From be60fe54b216a62403b816d3930a66ad7c51cbc6 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 4 Jul 2012 10:54:50 -0400 Subject: [PATCH] xfs: do not read the AGI buffer in xfs_dialloc until nessecary 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 Reviewed-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers --- fs/xfs/xfs_ialloc.c | 127 ++++++++++++++++++++++++-------------------- 1 file changed, 69 insertions(+), 58 deletions(-) diff --git a/fs/xfs/xfs_ialloc.c b/fs/xfs/xfs_ialloc.c index ecb9f22a7f35..21e37b55f7e5 100644 --- a/fs/xfs/xfs_ialloc.c +++ b/fs/xfs/xfs_ialloc.c @@ -900,11 +900,10 @@ xfs_dialloc( struct xfs_mount *mp = tp->t_mountp; struct xfs_buf *agbp; xfs_agnumber_t agno; - struct xfs_agi *agi; int error; int ialloced; int noroom = 0; - xfs_agnumber_t tagno; + xfs_agnumber_t start_agno; 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); } /* -- 2.34.1