Re: [PATCH v3 12/14] xfs: Unmap blocks according to forcealign

Darrick J. Wong
2024-08-06T20:14:39Z

On Thu, Aug 01, 2024 at 04:30:55PM +0000, John Garry wrote:
> For when forcealign is enabled, blocks in an inode need to be unmapped
> according to extent alignment, like what is already done for rtvol.
>
> Change variable isrt in __xfs_bunmapi() to a bool, as that is really what
> it is.
>
> Signed-off-by: John Garry <john.g.garry@oracle.com>
> ---
> fs/xfs/libxfs/xfs_bmap.c | 48 +++++++++++++++++++++++++++++-----------
> fs/xfs/xfs_inode.c | 16 ++++++++++++++
> fs/xfs/xfs_inode.h | 2 ++
> 3 files changed, 53 insertions(+), 13 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 0c3df8c71c6d..d6ae344a17fc 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -5409,6 +5409,25 @@ xfs_bmap_del_extent_real(
> return 0;
> }
>
> +static xfs_extlen_t
> +xfs_bunmapi_align(
> + struct xfs_inode *ip,
> + xfs_fsblock_t fsbno,
> + xfs_extlen_t *off)
> +{
> + struct xfs_mount *mp = ip->i_mount;
> +
> + if (XFS_IS_REALTIME_INODE(ip))
> + return xfs_inode_alloc_fsbsize_align(ip, fsbno, off);
> + /*
> + * The agbno for the fsbno is aligned to extsize, but the fsbno itself
> + * is not necessarily aligned (to extsize), so use agbno to determine
> + * mod+offset to the alloc unit boundary.
> + */
> + return xfs_inode_alloc_fsbsize_align(ip, XFS_FSB_TO_AGBNO(mp, fsbno),
> + off);
> +}
> +
> /*
> * Unmap (remove) blocks from a file.
> * If nexts is nonzero then the number of extents to remove is limited to
> @@ -5430,7 +5449,8 @@ __xfs_bunmapi(
> xfs_extnum_t extno; /* extent number in list */
> struct xfs_bmbt_irec got; /* current extent record */
> struct xfs_ifork *ifp; /* inode fork pointer */
> - int isrt; /* freeing in rt area */
> + bool isrt; /* freeing in rt area */
> + bool isforcealign; /* forcealign inode */
> int logflags; /* transaction logging flags */
> xfs_extlen_t mod; /* rt extent offset */
> struct xfs_mount *mp = ip->i_mount;
> @@ -5468,6 +5488,8 @@ __xfs_bunmapi(
> }
> XFS_STATS_INC(mp, xs_blk_unmap);
> isrt = xfs_ifork_is_realtime(ip, whichfork);
> + isforcealign = (whichfork != XFS_ATTR_FORK) &&
> + xfs_inode_has_forcealign(ip);
> end = start + len;
>
> if (!xfs_iext_lookup_extent_before(ip, ifp, &end, &icur, &got)) {
> @@ -5486,6 +5508,8 @@ __xfs_bunmapi(
> extno = 0;
> while (end != (xfs_fileoff_t)-1 && end >= start &&
> (nexts == 0 || extno < nexts)) {
> + xfs_extlen_t off;

I got really confused because I thought this was a file block offset and
only after more digging realized that this is a sometimes dummy
adjustment variable.

> +
> /*
> * Is the found extent after a hole in which end lives?
> * Just back up to the previous extent, if so.
> @@ -5519,18 +5543,18 @@ __xfs_bunmapi(
> if (del.br_startoff + del.br_blockcount > end + 1)
> del.br_blockcount = end + 1 - del.br_startoff;
>
> - if (!isrt || (flags & XFS_BMAPI_REMAP))
> + if ((!isrt && !isforcealign) || (flags & XFS_BMAPI_REMAP))
> goto delete;
>
> - mod = xfs_rtb_to_rtxoff(mp,
> - del.br_startblock + del.br_blockcount);
> + mod = xfs_bunmapi_align(ip,
> + del.br_startblock + del.br_blockcount, &off);
> if (mod) {

Oof. I don't like how this loop body has the rtx adjustment code
inlined into it. We only use the isrt flag for the one test above.
I tried hoisting this into something less gross involving separate
adjustment functions but then you have to pass in so many outer
variables that it becomes a mess.

