[PATCH 01/20] xfs: xfs_alloc_fix_freelist() can use incore perag structures

Dave Chinner
2015-06-03T06:05:19Z

At the moment, xfs_alloc_fix_freelist() uses a mix of per-ag based
access and agf buffer based access to freelist and space usage
information. However, once the AGF buffer is locked inside this
function, it is guaranteed that both the in-memory and on-disk
values are identical. xfs_alloc_fix_freelist() doesn't modify the
values in the structures directly, so it is a read-only user of the
infomration, and hence can use the per-ag structure exclusively for
determining what it should do.

This opens up an avenue for cleaning up a lot of duplicated logic
whose only difference is the structure it gets the data from, and in
doing so removes a lot of needless byte swapping overhead when
fixing up the free list.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/libxfs/xfs_alloc.c | 69 +++++++++++++++++++++--------------------------
fs/xfs/libxfs/xfs_alloc.h | 8 ++----
fs/xfs/libxfs/xfs_bmap.c | 3 ++-
fs/xfs/xfs_filestream.c | 3 ++-
4 files changed, 37 insertions(+), 46 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index bc78ac0..08b45f8 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -1857,11 +1857,11 @@ xfs_alloc_compute_maxlevels(
xfs_extlen_t
xfs_alloc_longest_free_extent(
struct xfs_mount *mp,
- struct xfs_perag *pag)
+ struct xfs_perag *pag,
+ xfs_extlen_t need)
{
- xfs_extlen_t need, delta = 0;
+ xfs_extlen_t delta = 0;

- need = XFS_MIN_FREELIST_PAG(pag, mp);
if (need > pag->pagf_flcount)
delta = need - pag->pagf_flcount;

@@ -1880,10 +1880,8 @@ xfs_alloc_fix_freelist(
int flags) /* XFS_ALLOC_FLAG_... */
{
xfs_buf_t *agbp; /* agf buffer pointer */
- xfs_agf_t *agf; /* a.g. freespace structure pointer */
xfs_buf_t *agflbp;/* agfl buffer pointer */
xfs_agblock_t bno; /* freelist block */
- xfs_extlen_t delta; /* new blocks needed in freelist */
int error; /* error result code */
xfs_extlen_t longest;/* longest extent in allocation group */
xfs_mount_t *mp; /* file system mount point structure */
@@ -1927,7 +1925,7 @@ xfs_alloc_fix_freelist(
* total blocks, reject it.
*/
need = XFS_MIN_FREELIST_PAG(pag, mp);
- longest = xfs_alloc_longest_free_extent(mp, pag);
+ longest = xfs_alloc_longest_free_extent(mp, pag, need);
if ((args->minlen + args->alignment + args->minalignslop - 1) >
longest ||
((int)(pag->pagf_freeblks + pag->pagf_flcount -
@@ -1954,25 +1952,16 @@ xfs_alloc_fix_freelist(
return 0;
}
}
- /*
- * Figure out how many blocks we should have in the freelist.
- */
- agf = XFS_BUF_TO_AGF(agbp);
- need = XFS_MIN_FREELIST(agf, mp);
- /*
- * If there isn't enough total or single-extent, reject it.
- */
+
+
+ /* If there isn't enough total space or single-extent, reject it. */
+ need = XFS_MIN_FREELIST_PAG(pag, mp);
if (!(flags & XFS_ALLOC_FLAG_FREEING)) {
- delta = need > be32_to_cpu(agf->agf_flcount) ?
- (need - be32_to_cpu(agf->agf_flcount)) : 0;
- longest = be32_to_cpu(agf->agf_longest);
- longest = (longest > delta) ? (longest - delta) :
- (be32_to_cpu(agf->agf_flcount) > 0 || longest > 0);
+ longest = xfs_alloc_longest_free_extent(mp, pag, need);
if ((args->minlen + args->alignment + args->minalignslop - 1) >
longest ||
- ((int)(be32_to_cpu(agf->agf_freeblks) +
- be32_to_cpu(agf->agf_flcount) - need - args->total) <
- (int)args->minleft)) {
+ ((int)(pag->pagf_freeblks + pag->pagf_flcount -
+ need - args->total) < (int)args->minleft)) {
xfs_trans_brelse(tp, agbp);
args->agbp = NULL;
return 0;
@@ -1980,21 +1969,25 @@ xfs_alloc_fix_freelist(
}
/*
* Make the freelist shorter if it's too long.
+ *
+ * XXX (dgc): When we have lots of free space, does this buy us
+ * anything other than extra overhead when we need to put more blocks
+ * back on the free list? Maybe we should only do this when space is
+ * getting low or the AGFL is more than half full?
*/
- while (be32_to_cpu(agf->agf_flcount) > need) {
- xfs_buf_t *bp;
+ while (pag->pagf_flcount > need) {
+ struct xfs_buf *bp;

