Re: Patch "ext4: enforce buffer head state assertion in ext4_da_map_blocks" has been added to the 5.10-stable tree

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

    ext4: enforce buffer head state assertion in ext4_da_map_blocks

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:
     ext4-enforce-buffer-head-state-assertion-in-ext4_da_.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 [off-list ref] know about it.



commit 38c3015b3b8b3a977ca7fa0da8de65c9d8cab2d2
Author: Eric Whitney [off-list ref]
Date:   Thu Aug 19 10:49:27 2021 -0400

    ext4: enforce buffer head state assertion in ext4_da_map_blocks
    
    [ Upstream commit 948ca5f30e1df0c11eb5b0f410b9ceb97fa77ad9 ]
    
    Remove the code that re-initializes a buffer head with an invalid block
    number and BH_New and BH_Delay bits when a matching delayed and
    unwritten block has been found in the extent status cache. Replace it
    with assertions that verify the buffer head already has this state
    correctly set.  The current code masked an inline data truncation bug
    that left stale entries in the extent status cache.  With this change,
    generic/130 can be used to reproduce and detect that bug.
    
    Signed-off-by: Eric Whitney [off-list ref]
    Signed-off-by: Theodore Ts'o [off-list ref]
    Link: https://lore.kernel.org/r/20210819144927.25163-3-enwlinux@gmail.com (local)
    Signed-off-by: Theodore Ts'o [off-list ref]
    Signed-off-by: Sasha Levin [off-list ref]

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 317aa1b90fb9..fce4fccb8641 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c

@@ -1727,13 +1727,16 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
 		}
 
 		/*
-		 * Delayed extent could be allocated by fallocate.
-		 * So we need to check it.
+		 * the buffer head associated with a delayed and not unwritten
+		 * block found in the extent status cache must contain an
+		 * invalid block number and have its BH_New and BH_Delay bits
+		 * set, reflecting the state assigned when the block was
+		 * initially delayed allocated
 		 */
-		if (ext4_es_is_delayed(&es) && !ext4_es_is_unwritten(&es)) {
-			map_bh(bh, inode->i_sb, invalid_block);
-			set_buffer_new(bh);
-			set_buffer_delay(bh);
+		if (ext4_es_is_delonly(&es)) {
+			BUG_ON(bh->b_blocknr != invalid_block);
+			BUG_ON(!buffer_new(bh));
+			BUG_ON(!buffer_delay(bh));
 			return 0;
 		}