From 507630b29f13a3d8689895618b12015308402e22 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Tue, 27 Mar 2012 10:34:50 -0400 Subject: [PATCH] xfs: use shared ilock mode for direct IO writes by default For the direct IO write path, we only really need the ilock to be taken in exclusive mode during IO submission if we need to do extent allocation instead of all the time. Change the block mapping code to take the ilock in shared mode for the initial block mapping, and only retake it exclusively when we actually have to perform extent allocations. We were already dropping the ilock for the transaction allocation, so this doesn't introduce new race windows. Based on an earlier patch from Dave Chinner. Signed-off-by: Christoph Hellwig Reviewed-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers --- fs/xfs/xfs_aops.c | 30 ++++++++++++++++++++++++++---- fs/xfs/xfs_iomap.c | 45 +++++++++++++++++++-------------------------- 2 files changed, 45 insertions(+), 30 deletions(-) diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c index 0dbb9e70fe21..0fd7c2bfa402 100644 --- a/fs/xfs/xfs_aops.c +++ b/fs/xfs/xfs_aops.c @@ -1146,7 +1146,14 @@ __xfs_get_blocks( if (!create && direct && offset >= i_size_read(inode)) return 0; - if (create) { + /* + * Direct I/O is usually done on preallocated files, so try getting + * a block mapping without an exclusive lock first. For buffered + * writes we already have the exclusive iolock anyway, so avoiding + * a lock roundtrip here by taking the ilock exclusive from the + * beginning is a useful micro optimization. + */ + if (create && !direct) { lockmode = XFS_ILOCK_EXCL; xfs_ilock(ip, lockmode); } else { @@ -1169,22 +1176,37 @@ __xfs_get_blocks( (imap.br_startblock == HOLESTARTBLOCK || imap.br_startblock == DELAYSTARTBLOCK))) { if (direct) { + /* + * Drop the ilock in preparation for starting the block + * allocation transaction. It will be retaken + * exclusively inside xfs_iomap_write_direct for the + * actual allocation. + */ + xfs_iunlock(ip, lockmode); error = xfs_iomap_write_direct(ip, offset, size, &imap, nimaps); + if (error) + return -error; } else { + /* + * Delalloc reservations do not require a transaction, + * we can go on without dropping the lock here. + */ error = xfs_iomap_write_delay(ip, offset, size, &imap); + if (error) + goto out_unlock; + + xfs_iunlock(ip, lockmode); } - if (error) - goto out_unlock; trace_xfs_get_blocks_alloc(ip, offset, size, 0, &imap); } else if (nimaps) { trace_xfs_get_blocks_found(ip, offset, size, 0, &imap); + xfs_iunlock(ip, lockmode); } else { trace_xfs_get_blocks_notfound(ip, offset, size); goto out_unlock; } - xfs_iunlock(ip, lockmode); if (imap.br_startblock != HOLESTARTBLOCK && imap.br_startblock != DELAYSTARTBLOCK) { diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index 71a464503c43..47e714a7bf92 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -142,11 +142,7 @@ xfs_iomap_write_direct( int committed; int error; - /* - * Make sure that the dquots are there. This doesn't hold - * the ilock across a disk read. - */ - error = xfs_qm_dqattach_locked(ip, 0); + error = xfs_qm_dqattach(ip, 0); if (error) return XFS_ERROR(error); @@ -158,7 +154,7 @@ xfs_iomap_write_direct( if ((offset + count) > XFS_ISIZE(ip)) { error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb); if (error) - goto error_out; + return XFS_ERROR(error); } else { if (nmaps && (imap->br_startblock == HOLESTARTBLOCK)) last_fsb = MIN(last_fsb, (xfs_fileoff_t) @@ -190,7 +186,6 @@ xfs_iomap_write_direct( /* * Allocate and setup the transaction */ - xfs_iunlock(ip, XFS_ILOCK_EXCL); tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT); error = xfs_trans_reserve(tp, resblks, XFS_WRITE_LOG_RES(mp), resrtextents, @@ -199,15 +194,16 @@ xfs_iomap_write_direct( /* * Check for running out of space, note: need lock to return */ - if (error) + if (error) { xfs_trans_cancel(tp, 0); + return XFS_ERROR(error); + } + xfs_ilock(ip, XFS_ILOCK_EXCL); - if (error) - goto error_out; error = xfs_trans_reserve_quota_nblks(tp, ip, qblocks, 0, quota_flag); if (error) - goto error1; + goto out_trans_cancel; xfs_trans_ijoin(tp, ip, 0); @@ -224,42 +220,39 @@ xfs_iomap_write_direct( error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb, bmapi_flag, &firstfsb, 0, imap, &nimaps, &free_list); if (error) - goto error0; + goto out_bmap_cancel; /* * Complete the transaction */ error = xfs_bmap_finish(&tp, &free_list, &committed); if (error) - goto error0; + goto out_bmap_cancel; error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES); if (error) - goto error_out; + goto out_unlock; /* * Copy any maps to caller's array and return any error. */ if (nimaps == 0) { - error = ENOSPC; - goto error_out; + error = XFS_ERROR(ENOSPC); + goto out_unlock; } - if (!(imap->br_startblock || XFS_IS_REALTIME_INODE(ip))) { + if (!(imap->br_startblock || XFS_IS_REALTIME_INODE(ip))) error = xfs_alert_fsblock_zero(ip, imap); - goto error_out; - } - return 0; +out_unlock: + xfs_iunlock(ip, XFS_ILOCK_EXCL); + return error; -error0: /* Cancel bmap, unlock inode, unreserve quota blocks, cancel trans */ +out_bmap_cancel: xfs_bmap_cancel(&free_list); xfs_trans_unreserve_quota_nblks(tp, ip, qblocks, 0, quota_flag); - -error1: /* Just cancel transaction */ +out_trans_cancel: xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT); - -error_out: - return XFS_ERROR(error); + goto out_unlock; } /* -- 2.30.2