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xfs: remove i_iolock and use i_rwsem in the VFS inode instead

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This patch drops the XFS-own i_iolock and uses the VFS i_rwsem which
recently replaced i_mutex instead.  This means we only have to take
one lock instead of two in many fast path operations, and we can
also shrink the xfs_inode structure.  Thanks to the xfs_ilock family
there is very little churn, the only thing of note is that we need
to switch to use the lock_two_directory helper for taking the i_rwsem
on two inodes in a few places to make sure our lock order matches
the one used in the VFS.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Christoph Hellwig 2016-11-30 14:33:25 +11:00 • committed by Dave Chinner
parent f8319483f5
commit 6552321831
14 changed files with 86 additions and 159 deletions
Download patch file Download diff file Expand all files Collapse all files

82
fs/xfs/xfs_inode.c
View file

@ -142,31 +142,31 @@ xfs_ilock_attr_map_shared(
}
/*
* The xfs inode contains 3 multi-reader locks: the i_iolock the i_mmap_lock and
* the i_lock. This routine allows various combinations of the locks to be
* obtained.
* 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
* various combinations of the locks to be obtained.
*
* The 3 locks should always be ordered so that the IO lock is obtained first,
* the mmap lock second and the ilock last in order to prevent deadlock.
*
* Basic locking order:
*
* i_iolock -> i_mmap_lock -> page_lock -> i_ilock
* i_rwsem -> i_mmap_lock -> page_lock -> i_ilock
*
* mmap_sem locking order:
*
* i_iolock -> page lock -> mmap_sem
* i_rwsem -> page lock -> mmap_sem
* mmap_sem -> i_mmap_lock -> page_lock
*
* The difference in mmap_sem 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_sem
* in get_user_pages() to map the user pages into the kernel address space for
* direct IO. Similarly the i_iolock cannot be taken inside a page fault because
* direct IO. Similarly the i_rwsem cannot be taken inside a page fault because
* page faults already hold the mmap_sem.
*
* Hence to serialise fully against both syscall and mmap based IO, we need to
* take both the i_iolock and the i_mmap_lock. These locks should *only* be both
* 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
* free manner (e.g. truncate, hole punch and other extent manipulation
* functions).
@ -191,10 +191,13 @@ xfs_ilock(
(XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0);
if (lock_flags & XFS_IOLOCK_EXCL)
mrupdate_nested(&ip->i_iolock, XFS_IOLOCK_DEP(lock_flags));
else if (lock_flags & XFS_IOLOCK_SHARED)
mraccess_nested(&ip->i_iolock, XFS_IOLOCK_DEP(lock_flags));
if (lock_flags & XFS_IOLOCK_EXCL) {
down_write_nested(&VFS_I(ip)->i_rwsem,
XFS_IOLOCK_DEP(lock_flags));
} else if (lock_flags & XFS_IOLOCK_SHARED) {
down_read_nested(&VFS_I(ip)->i_rwsem,
XFS_IOLOCK_DEP(lock_flags));
}
if (lock_flags & XFS_MMAPLOCK_EXCL)
mrupdate_nested(&ip->i_mmaplock, XFS_MMAPLOCK_DEP(lock_flags));
@ -240,10 +243,10 @@ xfs_ilock_nowait(
ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0);
if (lock_flags & XFS_IOLOCK_EXCL) {
if (!mrtryupdate(&ip->i_iolock))
if (!down_write_trylock(&VFS_I(ip)->i_rwsem))
goto out;
} else if (lock_flags & XFS_IOLOCK_SHARED) {
if (!mrtryaccess(&ip->i_iolock))
if (!down_read_trylock(&VFS_I(ip)->i_rwsem))
goto out;
}
@ -271,9 +274,9 @@ out_undo_mmaplock:
mrunlock_shared(&ip->i_mmaplock);
out_undo_iolock:
if (lock_flags & XFS_IOLOCK_EXCL)
mrunlock_excl(&ip->i_iolock);
up_write(&VFS_I(ip)->i_rwsem);
else if (lock_flags & XFS_IOLOCK_SHARED)
mrunlock_shared(&ip->i_iolock);
up_read(&VFS_I(ip)->i_rwsem);
out:
return 0;
}
@ -310,9 +313,9 @@ xfs_iunlock(
ASSERT(lock_flags != 0);
if (lock_flags & XFS_IOLOCK_EXCL)
mrunlock_excl(&ip->i_iolock);
up_write(&VFS_I(ip)->i_rwsem);
else if (lock_flags & XFS_IOLOCK_SHARED)
mrunlock_shared(&ip->i_iolock);
up_read(&VFS_I(ip)->i_rwsem);
if (lock_flags & XFS_MMAPLOCK_EXCL)
mrunlock_excl(&ip->i_mmaplock);
@ -345,7 +348,7 @@ xfs_ilock_demote(
if (lock_flags & XFS_MMAPLOCK_EXCL)
mrdemote(&ip->i_mmaplock);
if (lock_flags & XFS_IOLOCK_EXCL)
mrdemote(&ip->i_iolock);
downgrade_write(&VFS_I(ip)->i_rwsem);
trace_xfs_ilock_demote(ip, lock_flags, _RET_IP_);
}
@ -370,8 +373,9 @@ xfs_isilocked(
if (lock_flags & (XFS_IOLOCK_EXCL|XFS_IOLOCK_SHARED)) {
if (!(lock_flags & XFS_IOLOCK_SHARED))