The best I can come up with for now is:

unsigned int alloc_fsb = xfs_inode_alloc_fsbsize(ip);
/* no more isrt/isforcealign bools */

...

if (alloc_fsb == 1 || (flags & XFS_BMAPI_REMAP))
goto delete;

mod = do_div(del.br_startblock + del.br_blockcount,
alloc_fsb);
if (mod) {

> /*
> - * Realtime extent not lined up at the end.
> + * Not aligned to allocation unit on the end.
> * The extent could have been split into written
> * and unwritten pieces, or we could just be
> * unmapping part of it. But we can't really
> - * get rid of part of a realtime extent.
> + * get rid of part of an extent.
> */
> if (del.br_state == XFS_EXT_UNWRITTEN) {
> /*
> @@ -5554,7 +5578,7 @@ __xfs_bunmapi(
> ASSERT(del.br_state == XFS_EXT_NORM);
> ASSERT(tp->t_blk_res > 0);
> /*
> - * If this spans a realtime extent boundary,
> + * If this spans an extent boundary,
> * chop it back to the start of the one we end at.
> */
> if (del.br_blockcount > mod) {
> @@ -5571,14 +5595,12 @@ __xfs_bunmapi(
> goto nodelete;
> }
>
> - mod = xfs_rtb_to_rtxoff(mp, del.br_startblock);
> + mod = xfs_bunmapi_align(ip, del.br_startblock, &off);
> if (mod) {
> - xfs_extlen_t off = mp->m_sb.sb_rextsize - mod;

mod = do_div(del.br_startblock, alloc_fsb);
if (mod) {
xfs_extlen_t off = alloc_fsb - mod;

At least then you don't need this weird xfs_inode_alloc_fsbsize_align
that passes back two xfs_extlen_t arguments.

--D

> -
> /*
> - * Realtime extent is lined up at the end but not
> - * at the front. We'll get rid of full extents if
> - * we can.
> + * Extent is lined up to the allocation unit at the
> + * end but not at the front. We'll get rid of full
> + * extents if we can.
> */
> if (del.br_blockcount > off) {
> del.br_blockcount -= off;
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index e7fa155fcbde..bb8abf990186 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -3164,3 +3164,19 @@ xfs_is_always_cow_inode(
> {
> return ip->i_mount->m_always_cow && xfs_has_reflink(ip->i_mount);
> }
> +
> +/* Return mod+offset for a blkno to an extent boundary */
> +xfs_extlen_t
> +xfs_inode_alloc_fsbsize_align(
> + struct xfs_inode *ip,
> + xfs_fileoff_t blkno,
> + xfs_extlen_t *off)
> +{
> + xfs_fileoff_t blkno_start = blkno;
> + xfs_fileoff_t blkno_end = blkno;
> +
> + xfs_roundout_to_alloc_fsbsize(ip, &blkno_start, &blkno_end);
> +
> + *off = blkno_end - blkno;
> + return blkno - blkno_start;
> +}
> diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
> index 6dd8055c98b3..7b77797c3943 100644
> --- a/fs/xfs/xfs_inode.h
> +++ b/fs/xfs/xfs_inode.h
> @@ -647,6 +647,8 @@ void xfs_roundout_to_alloc_fsbsize(struct xfs_inode *ip,
> xfs_fileoff_t *start, xfs_fileoff_t *end);
> void xfs_roundin_to_alloc_fsbsize(struct xfs_inode *ip,
> xfs_fileoff_t *start, xfs_fileoff_t *end);
> +xfs_extlen_t xfs_inode_alloc_fsbsize_align(struct xfs_inode *ip,
> + xfs_fileoff_t blkno, xfs_extlen_t *off);
>
> int xfs_icreate_dqalloc(const struct xfs_icreate_args *args,
> struct xfs_dquot **udqpp, struct xfs_dquot **gdqpp,
> --
> 2.31.1
>
>