From 080ecbd05432970a8df1f70586b925a18b5ea6f4 Mon Sep 17 00:00:00 2001 From: Robbie Ko Date: Fri, 8 May 2026 21:42:11 +0800 Subject: [PATCH] btrfs: mark file extent range dirty after converting prealloc extents When writing into a preallocated extent, ordered extent completion calls btrfs_mark_extent_written() to convert the file extent item from the BTRFS_FILE_EXTENT_PREALLOC type to the BTRFS_FILE_EXTENT_REG type. If the preallocated extent was created beyond i_size with fallocate keep-size, and the inode is evicted and loaded again before the write, the inode's file_extent_tree is initialized only up to i_size. The beyond i_size prealloc extent is therefore not tracked there. After a write into that extent extends i_size, btrfs_mark_extent_written() updates the file extent item, but the corresponding range is not marked dirty in the inode's file_extent_tree. This can leave disk_i_size stale when the filesystem does not use the no-holes feature, so after remount the file size can go back to the old value. The following reproducer triggers the problem: $ cat test.sh #!/bin/bash DEV=/dev/sdi MNT=/mnt/sdi mkfs.btrfs -f -O ^no-holes $DEV mount $DEV $MNT touch $MNT/file fallocate -n -l 2M $MNT/file umount $MNT mount $DEV $MNT dd if=/dev/zero of=$MNT/file bs=1M count=1 conv=notrunc ls -lh $MNT/file umount $MNT mount $DEV $MNT ls -lh $MNT/file umount $MNT Running the reproducer gives the following result: $ ./test.sh (...) 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.000596024 s, 1.8 GB/s -rw-rw-r-- 1 root root 1.0M May 8 16:34 /mnt/sdi/file -rw-rw-r-- 1 root root 0 May 8 16:34 /mnt/sdi/file Fix this by marking the written range dirty in the inode's file_extent_tree after successfully converting the prealloc extent to a regular extent. Fixes: 9ddc959e802b ("btrfs: use the file extent tree infrastructure") Reviewed-by: Filipe Manana Signed-off-by: Robbie Ko [ Minor change log updates ] Signed-off-by: Filipe Manana Signed-off-by: David Sterba --- fs/btrfs/file.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index cf1cb5c4db75..8c171ed07008 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -633,7 +633,7 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans, trans->transid); btrfs_set_file_extent_num_bytes(leaf, fi, end - other_start); - return 0; + goto mark_dirty; } } @@ -661,7 +661,7 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans, other_end - start); btrfs_set_file_extent_offset(leaf, fi, start - orig_offset); - return 0; + goto mark_dirty; } } @@ -788,7 +788,12 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans, } } - return 0; +mark_dirty: + ret = btrfs_inode_set_file_extent_range(inode, start, end - start); + if (ret) + btrfs_abort_transaction(trans, ret); + + return ret; } /*