From 5f9b4b0de8dc2fb8eb655463b438001c111570fe Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Fri, 18 Jun 2021 08:21:52 -0700 Subject: xfs: xfs_log_force_lsn isn't passed a LSN In doing an investigation into AIL push stalls, I was looking at the log force code to see if an async CIL push could be done instead. This lead me to xfs_log_force_lsn() and looking at how it works. xfs_log_force_lsn() is only called from inode synchronisation contexts such as fsync(), and it takes the ip->i_itemp->ili_last_lsn value as the LSN to sync the log to. This gets passed to xlog_cil_force_lsn() via xfs_log_force_lsn() to flush the CIL to the journal, and then used by xfs_log_force_lsn() to flush the iclogs to the journal. The problem is that ip->i_itemp->ili_last_lsn does not store a log sequence number. What it stores is passed to it from the ->iop_committing method, which is called by xfs_log_commit_cil(). The value this passes to the iop_committing method is the CIL context sequence number that the item was committed to. As it turns out, xlog_cil_force_lsn() converts the sequence to an actual commit LSN for the related context and returns that to xfs_log_force_lsn(). xfs_log_force_lsn() overwrites it's "lsn" variable that contained a sequence with an actual LSN and then uses that to sync the iclogs. This caused me some confusion for a while, even though I originally wrote all this code a decade ago. ->iop_committing is only used by a couple of log item types, and only inode items use the sequence number it is passed. Let's clean up the API, CIL structures and inode log item to call it a sequence number, and make it clear that the high level code is using CIL sequence numbers and not on-disk LSNs for integrity synchronisation purposes. Signed-off-by: Dave Chinner Reviewed-by: Brian Foster Reviewed-by: Darrick J. Wong Reviewed-by: Allison Henderson Signed-off-by: Darrick J. Wong --- fs/xfs/xfs_log_cil.c | 30 +++++++++++------------------- 1 file changed, 11 insertions(+), 19 deletions(-) (limited to 'fs/xfs/xfs_log_cil.c') diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c index 903617e6d054..3c2b1205944d 100644 --- a/fs/xfs/xfs_log_cil.c +++ b/fs/xfs/xfs_log_cil.c @@ -788,7 +788,7 @@ xlog_cil_push_work( * that higher sequences will wait for us to write out a commit record * before they do. * - * xfs_log_force_lsn requires us to mirror the new sequence into the cil + * xfs_log_force_seq requires us to mirror the new sequence into the cil * structure atomically with the addition of this sequence to the * committing list. This also ensures that we can do unlocked checks * against the current sequence in log forces without risking @@ -1057,16 +1057,14 @@ xlog_cil_empty( * allowed again. */ void -xfs_log_commit_cil( - struct xfs_mount *mp, +xlog_cil_commit( + struct xlog *log, struct xfs_trans *tp, - xfs_lsn_t *commit_lsn, + xfs_csn_t *commit_seq, bool regrant) { - struct xlog *log = mp->m_log; struct xfs_cil *cil = log->l_cilp; struct xfs_log_item *lip, *next; - xfs_lsn_t xc_commit_lsn; /* * Do all necessary memory allocation before we lock the CIL. @@ -1080,10 +1078,6 @@ xfs_log_commit_cil( xlog_cil_insert_items(log, tp); - xc_commit_lsn = cil->xc_ctx->sequence; - if (commit_lsn) - *commit_lsn = xc_commit_lsn; - if (regrant && !XLOG_FORCED_SHUTDOWN(log)) xfs_log_ticket_regrant(log, tp->t_ticket); else @@ -1106,8 +1100,10 @@ xfs_log_commit_cil( list_for_each_entry_safe(lip, next, &tp->t_items, li_trans) { xfs_trans_del_item(lip); if (lip->li_ops->iop_committing) - lip->li_ops->iop_committing(lip, xc_commit_lsn); + lip->li_ops->iop_committing(lip, cil->xc_ctx->sequence); } + if (commit_seq) + *commit_seq = cil->xc_ctx->sequence; /* xlog_cil_push_background() releases cil->xc_ctx_lock */ xlog_cil_push_background(log); @@ -1124,9 +1120,9 @@ xfs_log_commit_cil( * iclog flush is necessary following this call. */ xfs_lsn_t -xlog_cil_force_lsn( +xlog_cil_force_seq( struct xlog *log, - xfs_lsn_t sequence) + xfs_csn_t sequence) { struct xfs_cil *cil = log->l_cilp; struct xfs_cil_ctx *ctx; @@ -1222,21 +1218,17 @@ bool xfs_log_item_in_current_chkpt( struct xfs_log_item *lip) { - struct xfs_cil_ctx *ctx; + struct xfs_cil_ctx *ctx = lip->li_mountp->m_log->l_cilp->xc_ctx; if (list_empty(&lip->li_cil)) return false; - ctx = lip->li_mountp->m_log->l_cilp->xc_ctx; - /* * li_seq is written on the first commit of a log item to record the * first checkpoint it is written to. Hence if it is different to the * current sequence, we're in a new checkpoint. */ - if (XFS_LSN_CMP(lip->li_seq, ctx->sequence) != 0) - return false; - return true; + return lip->li_seq == ctx->sequence; } /* -- cgit v1.2.3