From: "Darrick J. Wong" <djwong@kernel.org>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
Dave Chinner <david@fromorbit.com>,
ceph-devel@vger.kernel.org, Chao Yu <yuchao0@huawei.com>,
Damien Le Moal <damien.lemoal@wdc.com>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Jaegeuk Kim <jaegeuk@kernel.org>,
Jeff Layton <jlayton@kernel.org>,
Johannes Thumshirn <jth@kernel.org>,
linux-cifs@vger.kernel.org, linux-ext4@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net, linux-mm@kvack.org,
linux-xfs@vger.kernel.org, Miklos Szeredi <miklos@szeredi.hu>,
Steve French <sfrench@samba.org>, Ted Tso <tytso@mit.edu>,
Matthew Wilcox <willy@infradead.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 07/13] xfs: Convert to use invalidate_lock
Date: Tue, 25 May 2021 14:37:29 -0700 [thread overview]
Message-ID: <20210525213729.GC202144@locust> (raw)
In-Reply-To: <20210525135100.11221-7-jack@suse.cz>
On Tue, May 25, 2021 at 03:50:44PM +0200, Jan Kara wrote:
> Use invalidate_lock instead of XFS internal i_mmap_lock. The intended
> purpose of invalidate_lock is exactly the same. Note that the locking in
> __xfs_filemap_fault() slightly changes as filemap_fault() already takes
> invalidate_lock.
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> CC: <linux-xfs@vger.kernel.org>
> CC: "Darrick J. Wong" <darrick.wong@oracle.com>
It's djwong@kernel.org now.
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
> fs/xfs/xfs_file.c | 12 ++++++-----
> fs/xfs/xfs_inode.c | 52 ++++++++++++++++++++++++++--------------------
> fs/xfs/xfs_inode.h | 1 -
> fs/xfs/xfs_super.c | 2 --
> 4 files changed, 36 insertions(+), 31 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 396ef36dcd0a..dc9cb5c20549 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1282,7 +1282,7 @@ xfs_file_llseek(
> *
> * mmap_lock (MM)
> * sb_start_pagefault(vfs, freeze)
> - * i_mmaplock (XFS - truncate serialisation)
> + * invalidate_lock (vfs/XFS_MMAPLOCK - truncate serialisation)
> * page_lock (MM)
> * i_lock (XFS - extent map serialisation)
> */
> @@ -1303,24 +1303,26 @@ __xfs_filemap_fault(
> file_update_time(vmf->vma->vm_file);
> }
>
> - xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
> if (IS_DAX(inode)) {
> pfn_t pfn;
>
> + xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
> ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL,
> (write_fault && !vmf->cow_page) ?
> &xfs_direct_write_iomap_ops :
> &xfs_read_iomap_ops);
> if (ret & VM_FAULT_NEEDDSYNC)
> ret = dax_finish_sync_fault(vmf, pe_size, pfn);
> + xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
> } else {
> - if (write_fault)
> + if (write_fault) {
> + xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
> ret = iomap_page_mkwrite(vmf,
> &xfs_buffered_write_iomap_ops);
> - else
> + xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
> + } else
> ret = filemap_fault(vmf);
> }
> - xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
>
> if (write_fault)
> sb_end_pagefault(inode->i_sb);
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 0369eb22c1bb..53bb5fc33621 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -131,7 +131,7 @@ xfs_ilock_attr_map_shared(
>
> /*
> * In addition to i_rwsem in the VFS inode, the xfs inode contains 2
> - * multi-reader locks: i_mmap_lock and the i_lock. This routine allows
> + * multi-reader locks: invalidate_lock and the i_lock. This routine allows
> * various combinations of the locks to be obtained.
> *
> * The 3 locks should always be ordered so that the IO lock is obtained first,
> @@ -139,23 +139,23 @@ xfs_ilock_attr_map_shared(
> *
> * Basic locking order:
> *
> - * i_rwsem -> i_mmap_lock -> page_lock -> i_ilock
> + * i_rwsem -> invalidate_lock -> page_lock -> i_ilock
> *
> * mmap_lock locking order:
> *
> * i_rwsem -> page lock -> mmap_lock
> - * mmap_lock -> i_mmap_lock -> page_lock
> + * mmap_lock -> invalidate_lock -> page_lock
> *
> * The difference in mmap_lock locking order mean that we cannot hold the
> - * i_mmap_lock over syscall based read(2)/write(2) based IO. These IO paths can
> - * fault in pages during copy in/out (for buffered IO) or require the mmap_lock
> - * in get_user_pages() to map the user pages into the kernel address space for
> - * direct IO. Similarly the i_rwsem cannot be taken inside a page fault because
> - * page faults already hold the mmap_lock.
