linux-ext4 - [PATCH v4 1/7] ext4: Document an edge case for overwrites

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Message-ID: <fd50ba05440042dff77d555e463a620a79f8d0e9.1747289779.git.ritesh.list@gmail.com>
Date: Thu, 15 May 2025 20:15:33 +0530
From: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
To: linux-ext4@...r.kernel.org
Cc: Theodore Ts'o <tytso@....edu>,
	Jan Kara <jack@...e.cz>,
	John Garry <john.g.garry@...cle.com>,
	djwong@...nel.org,
	Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
	linux-fsdevel@...r.kernel.org,
	"Ritesh Harjani (IBM)" <ritesh.list@...il.com>
Subject: [PATCH v4 1/7] ext4: Document an edge case for overwrites

ext4_iomap_overwrite_begin() clears the flag for IOMAP_WRITE before
calling ext4_iomap_begin(). Document this above ext4_map_blocks() call
as it is easy to miss it when focusing on write paths alone.

Reviewed-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Acked-by: Darrick J. Wong <djwong@...nel.org>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
---
 fs/ext4/inode.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 94c7d2d828a6..b10e5cd5bb5c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3436,6 +3436,10 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 		}
 		ret = ext4_iomap_alloc(inode, &map, flags);
 	} else {
+		/*
+		 * This can be called for overwrites path from
+		 * ext4_iomap_overwrite_begin().
+		 */
 		ret = ext4_map_blocks(NULL, inode, &map, 0);
 	}
 
-- 
2.49.0