| Message ID | 367fe83ae53839b1e88dc00b5b420035496d28ff.1725481503.git.josef@toxicpanda.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | fanotify: add pre-content hooks | expand |
On Wed, Sep 4, 2024 at 10:29 PM Josef Bacik <josef@toxicpanda.com> wrote: > > 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. IIUC, you are disabling the *start* of async defrag. What happens if defrag has already started and then a pre-content watch is set up? Do we care about this corner of a corner case? Thanks, Amir. > > Signed-off-by: Josef Bacik <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 e0a664b8a46a..529f7416814f 100644 > --- a/fs/btrfs/ioctl.c > +++ b/fs/btrfs/ioctl.c > @@ -2640,6 +2640,15 @@ 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; > -- > 2.43.0 >
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index e0a664b8a46a..529f7416814f 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2640,6 +2640,15 @@ 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;
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 <josef@toxicpanda.com> --- fs/btrfs/ioctl.c | 9 +++++++++ 1 file changed, 9 insertions(+)