error = xfs_alloc_get_freelist(tp, agbp, &bno, 0);
if (error)
return error;
- if ((error = xfs_free_ag_extent(tp, agbp, args->agno, bno, 1, 1)))
+ error = xfs_free_ag_extent(tp, agbp, args->agno, bno, 1, 1);
+ if (error)
return error;
bp = xfs_btree_get_bufs(mp, tp, args->agno, bno, 0);
xfs_trans_binval(tp, bp);
}
- /*
- * Initialize the args structure.
- */
+
memset(&targs, 0, sizeof(targs));
targs.tp = tp;
targs.mp = mp;
@@ -2003,18 +1996,18 @@ xfs_alloc_fix_freelist(
targs.alignment = targs.minlen = targs.prod = targs.isfl = 1;
targs.type = XFS_ALLOCTYPE_THIS_AG;
targs.pag = pag;
- if ((error = xfs_alloc_read_agfl(mp, tp, targs.agno, &agflbp)))
+ error = xfs_alloc_read_agfl(mp, tp, targs.agno, &agflbp);
+ if (error)
return error;
- /*
- * Make the freelist longer if it's too short.
- */
- while (be32_to_cpu(agf->agf_flcount) < need) {
+
+ /* Make the freelist longer if it's too short. */
+ while (pag->pagf_flcount < need) {
targs.agbno = 0;
- targs.maxlen = need - be32_to_cpu(agf->agf_flcount);
- /*
- * Allocate as many blocks as possible at once.
- */
- if ((error = xfs_alloc_ag_vextent(&targs))) {
+ targs.maxlen = need - pag->pagf_flcount;
+
+ /* Allocate as many blocks as possible at once. */
+ error = xfs_alloc_ag_vextent(&targs);
+ if (error) {
xfs_trans_brelse(tp, agflbp);
return error;
}
diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h
index 29f27b2..a4d3b9a 100644
--- a/fs/xfs/libxfs/xfs_alloc.h
+++ b/fs/xfs/libxfs/xfs_alloc.h
@@ -130,12 +130,8 @@ typedef struct xfs_alloc_arg {
#define XFS_ALLOC_USERDATA 1 /* allocation is for user data*/
#define XFS_ALLOC_INITIAL_USER_DATA 2 /* special case start of file */

-/*
- * Find the length of the longest extent in an AG.
- */
-xfs_extlen_t
-xfs_alloc_longest_free_extent(struct xfs_mount *mp,
- struct xfs_perag *pag);
+xfs_extlen_t xfs_alloc_longest_free_extent(struct xfs_mount *mp,
+ struct xfs_perag *pag, xfs_extlen_t need);

/*
* Compute and fill in value of m_ag_maxlevels.
diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 5cb3e85..7382cce 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -3521,7 +3521,8 @@ xfs_bmap_longest_free_extent(
}
}

- longest = xfs_alloc_longest_free_extent(mp, pag);
+ longest = xfs_alloc_longest_free_extent(mp, pag,
+ XFS_MIN_FREELIST_PAG(pag, mp));
if (*blen < longest)
*blen = longest;

diff --git a/fs/xfs/xfs_filestream.c b/fs/xfs/xfs_filestream.c
index da82f1c..9ac5eaa 100644
--- a/fs/xfs/xfs_filestream.c
+++ b/fs/xfs/xfs_filestream.c
@@ -196,7 +196,8 @@ xfs_filestream_pick_ag(
goto next_ag;
}

- longest = xfs_alloc_longest_free_extent(mp, pag);
+ longest = xfs_alloc_longest_free_extent(mp, pag,
+ XFS_MIN_FREELIST_PAG(pag, mp));
if (((minlen && longest >= minlen) ||
(!minlen && pag->pagf_freeblks >= minfree)) &&
(!pag->pagf_metadata || !(flags & XFS_PICK_USERDATA) ||