298f7bec50
When we dirty an inode, we are going to have to write it disk at some point in the near future. This requires the inode cluster backing buffer to be present in memory. Unfortunately, under severe memory pressure we can reclaim the inode backing buffer while the inode is dirty in memory, resulting in stalling the AIL pushing because it has to do a read-modify-write cycle on the cluster buffer. When we have no memory available, the read of the cluster buffer blocks the AIL pushing process, and this causes all sorts of issues for memory reclaim as it requires inode writeback to make forwards progress. Allocating a cluster buffer causes more memory pressure, and results in more cluster buffers to be reclaimed, resulting in more RMW cycles to be done in the AIL context and everything then backs up on AIL progress. Only the synchronous inode cluster writeback in the the inode reclaim code provides some level of forwards progress guarantees that prevent OOM-killer rampages in this situation. Fix this by pinning the inode backing buffer to the inode log item when the inode is first dirtied (i.e. in xfs_trans_log_inode()). This may mean the first modification of an inode that has been held in cache for a long time may block on a cluster buffer read, but we can do that in transaction context and block safely until the buffer has been allocated and read. Once we have the cluster buffer, the inode log item takes a reference to it, pinning it in memory, and attaches it to the log item for future reference. This means we can always grab the cluster buffer from the inode log item when we need it. When the inode is finally cleaned and removed from the AIL, we can drop the reference the inode log item holds on the cluster buffer. Once all inodes on the cluster buffer are clean, the cluster buffer will be unpinned and it will be available for memory reclaim to reclaim again. This avoids the issues with needing to do RMW cycles in the AIL pushing context, and hence allows complete non-blocking inode flushing to be performed by the AIL pushing context. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
198 lines
5.6 KiB
C
198 lines
5.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2000,2005 Silicon Graphics, Inc.
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* All Rights Reserved.
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*/
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#include "xfs.h"
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#include "xfs_fs.h"
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#include "xfs_shared.h"
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#include "xfs_format.h"
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#include "xfs_log_format.h"
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#include "xfs_trans_resv.h"
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#include "xfs_mount.h"
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#include "xfs_inode.h"
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#include "xfs_trans.h"
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#include "xfs_trans_priv.h"
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#include "xfs_inode_item.h"
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#include <linux/iversion.h>
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/*
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* Add a locked inode to the transaction.
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*
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* The inode must be locked, and it cannot be associated with any transaction.
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* If lock_flags is non-zero the inode will be unlocked on transaction commit.
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*/
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void
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xfs_trans_ijoin(
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struct xfs_trans *tp,
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struct xfs_inode *ip,
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uint lock_flags)
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{
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struct xfs_inode_log_item *iip;
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ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
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if (ip->i_itemp == NULL)
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xfs_inode_item_init(ip, ip->i_mount);
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iip = ip->i_itemp;
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ASSERT(iip->ili_lock_flags == 0);
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iip->ili_lock_flags = lock_flags;
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ASSERT(!xfs_iflags_test(ip, XFS_ISTALE));
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/*
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* Get a log_item_desc to point at the new item.
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*/
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xfs_trans_add_item(tp, &iip->ili_item);
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}
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/*
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* Transactional inode timestamp update. Requires the inode to be locked and
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* joined to the transaction supplied. Relies on the transaction subsystem to
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* track dirty state and update/writeback the inode accordingly.
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*/
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void
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xfs_trans_ichgtime(
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struct xfs_trans *tp,
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struct xfs_inode *ip,
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int flags)
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{
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struct inode *inode = VFS_I(ip);
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struct timespec64 tv;
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ASSERT(tp);
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ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
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tv = current_time(inode);
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if (flags & XFS_ICHGTIME_MOD)
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inode->i_mtime = tv;
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if (flags & XFS_ICHGTIME_CHG)
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inode->i_ctime = tv;
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if (flags & XFS_ICHGTIME_CREATE)
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ip->i_d.di_crtime = tv;
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}
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/*
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* This is called to mark the fields indicated in fieldmask as needing to be
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* logged when the transaction is committed. The inode must already be
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* associated with the given transaction.