> + * invalidate_lock over syscall based read(2)/write(2) based IO. These IO paths
> + * can fault in pages during copy in/out (for buffered IO) or require the
> + * mmap_lock in get_user_pages() to map the user pages into the kernel address
> + * space for direct IO. Similarly the i_rwsem cannot be taken inside a page
> + * fault because page faults already hold the mmap_lock.
> *
> * Hence to serialise fully against both syscall and mmap based IO, we need to
> - * take both the i_rwsem and the i_mmap_lock. These locks should *only* be both
> - * taken in places where we need to invalidate the page cache in a race
> + * take both the i_rwsem and the invalidate_lock. These locks should *only* be
> + * both taken in places where we need to invalidate the page cache in a race
> * free manner (e.g. truncate, hole punch and other extent manipulation
> * functions).
> */
> @@ -187,10 +187,13 @@ xfs_ilock(
> XFS_IOLOCK_DEP(lock_flags));
> }
>
> - if (lock_flags & XFS_MMAPLOCK_EXCL)
> - mrupdate_nested(&ip->i_mmaplock, XFS_MMAPLOCK_DEP(lock_flags));
> - else if (lock_flags & XFS_MMAPLOCK_SHARED)
> - mraccess_nested(&ip->i_mmaplock, XFS_MMAPLOCK_DEP(lock_flags));
> + if (lock_flags & XFS_MMAPLOCK_EXCL) {
> + down_write_nested(&VFS_I(ip)->i_mapping->invalidate_lock,
> + XFS_MMAPLOCK_DEP(lock_flags));
> + } else if (lock_flags & XFS_MMAPLOCK_SHARED) {
> + down_read_nested(&VFS_I(ip)->i_mapping->invalidate_lock,
> + XFS_MMAPLOCK_DEP(lock_flags));
> + }
>
> if (lock_flags & XFS_ILOCK_EXCL)
> mrupdate_nested(&ip->i_lock, XFS_ILOCK_DEP(lock_flags));
> @@ -239,10 +242,10 @@ xfs_ilock_nowait(
> }
>
> if (lock_flags & XFS_MMAPLOCK_EXCL) {
> - if (!mrtryupdate(&ip->i_mmaplock))
> + if (!down_write_trylock(&VFS_I(ip)->i_mapping->invalidate_lock))
> goto out_undo_iolock;
> } else if (lock_flags & XFS_MMAPLOCK_SHARED) {
> - if (!mrtryaccess(&ip->i_mmaplock))
> + if (!down_read_trylock(&VFS_I(ip)->i_mapping->invalidate_lock))
> goto out_undo_iolock;
> }
>
> @@ -257,9 +260,9 @@ xfs_ilock_nowait(
>
> out_undo_mmaplock:
> if (lock_flags & XFS_MMAPLOCK_EXCL)
> - mrunlock_excl(&ip->i_mmaplock);
> + up_write(&VFS_I(ip)->i_mapping->invalidate_lock);
> else if (lock_flags & XFS_MMAPLOCK_SHARED)
> - mrunlock_shared(&ip->i_mmaplock);
> + up_read(&VFS_I(ip)->i_mapping->invalidate_lock);
> out_undo_iolock:
> if (lock_flags & XFS_IOLOCK_EXCL)
> up_write(&VFS_I(ip)->i_rwsem);
> @@ -306,9 +309,9 @@ xfs_iunlock(
> up_read(&VFS_I(ip)->i_rwsem);
>
> if (lock_flags & XFS_MMAPLOCK_EXCL)
> - mrunlock_excl(&ip->i_mmaplock);
> + up_write(&VFS_I(ip)->i_mapping->invalidate_lock);
> else if (lock_flags & XFS_MMAPLOCK_SHARED)
> - mrunlock_shared(&ip->i_mmaplock);
> + up_read(&VFS_I(ip)->i_mapping->invalidate_lock);
>
> if (lock_flags & XFS_ILOCK_EXCL)
> mrunlock_excl(&ip->i_lock);
> @@ -334,7 +337,7 @@ xfs_ilock_demote(
> if (lock_flags & XFS_ILOCK_EXCL)
> mrdemote(&ip->i_lock);
> if (lock_flags & XFS_MMAPLOCK_EXCL)
> - mrdemote(&ip->i_mmaplock);
> + downgrade_write(&VFS_I(ip)->i_mapping->invalidate_lock);
> if (lock_flags & XFS_IOLOCK_EXCL)
> downgrade_write(&VFS_I(ip)->i_rwsem);
>
> @@ -355,8 +358,11 @@ xfs_isilocked(
>
> if (lock_flags & (XFS_MMAPLOCK_EXCL|XFS_MMAPLOCK_SHARED)) {
> if (!(lock_flags & XFS_MMAPLOCK_SHARED))
> - return !!ip->i_mmaplock.mr_writer;
> - return rwsem_is_locked(&ip->i_mmaplock.mr_lock);
> + return !debug_locks ||
> + lockdep_is_held_type(
> + &VFS_I(ip)->i_mapping->invalidate_lock,
> + 0);
> + return rwsem_is_locked(&VFS_I(ip)->i_mapping->invalidate_lock);
This doesn't look right...
