On Sat, Jan 29, 2022 at 08:59:40PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> If the caller wanted us to persist the preallocation to disk before
> returning to userspace, make sure we force the log to disk after making
> all metadata updates.
>
> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> ---
> fs/xfs/xfs_file.c | 32 +++++++++++++++++++++++++-------
> 1 file changed, 25 insertions(+), 7 deletions(-)
>
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index a54a38e66744..8f2372b96fc4 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -929,6 +929,7 @@ xfs_file_fallocate(
> uint iolock = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
> loff_t new_size = 0;
> bool do_file_insert = false;
> + bool flush_log;
>
> if (!S_ISREG(inode->i_mode))
> return -EINVAL;
> @@ -1078,16 +1079,19 @@ xfs_file_fallocate(
> goto out_unlock;
>
> /*
> - * If we need to change the PREALLOC flag or flush the log, do so.
> - * We already updated the timestamps and cleared the suid flags, so we
> - * don't need to do that again. This must be committed before the size
> - * change so that we don't trim post-EOF preallocations.
> + * If we need to change the PREALLOC flag, do so. We already updated
> + * the timestamps and cleared the suid flags, so we don't need to do
> + * that again. This must be committed before the size change so that
> + * we don't trim post-EOF preallocations. If this is the last
> + * transaction we're going to make, make the update synchronous too.
> */
> - if (xfs_file_sync_writes(file))
> - flags |= XFS_PREALLOC_SYNC;
> + flush_log = xfs_file_sync_writes(file);
> if (flags) {
> flags |= XFS_PREALLOC_INVISIBLE;
>
> + if (flush_log && !(do_file_insert || new_size))
> + flags |= XFS_PREALLOC_SYNC;
> +
> error = xfs_update_prealloc_flags(ip, flags);
> if (error)
> goto out_unlock;
> @@ -1111,8 +1115,22 @@ xfs_file_fallocate(
> * leave shifted extents past EOF and hence losing access to
> * the data that is contained within them.
> */
> - if (do_file_insert)
> + if (do_file_insert) {
> error = xfs_insert_file_space(ip, offset, len);
> + if (error)
> + goto out_unlock;
> + }
> +
> + /*
> + * If the caller wants us to flush the log and either we've made
> + * changes since updating the PREALLOC flag or we didn't need to
> + * update the PREALLOC flag, then flush the log now.
> + */
> + if (flush_log && (do_file_insert || new_size || flags == 0)) {
> + error = xfs_log_force_inode(ip);
> + if (error)
> + goto out_unlock;
> + }
That's pretty crazy. We don't need to do synchronous transactions
for every operation in fallocate(), just guarantee that the
transactions have hit stable storage before we return to userspace.
Hence we don't need to pass SYNC flags anywhere or have stuff like
xfs_update_prealloc_flags() even have to support sync transactions.
All we need is this:
if (xfs_file_sync_writes(file))
error = xfs_log_force_inode(ip);
And that will force out all the changes to the journal at the end
of fallocate if required.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
