From: Filipe Manana <fdman...@suse.com> If we reflink to or from a file opened with O_SYNC/O_DSYNC or to/from a file that has the S_SYNC attribute set, we totally ignore that and do not durably persist the reflink changes. Since a reflink can change the data readable from a file (and mtime/ctime, or a file size), it makes sense to durably persist (fsync) the source and destination files/ranges.
This was previously discussed at: https://lore.kernel.org/linux-btrfs/20200903035225.GJ6090@magnolia/ The recently introduced test case generic/628, from fstests, exercises these scenarios and currently fails without this change. So make sure we fsync the source and destination files/ranges when either of them was opened with O_SYNC/O_DSYNC or has the S_SYNC attribute set, just like XFS already does. Signed-off-by: Filipe Manana <fdman...@suse.com> --- fs/btrfs/reflink.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c index 6746460fd219..598105574d05 100644 --- a/fs/btrfs/reflink.c +++ b/fs/btrfs/reflink.c @@ -834,6 +834,16 @@ static int btrfs_remap_file_range_prep(struct file *file_in, loff_t pos_in, len, remap_flags); } +static bool file_sync_write(struct file *file) +{ + if (file->f_flags & (__O_SYNC | O_DSYNC)) + return true; + if (IS_SYNC(file_inode(file))) + return true; + + return false; +} + loff_t btrfs_remap_file_range(struct file *src_file, loff_t off, struct file *dst_file, loff_t destoff, loff_t len, unsigned int remap_flags) @@ -871,5 +881,19 @@ loff_t btrfs_remap_file_range(struct file *src_file, loff_t off, unlock_two_nondirectories(src_inode, dst_inode); } + /* + * If either the source or the destination file was opened with O_SYNC, + * O_DSYNC or has the S_SYNC attribute, fsync both the destination and + * source files/ranges, so that after a successful return (0) followed + * by a power failure results in the reflinked data to be readable from + * both files/ranges. + */ + if (ret == 0 && (file_sync_write(src_file) || file_sync_write(dst_file))) { + ret = btrfs_sync_file(src_file, off, off + len - 1, 0); + if (ret == 0) + ret = btrfs_sync_file(dst_file, destoff, + destoff + len - 1, 0); + } + return ret < 0 ? ret : len; } -- 2.28.0
