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).
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 is a little surprising and nonobvious and it makes me wonder
if you're intentionally future-proofing here, or if that's just weird.
:)
-Eric
> return 0;
>
