linux/fs/xfs/xfs_inode_item.h
Dave Chinner 5f9b4b0de8 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 <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>
2021-06-21 10:12:33 -07:00

53 lines
1.8 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2000,2005 Silicon Graphics, Inc.
* All Rights Reserved.
*/
#ifndef __XFS_INODE_ITEM_H__
#define __XFS_INODE_ITEM_H__
/* kernel only definitions */
struct xfs_buf;
struct xfs_bmbt_rec;
struct xfs_inode;
struct xfs_mount;
struct xfs_inode_log_item {
struct xfs_log_item ili_item; /* common portion */
struct xfs_inode *ili_inode; /* inode ptr */
unsigned short ili_lock_flags; /* inode lock flags */
/*
* The ili_lock protects the interactions between the dirty state and
* the flush state of the inode log item. This allows us to do atomic
* modifications of multiple state fields without having to hold a
* specific inode lock to serialise them.
*
* We need atomic changes between inode dirtying, inode flushing and
* inode completion, but these all hold different combinations of
* ILOCK and IFLUSHING and hence we need some other method of
* serialising updates to the flush state.
*/
spinlock_t ili_lock; /* flush state lock */
unsigned int ili_last_fields; /* fields when flushed */
unsigned int ili_fields; /* fields to be logged */
unsigned int ili_fsync_fields; /* logged since last fsync */
xfs_lsn_t ili_flush_lsn; /* lsn at last flush */
xfs_csn_t ili_commit_seq; /* last transaction commit */
};
static inline int xfs_inode_clean(struct xfs_inode *ip)
{
return !ip->i_itemp || !(ip->i_itemp->ili_fields & XFS_ILOG_ALL);
}
extern void xfs_inode_item_init(struct xfs_inode *, struct xfs_mount *);
extern void xfs_inode_item_destroy(struct xfs_inode *);
extern void xfs_iflush_abort(struct xfs_inode *);
extern int xfs_inode_item_format_convert(xfs_log_iovec_t *,
struct xfs_inode_log_format *);
extern struct kmem_zone *xfs_ili_zone;
#endif /* __XFS_INODE_ITEM_H__ */