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xfs: xfs_log_force_lsn isn't passed a LSN

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commit 5f9b4b0de8dc2fb8eb655463b438001c111570fe upstream.

[backported from CIL scalability series for dependency]

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 <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dave Chinner
2022-07-29 18:16:02 +02:00
committed by Greg Kroah-Hartman
parent 41fbfdaba9
commit 6d3605f84e
13 changed files with 56 additions and 65 deletions
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14
fs/xfs/xfs_file.c
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@@ -118,8 +118,8 @@ xfs_dir_fsync(
return xfs_log_force_inode(ip);
}
static xfs_lsn_t
xfs_fsync_lsn(
static xfs_csn_t
xfs_fsync_seq(
struct xfs_inode *ip,
bool datasync)
{
@@ -127,7 +127,7 @@ xfs_fsync_lsn(
return 0;
if (datasync && !(ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
return 0;
return ip->i_itemp->ili_last_lsn;
return ip->i_itemp->ili_commit_seq;
}
/*
@@ -150,12 +150,12 @@ xfs_fsync_flush_log(
int *log_flushed)
{
int error = 0;
xfs_lsn_t lsn;
xfs_csn_t seq;
xfs_ilock(ip, XFS_ILOCK_SHARED);
lsn = xfs_fsync_lsn(ip, datasync);
if (lsn) {
error = xfs_log_force_lsn(ip->i_mount, lsn, XFS_LOG_SYNC,
seq = xfs_fsync_seq(ip, datasync);
if (seq) {
error = xfs_log_force_seq(ip->i_mount, seq, XFS_LOG_SYNC,
log_flushed);
spin_lock(&ip->i_itemp->ili_lock);