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*
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* The values for fieldmask are defined in xfs_inode_item.h. We always log all
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* of the core inode if any of it has changed, and we always log all of the
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* inline data/extents/b-tree root if any of them has changed.
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*
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* Grab and pin the cluster buffer associated with this inode to avoid RMW
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* cycles at inode writeback time. Avoid the need to add error handling to every
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* xfs_trans_log_inode() call by shutting down on read error. This will cause
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* transactions to fail and everything to error out, just like if we return a
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* read error in a dirty transaction and cancel it.
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*/
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void
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xfs_trans_log_inode(
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struct xfs_trans *tp,
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struct xfs_inode *ip,
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uint flags)
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{
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struct xfs_inode_log_item *iip = ip->i_itemp;
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struct inode *inode = VFS_I(ip);
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uint iversion_flags = 0;
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ASSERT(iip);
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ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
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ASSERT(!xfs_iflags_test(ip, XFS_ISTALE));
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tp->t_flags |= XFS_TRANS_DIRTY;
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/*
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* Don't bother with i_lock for the I_DIRTY_TIME check here, as races
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* don't matter - we either will need an extra transaction in 24 hours
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* to log the timestamps, or will clear already cleared fields in the
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* worst case.
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*/
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if (inode->i_state & (I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED)) {
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spin_lock(&inode->i_lock);
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inode->i_state &= ~(I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED);
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spin_unlock(&inode->i_lock);
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}
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/*
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* First time we log the inode in a transaction, bump the inode change
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* counter if it is configured for this to occur. While we have the
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* inode locked exclusively for metadata modification, we can usually
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* avoid setting XFS_ILOG_CORE if no one has queried the value since
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* the last time it was incremented. If we have XFS_ILOG_CORE already
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* set however, then go ahead and bump the i_version counter
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* unconditionally.
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*/
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if (!test_and_set_bit(XFS_LI_DIRTY, &iip->ili_item.li_flags)) {
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if (IS_I_VERSION(inode) &&
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inode_maybe_inc_iversion(inode, flags & XFS_ILOG_CORE))
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iversion_flags = XFS_ILOG_CORE;
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}
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/*
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* Record the specific change for fdatasync optimisation. This allows
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* fdatasync to skip log forces for inodes that are only timestamp
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* dirty.
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*/
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spin_lock(&iip->ili_lock);
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iip->ili_fsync_fields |= flags;
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if (!iip->ili_item.li_buf) {
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struct xfs_buf *bp;
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int error;
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/*
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* We hold the ILOCK here, so this inode is not going to be
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* flushed while we are here. Further, because there is no
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* buffer attached to the item, we know that there is no IO in
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* progress, so nothing will clear the ili_fields while we read
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* in the buffer. Hence we can safely drop the spin lock and
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* read the buffer knowing that the state will not change from
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* here.
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*/
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spin_unlock(&iip->ili_lock);
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error = xfs_imap_to_bp(ip->i_mount, tp, &ip->i_imap, NULL,
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&bp, 0);
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if (error) {
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xfs_force_shutdown(ip->i_mount, SHUTDOWN_META_IO_ERROR);
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return;
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}
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/*
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* We need an explicit buffer reference for the log item but
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* don't want the buffer to remain attached to the transaction.
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* Hold the buffer but release the transaction reference.
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*/
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xfs_buf_hold(bp);
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xfs_trans_brelse(tp, bp);
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spin_lock(&iip->ili_lock);
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iip->ili_item.li_buf = bp;
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}
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/*
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* Always OR in the bits from the ili_last_fields field. This is to
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* coordinate with the xfs_iflush() and xfs_iflush_done() routines in
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* the eventual clearing of the ili_fields bits. See the big comment in
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* xfs_iflush() for an explanation of this coordination mechanism.
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*/
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iip->ili_fields |= (flags | iip->ili_last_fields | iversion_flags);
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spin_unlock(&iip->ili_lock);
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}
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int
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xfs_trans_roll_inode(
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struct xfs_trans **tpp,
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struct xfs_inode *ip)
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{
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int error;
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xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
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error = xfs_trans_roll(tpp);
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if (!error)
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xfs_trans_ijoin(*tpp, ip, 0);
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return error;
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}
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