From b722e40be2bda7a688f74e1a794121e84f717fdc Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Fri, 15 Nov 2024 10:30:31 -0500 Subject: [PATCH] btrfs: disable defrag on pre-content watched files We queue up inodes to be defrag'ed asynchronously, which means we do not have their original file for readahead. This means that the code to skip readahead on pre-content watched files will not run, and we could potentially read in empty pages. Handle this corner case by disabling defrag on files that are currently being watched for pre-content events. Signed-off-by: Josef Bacik Signed-off-by: Jan Kara Link: https://patch.msgid.link/4cc5bcea13db7904174353d08e85157356282a59.1731684329.git.josef@toxicpanda.com --- fs/btrfs/ioctl.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index c9302d1931870..51b439537049c 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2635,6 +2635,15 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp) goto out; } + /* + * Don't allow defrag on pre-content watched files, as it could + * populate the page cache with 0's via readahead. + */ + if (unlikely(FMODE_FSNOTIFY_HSM(file->f_mode))) { + ret = -EINVAL; + goto out; + } + if (argp) { if (copy_from_user(&range, argp, sizeof(range))) { ret = -EFAULT; -- 2.39.5