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[76.182.20.124]) by smtp.gmail.com with ESMTPSA id 00721157ae682-6ee44075016sm7768367b3.63.2024.11.15.07.31.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Nov 2024 07:31:56 -0800 (PST) From: Josef Bacik To: kernel-team@fb.com, linux-fsdevel@vger.kernel.org, jack@suse.cz, amir73il@gmail.com, brauner@kernel.org, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org Subject: [PATCH v8 18/19] btrfs: disable defrag on pre-content watched files Date: Fri, 15 Nov 2024 10:30:31 -0500 Message-ID: <4cc5bcea13db7904174353d08e85157356282a59.1731684329.git.josef@toxicpanda.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 --- fs/btrfs/ioctl.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index c9302d193187..1e5913f276be 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 (fsnotify_file_has_pre_content_watches(file)) { + ret = -EINVAL; + goto out; + } + if (argp) { if (copy_from_user(&range, argp, sizeof(range))) { ret = -EFAULT;