return !!ip->i_iolock.mr_writer;
return rwsem_is_locked(&ip->i_iolock.mr_lock);
return !debug_locks ||
lockdep_is_held_type(&VFS_I(ip)->i_rwsem, 0);
return rwsem_is_locked(&VFS_I(ip)->i_rwsem);
}
ASSERT(0);
@ -421,11 +425,7 @@ xfs_lock_inumorder(int lock_mode, int subclass)
if (lock_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL)) {
ASSERT(subclass <= XFS_IOLOCK_MAX_SUBCLASS);
ASSERT(xfs_lockdep_subclass_ok(subclass +
XFS_IOLOCK_PARENT_VAL));
class += subclass << XFS_IOLOCK_SHIFT;
if (lock_mode & XFS_IOLOCK_PARENT)
class += XFS_IOLOCK_PARENT_VAL << XFS_IOLOCK_SHIFT;
}
if (lock_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)) {
@ -477,8 +477,6 @@ xfs_lock_inodes(
XFS_ILOCK_EXCL));
ASSERT(!(lock_mode & (XFS_IOLOCK_SHARED | XFS_MMAPLOCK_SHARED |
XFS_ILOCK_SHARED)));
ASSERT(!(lock_mode & XFS_IOLOCK_EXCL) ||
inodes <= XFS_IOLOCK_MAX_SUBCLASS + 1);
ASSERT(!(lock_mode & XFS_MMAPLOCK_EXCL) ||
inodes <= XFS_MMAPLOCK_MAX_SUBCLASS + 1);
ASSERT(!(lock_mode & XFS_ILOCK_EXCL) ||
@ -581,10 +579,8 @@ xfs_lock_two_inodes(
int attempts = 0;
xfs_log_item_t *lp;
if (lock_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL)) {
ASSERT(!(lock_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)));
ASSERT(!(lock_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)));
} else if (lock_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL))
ASSERT(!(lock_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL)));
if (lock_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL))
ASSERT(!(lock_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)));
ASSERT(ip0->i_ino != ip1->i_ino);
@ -715,7 +711,6 @@ xfs_lookup(
if (XFS_FORCED_SHUTDOWN(dp->i_mount))
return -EIO;
xfs_ilock(dp, XFS_IOLOCK_SHARED);
error = xfs_dir_lookup(NULL, dp, name, &inum, ci_name);
if (error)
goto out_unlock;
@ -724,14 +719,12 @@ xfs_lookup(
if (error)
goto out_free_name;
xfs_iunlock(dp, XFS_IOLOCK_SHARED);
return 0;
out_free_name:
if (ci_name)
kmem_free(ci_name->name);
out_unlock:
xfs_iunlock(dp, XFS_IOLOCK_SHARED);
*ipp = NULL;
return error;
}
@ -1215,8 +1208,7 @@ xfs_create(
if (error)
goto out_release_inode;
xfs_ilock(dp, XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL |
XFS_IOLOCK_PARENT | XFS_ILOCK_PARENT);
xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
unlock_dp_on_error = true;
xfs_defer_init(&dfops, &first_block);
@ -1252,7 +1244,7 @@ xfs_create(
* the transaction cancel unlocking dp so don't do it explicitly in the
* error path.
*/
xfs_trans_ijoin(tp, dp, XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, dp, XFS_ILOCK_EXCL);
unlock_dp_on_error = false;
error = xfs_dir_createname(tp, dp, name, ip->i_ino,
@ -1325,7 +1317,7 @@ xfs_create(
xfs_qm_dqrele(pdqp);
if (unlock_dp_on_error)
xfs_iunlock(dp, XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL);
xfs_iunlock(dp, XFS_ILOCK_EXCL);
return error;
}
@ -1466,11 +1458,10 @@ xfs_link(
if (error)
goto std_return;
xfs_ilock(tdp, XFS_IOLOCK_EXCL | XFS_IOLOCK_PARENT);
xfs_lock_two_inodes(sip, tdp, XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, sip, XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, tdp, XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, tdp, XFS_ILOCK_EXCL);
/*
* If we are using project inheritance, we only allow hard link
@ -2579,10 +2570,9 @@ xfs_remove(
goto std_return;
}
xfs_ilock(dp, XFS_IOLOCK_EXCL | XFS_IOLOCK_PARENT);
xfs_lock_two_inodes(dp, ip, XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, dp, XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, dp, XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
/*
@ -2963,12 +2953,6 @@ xfs_rename(
* whether the target directory is the same as the source
* directory, we can lock from 2 to 4 inodes.
*/
if (!new_parent)
xfs_ilock(src_dp, XFS_IOLOCK_EXCL | XFS_IOLOCK_PARENT);
else
xfs_lock_two_inodes(src_dp, target_dp,
XFS_IOLOCK_EXCL | XFS_IOLOCK_PARENT);
xfs_lock_inodes(inodes, num_inodes, XFS_ILOCK_EXCL);
/*
@ -2976,9 +2960,9 @@ xfs_rename(
* we can rely on either trans_commit or trans_cancel to unlock
* them.
*/
xfs_trans_ijoin(tp, src_dp, XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, src_dp, XFS_ILOCK_EXCL);
if (new_parent)
xfs_trans_ijoin(tp, target_dp, XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, target_dp, XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, src_ip, XFS_ILOCK_EXCL);
if (target_ip)
xfs_trans_ijoin(tp, target_ip, XFS_ILOCK_EXCL);