If lockdep is disabled, we always return true for
xfs_isilocked(ip, XFS_MMAPLOCK_EXCL) even if nobody holds the lock?
Granted, you probably just copy-pasted from the IOLOCK_SHARED clause
beneath it. Er... oh right, preichl was messing with all that...
https://lore.kernel.org/linux-xfs/20201016021005.548850-2-preichl@redhat.com/
I guess I'll go have a look at that again.
--D
> }
>
> if (lock_flags & (XFS_IOLOCK_EXCL|XFS_IOLOCK_SHARED)) {
> diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
> index ca826cfba91c..a0e4153efbbe 100644
> --- a/fs/xfs/xfs_inode.h
> +++ b/fs/xfs/xfs_inode.h
> @@ -40,7 +40,6 @@ typedef struct xfs_inode {
> /* Transaction and locking information. */
> struct xfs_inode_log_item *i_itemp; /* logging information */
> mrlock_t i_lock; /* inode lock */
> - mrlock_t i_mmaplock; /* inode mmap IO lock */
> atomic_t i_pincount; /* inode pin count */
>
> /*
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index a2dab05332ac..eeaf44910b5f 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -715,8 +715,6 @@ xfs_fs_inode_init_once(
> atomic_set(&ip->i_pincount, 0);
> spin_lock_init(&ip->i_flags_lock);
>
> - mrlock_init(&ip->i_mmaplock, MRLOCK_ALLOW_EQUAL_PRI|MRLOCK_BARRIER,
> - "xfsino", ip->i_ino);
> mrlock_init(&ip->i_lock, MRLOCK_ALLOW_EQUAL_PRI|MRLOCK_BARRIER,
> "xfsino", ip->i_ino);
> }
> --
> 2.26.2
>
next prev parent reply other threads:[~2021-05-25 21:37 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-25 13:50 [PATCH 0/13 v6] fs: Hole punch vs page cache filling races Jan Kara
2021-05-25 13:50 ` [PATCH 01/13] mm: Fix comments mentioning i_mutex Jan Kara
2021-05-25 13:50 ` [PATCH 02/13] documentation: Sync file_operations members with reality Jan Kara
2021-05-25 20:43 ` Darrick J. Wong
2021-05-25 13:50 ` [PATCH 03/13] mm: Protect operations adding pages to page cache with invalidate_lock Jan Kara
2021-05-25 21:01 ` Darrick J. Wong
2021-05-26 10:00 ` Jan Kara
2021-05-25 13:50 ` [PATCH 04/13] mm: Add functions to lock invalidate_lock for two mappings Jan Kara
2021-05-25 20:48 ` Darrick J. Wong
2021-05-26 10:07 ` Jan Kara
2021-05-26 12:11 ` Damien Le Moal
2021-05-26 13:45 ` Jan Kara
2021-05-26 15:25 ` Darrick J. Wong
2021-05-25 13:50 ` [PATCH 05/13] ext4: Convert to use mapping->invalidate_lock Jan Kara
2021-05-25 13:50 ` [PATCH 06/13] ext2: Convert to using invalidate_lock Jan Kara
2021-05-25 13:50 ` [PATCH 07/13] xfs: Convert to use invalidate_lock Jan Kara
2021-05-25 21:37 ` Darrick J. Wong [this message]
2021-05-26 10:18 ` Jan Kara
2021-05-26 15:32 ` Darrick J. Wong
2021-05-27 12:01 ` Jan Kara
2021-05-25 21:40 ` Dave Chinner
2021-05-26 10:20 ` Jan Kara
2021-05-26 13:42 ` Jan Kara
2021-05-25 13:50 ` [PATCH 08/13] xfs: Convert double locking of MMAPLOCK to use VFS helpers Jan Kara
2021-05-25 21:41 ` Darrick J. Wong
2021-05-25 13:50 ` [PATCH 09/13] zonefs: Convert to using invalidate_lock Jan Kara
2021-05-25 13:50 ` [PATCH 10/13] f2fs: " Jan Kara
2021-05-26 9:55 ` Chao Yu
2021-05-25 13:50 ` [PATCH 11/13] fuse: " Jan Kara
2021-05-25 13:50 ` [PATCH 12/13] ceph: Fix race between hole punch and page fault Jan Kara
2021-05-25 13:50 ` [PATCH 13/13] cifs: " Jan Kara
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