch "fs: create kiocb_{start,end}_write() helpers" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    fs: create kiocb_{start,end}_write() helpers

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fs-create-kiocb_-start-end-_write-helpers.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit d265f96a69a7bafaf9eaaa1ab74bb451734108fb
Author: Amir Goldstein <amir73il@xxxxxxxxx>
Date:   Thu Aug 17 17:13:33 2023 +0300

    fs: create kiocb_{start,end}_write() helpers
    
    Commit ed0360bbab72b829437b67ebb2f9cfac19f59dfe upstream.
    
    aio, io_uring, cachefiles and overlayfs, all open code an ugly variant
    of file_{start,end}_write() to silence lockdep warnings.
    
    Create helpers for this lockdep dance so we can use the helpers in all
    the callers.
    
    Suggested-by: Jan Kara <jack@xxxxxxx>
    Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
    Reviewed-by: Jan Kara <jack@xxxxxxx>
    Reviewed-by: Jens Axboe <axboe@xxxxxxxxx>
    Message-Id: <20230817141337.1025891-4-amir73il@xxxxxxxxx>
    Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/fs.h b/include/linux/fs.h
index a7d839b196069..4e475ded5cf58 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1797,6 +1797,41 @@ static inline bool sb_start_intwrite_trylock(struct super_block *sb)
 	return __sb_start_write_trylock(sb, SB_FREEZE_FS);
 }
 
+/**
+ * kiocb_start_write - get write access to a superblock for async file io
+ * @iocb: the io context we want to submit the write with
+ *
+ * This is a variant of sb_start_write() for async io submission.
+ * Should be matched with a call to kiocb_end_write().
+ */
+static inline void kiocb_start_write(struct kiocb *iocb)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+
+	sb_start_write(inode->i_sb);
+	/*
+	 * Fool lockdep by telling it the lock got released so that it
+	 * doesn't complain about the held lock when we return to userspace.
+	 */
+	__sb_writers_release(inode->i_sb, SB_FREEZE_WRITE);
+}
+
+/**
+ * kiocb_end_write - drop write access to a superblock after async file io
+ * @iocb: the io context we sumbitted the write with
+ *
+ * Should be matched with a call to kiocb_start_write().
+ */
+static inline void kiocb_end_write(struct kiocb *iocb)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+
+	/*
+	 * Tell lockdep we inherited freeze protection from submission thread.
+	 */
+	__sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
+	sb_end_write(inode->i_sb);
+}
 
 extern bool inode_owner_or_capable(const struct inode *inode);