On Fri, Oct 25, 2019 at 02:18:02PM -0500, Eric Sandeen wrote:
> On 10/25/19 12:40 PM, Christoph Hellwig wrote:
> > Fill in the default _log values in xfs_parseargs similar to other
> > defaults, and open code the updates based on the on-disk superblock
> > in xfs_mountfs now that they are completely trivial.
> >
> > Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> > ---
> > fs/xfs/xfs_mount.c | 36 +++++-------------------------------
> > fs/xfs/xfs_super.c | 5 +++++
> > 2 files changed, 10 insertions(+), 31 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> > index 9800401a7d6f..bae53fdd5d51 100644
> > --- a/fs/xfs/xfs_mount.c
> > +++ b/fs/xfs/xfs_mount.c
> > @@ -425,35 +425,6 @@ xfs_update_alignment(xfs_mount_t *mp)
> > return 0;
> > }
> >
> > -/*
> > - * Set the default minimum read and write sizes unless
> > - * already specified in a mount option.
> > - * We use smaller I/O sizes when the file system
> > - * is being used for NFS service (wsync mount option).
> > - */
> > -STATIC void
> > -xfs_set_rw_sizes(xfs_mount_t *mp)
> > -{
> > - xfs_sb_t *sbp = &(mp->m_sb);
> > - int writeio_log;
> > -
> > - if (!(mp->m_flags & XFS_MOUNT_DFLT_IOSIZE)) {
> > - if (mp->m_flags & XFS_MOUNT_WSYNC)
> > - writeio_log = XFS_WRITEIO_LOG_WSYNC;
> > - else
> > - writeio_log = XFS_WRITEIO_LOG_LARGE;
> > - } else {
> > - writeio_log = mp->m_writeio_log;
> > - }
> > -
> > - if (sbp->sb_blocklog > writeio_log) {
> > - mp->m_writeio_log = sbp->sb_blocklog;
> > - } else {
> > - mp->m_writeio_log = writeio_log;
> > - }
> > - mp->m_writeio_blocks = 1 << (mp->m_writeio_log - sbp->sb_blocklog);
> > -}
> > -
> > /*
> > * precalculate the low space thresholds for dynamic speculative preallocation.
> > */
> > @@ -718,9 +689,12 @@ xfs_mountfs(
> > goto out_remove_errortag;
> >
> > /*
> > - * Set the minimum read and write sizes
> > + * Update the preferred write size based on the information from the
> > + * on-disk superblock.
> > */
> > - xfs_set_rw_sizes(mp);
> > + mp->m_writeio_log =
> > + max_t(uint32_t, mp->m_sb.sb_blocklog, mp->m_writeio_log);
> > + mp->m_writeio_blocks = 1 << (mp->m_writeio_log - mp->m_sb.sb_blocklog);
> >
> > /* set the low space thresholds for dynamic preallocation */
> > xfs_set_low_space_thresholds(mp);
> > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> > index 1467f4bebc41..83dbfcc5a02d 100644
> > --- a/fs/xfs/xfs_super.c
> > +++ b/fs/xfs/xfs_super.c
> > @@ -405,6 +405,11 @@ xfs_parseargs(
> > XFS_MIN_IO_LOG, XFS_MAX_IO_LOG);
> > return -EINVAL;
> > }
> > + } else {
> > + if (mp->m_flags & XFS_MOUNT_WSYNC)
> > + mp->m_writeio_log = XFS_WRITEIO_LOG_WSYNC;
> > + else
> > + mp->m_writeio_log = XFS_WRITEIO_LOG_LARGE;
> > }
>
> Ok let's see, by here, if Opt_allocsize was specified, we set
> mp->m_writeio_log to the specified value, else if Opt_wsync was set, we
> set m_writeio_log to XFS_WRITEIO_LOG_WSYNC (14), otherwise we default to
> XFS_WRITEIO_LOG_LARGE (16). So that's it for parseargs.
>
> AFAICT we can't escape parseargs w/ writeio_log less than PAGE_SHIFT
> (i.e. page size).
We can - 64k page size means XFS_WRITEIO_LOG_WSYNC is less than
PAGE_SHIFT, so it can escape here.
> Then in xfs_mountfs, you have it reset to the max of sb_blocklog and
> m_writeio_log. i.e. it gets resized iff sb_blocklog is greater than
> the current m_writeio_log, which has a minimum of page size.
>
> IOWS, it only gets a new value in mountfs if block size is > page size.
Which will never be true on 64k page size machines, but that's not
what this code does, anyway. It will rewrite m_writeio_log if the
block size is larger than the m_writeio_log value, so it preserves
the existing behaviour of setting the m_writeio_log value to a
minimum of one filesystem block....
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
