Refactor the AG selection loop in xfs_dialloc to operate on the in-memory
perag data as much as possible. We only read the AGI buffer once we have
selected an AG to allocate inodes now instead of for every AG considered.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/xfs/xfs_ialloc.c | 127 ++++++++++++++++++++++++++++------------------------
1 file changed, 69 insertions(+), 58 deletions(-)
Index: xfs/fs/xfs/xfs_ialloc.c
===================================================================
--- xfs.orig/fs/xfs/xfs_ialloc.c 2012-06-04 12:54:53.000000000 -0400
+++ xfs/fs/xfs/xfs_ialloc.c 2012-06-04 12:58:07.104263361 -0400
@@ -900,11 +900,10 @@ xfs_dialloc(
xfs_mount_t *mp = tp->t_mountp;
xfs_buf_t *agbp; /* allocation group header's buffer */
xfs_agnumber_t agno; /* allocation group number */
- xfs_agi_t *agi; /* allocation group header structure */
int error; /* error return value */
int ialloced; /* inode allocation status */
int noroom = 0; /* no space for inode blk allocation */
- xfs_agnumber_t tagno; /* testing allocation group number */
+ xfs_agnumber_t start_agno; /* starting allocation group number */
struct xfs_perag *pag;
if (*IO_agbp) {
@@ -921,25 +920,17 @@ xfs_dialloc(
* We do not have an agbp, so select an initial allocation
* group for inode allocation.
*/
- agno = xfs_ialloc_ag_select(tp, parent, mode, okalloc);
- if (agno == NULLAGNUMBER) {
+ start_agno = xfs_ialloc_ag_select(tp, parent, mode, okalloc);
+ if (start_agno == NULLAGNUMBER) {
*inop = NULLFSINO;
return 0;
}
- error = xfs_ialloc_read_agi(mp, tp, agno, &agbp);
- if (error)
- return XFS_ERROR(error);
- agi = XFS_BUF_TO_AGI(agbp);
-
- tagno = agno;
-
/*
* If we have already hit the ceiling of inode blocks then clear
* okalloc so we scan all available agi structures for a free
* inode.
*/
-
if (mp->m_maxicount &&
mp->m_sb.sb_icount + XFS_IALLOC_INODES(mp) > mp->m_maxicount) {
noroom = 1;
@@ -951,67 +942,87 @@ xfs_dialloc(
* or in which we can allocate some inodes. Iterate through the
* allocation groups upward, wrapping at the end.
*/
- while (!agi->agi_freecount) {
- /*
- * Don't do anything if we're not supposed to allocate
- * any blocks, just go on to the next ag.
- */
- if (okalloc) {
- /*
- * Try to allocate some new inodes in the allocation
- * group.
- */
- if ((error = xfs_ialloc_ag_alloc(tp, agbp, &ialloced))) {
- xfs_trans_brelse(tp, agbp);
- if (error == ENOSPC) {
- *inop = NULLFSINO;
- return 0;
- } else
- return error;
- }
- if (ialloced) {
- /*
- * We successfully allocated some inodes, return
- * the current context to the caller so that it
- * can commit the current transaction and call
- * us again where we left off.
- */
- ASSERT(be32_to_cpu(agi->agi_freecount) > 0);
- *IO_agbp = agbp;
- *inop = NULLFSINO;
- return 0;
- }
+ agno = start_agno;
+ for (;;) {
+ pag = xfs_perag_get(mp, agno);
+ if (!pag->pagi_inodeok) {
+ xfs_ialloc_next_ag(mp);
+ goto nextag;
+ }
+
+ if (!pag->pagi_init) {
+ error = xfs_ialloc_pagi_init(mp, tp, agno);
+ if (error)
+ goto out_error;
}
+
/*
- * If it failed, give up on this ag.
+ * Do a first racy fast path check if this AG is usable.
*/
- xfs_trans_brelse(tp, agbp);
+ if (!pag->pagi_freecount && !okalloc)
+ goto nextag;
+
+ error = xfs_ialloc_read_agi(mp, tp, agno, &agbp);
+ if (error)
+ goto out_error;
+
/*
- * Go on to the next ag: get its ag header.
+ * Once the AGI has been read in we have to recheck
+ * pagi_freecount with the AGI buffer lock held.
*/
-nextag:
- if (++tagno == mp->m_sb.sb_agcount)
- tagno = 0;
- if (tagno == agno) {
+ if (pag->pagi_freecount) {
+ xfs_perag_put(pag);
+ goto out_alloc;
+ }
+
+ if (!okalloc) {
+ xfs_trans_brelse(tp, agbp);
+ goto nextag;
+ }
+
+ error = xfs_ialloc_ag_alloc(tp, agbp, &ialloced);
+ if (error) {
+ xfs_trans_brelse(tp, agbp);
+
+ if (error != ENOSPC)
+ goto out_error;
+
+ xfs_perag_put(pag);
*inop = NULLFSINO;
- return noroom ? ENOSPC : 0;
+ return 0;
}
- pag = xfs_perag_get(mp, tagno);
- if (pag->pagi_inodeok == 0) {
+
+ if (ialloced) {
+ /*
+ * We successfully allocated some inodes, return
+ * the current context to the caller so that it
+ * can commit the current transaction and call
+ * us again where we left off.
+ */
+ ASSERT(pag->pagi_freecount > 0);
xfs_perag_put(pag);
- goto nextag;
+
+ *IO_agbp = agbp;
+ *inop = NULLFSINO;
+ return 0;
}
- error = xfs_ialloc_read_agi(mp, tp, tagno, &agbp);
+
+nextag:
xfs_perag_put(pag);
- if (error)
- goto nextag;
- agi = XFS_BUF_TO_AGI(agbp);
- ASSERT(agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC));
+ if (++agno == mp->m_sb.sb_agcount)
+ agno = 0;
+ if (agno == start_agno) {
+ *inop = NULLFSINO;
+ return noroom ? ENOSPC : 0;
+ }
}
out_alloc:
*IO_agbp = NULL;
return xfs_dialloc_ag(tp, agbp, parent, inop);
+out_error:
+ xfs_perag_put(pag);
+ return XFS_ERROR(error);
}
/*
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