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authorDave Chinner <dchinner@redhat.com>2015-08-19 10:32:49 +1000
committerDave Chinner <david@fromorbit.com>2015-08-19 10:32:49 +1000
commit0952c8183c1575a78dc416b5e168987ff98728bb (patch)
treef9a583446e2e31fdb4eb15fb7d14701a8db6cdc0 /fs/xfs/xfs_inode.c
parent7df1c170b9a45ab3a7401c79bbefa9939bf8eafb (diff)
downloadlinux-0952c8183c1575a78dc416b5e168987ff98728bb.tar.bz2
xfs: clean up inode lockdep annotations
Lockdep annotations are a maintenance nightmare. Locking has to be modified to suit the limitations of the annotations, and we're always having to fix the annotations because they are unable to express the complexity of locking heirarchies correctly. So, next up, we've got more issues with lockdep annotations for inode locking w.r.t. XFS_LOCK_PARENT: - lockdep classes are exclusive and can't be ORed together to form new classes. - IOLOCK needs multiple PARENT subclasses to express the changes needed for the readdir locking rework needed to stop the endless flow of lockdep false positives involving readdir calling filldir under the ILOCK. - there are only 8 unique lockdep subclasses available, so we can't create a generic solution. IOWs we need to treat the 3-bit space available to each lock type differently: - IOLOCK uses xfs_lock_two_inodes(), so needs: - at least 2 IOLOCK subclasses - at least 2 IOLOCK_PARENT subclasses - MMAPLOCK uses xfs_lock_two_inodes(), so needs: - at least 2 MMAPLOCK subclasses - ILOCK uses xfs_lock_inodes with up to 5 inodes, so needs: - at least 5 ILOCK subclasses - one ILOCK_PARENT subclass - one RTBITMAP subclass - one RTSUM subclass For the IOLOCK, split the space into two sets of subclasses. For the MMAPLOCK, just use half the space for the one subclass to match the non-parent lock classes of the IOLOCK. For the ILOCK, use 0-4 as the ILOCK subclasses, 5-7 for the remaining individual subclasses. Because they are now all different, modify xfs_lock_inumorder() to handle the nested subclasses, and to assert fail if passed an invalid subclass. Further, annotate xfs_lock_inodes() to assert fail if an invalid combination of lock primitives and inode counts are passed that would result in a lockdep subclass annotation overflow. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
Diffstat (limited to 'fs/xfs/xfs_inode.c')
-rw-r--r--fs/xfs/xfs_inode.c68
1 files changed, 51 insertions, 17 deletions
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 3e343c7f347a..657f6123b445 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -164,7 +164,7 @@ xfs_ilock(
(XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL));
ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
(XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
- ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_DEP_MASK)) == 0);
+ 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));
@@ -212,7 +212,7 @@ xfs_ilock_nowait(
(XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL));
ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
(XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
- ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_DEP_MASK)) == 0);
+ ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0);
if (lock_flags & XFS_IOLOCK_EXCL) {
if (!mrtryupdate(&ip->i_iolock))
@@ -281,7 +281,7 @@ xfs_iunlock(
(XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL));
ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
(XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
- ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_DEP_MASK)) == 0);
+ ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0);
ASSERT(lock_flags != 0);
if (lock_flags & XFS_IOLOCK_EXCL)
@@ -364,30 +364,38 @@ int xfs_lock_delays;
/*
* Bump the subclass so xfs_lock_inodes() acquires each lock with a different
- * value. This shouldn't be called for page fault locking, but we also need to
- * ensure we don't overrun the number of lockdep subclasses for the iolock or
- * mmaplock as that is limited to 12 by the mmap lock lockdep annotations.
+ * value. This can be called for any type of inode lock combination, including
+ * parent locking. Care must be taken to ensure we don't overrun the subclass
+ * storage fields in the class mask we build.
*/
static inline int
xfs_lock_inumorder(int lock_mode, int subclass)
{
+ int class = 0;
+
+ ASSERT(!(lock_mode & (XFS_ILOCK_PARENT | XFS_ILOCK_RTBITMAP |
+ XFS_ILOCK_RTSUM)));
+
if (lock_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL)) {
- ASSERT(subclass + XFS_LOCK_INUMORDER <
- (1 << (XFS_MMAPLOCK_SHIFT - XFS_IOLOCK_SHIFT)));
- lock_mode |= (subclass + XFS_LOCK_INUMORDER) << XFS_IOLOCK_SHIFT;
+ ASSERT(subclass <= XFS_IOLOCK_MAX_SUBCLASS);
+ ASSERT(subclass + XFS_IOLOCK_PARENT_VAL <
+ MAX_LOCKDEP_SUBCLASSES);
+ 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)) {
- ASSERT(subclass + XFS_LOCK_INUMORDER <
- (1 << (XFS_ILOCK_SHIFT - XFS_MMAPLOCK_SHIFT)));
- lock_mode |= (subclass + XFS_LOCK_INUMORDER) <<
- XFS_MMAPLOCK_SHIFT;
+ ASSERT(subclass <= XFS_MMAPLOCK_MAX_SUBCLASS);
+ class += subclass << XFS_MMAPLOCK_SHIFT;
}
- if (lock_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL))
- lock_mode |= (subclass + XFS_LOCK_INUMORDER) << XFS_ILOCK_SHIFT;
+ if (lock_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)) {
+ ASSERT(subclass <= XFS_ILOCK_MAX_SUBCLASS);
+ class += subclass << XFS_ILOCK_SHIFT;
+ }
- return lock_mode;
+ return (lock_mode & ~XFS_LOCK_SUBCLASS_MASK) | class;
}
/*
@@ -399,6 +407,11 @@ xfs_lock_inumorder(int lock_mode, int subclass)
* transaction (such as truncate). This can result in deadlock since the long
* running trans might need to wait for the inode we just locked in order to
* push the tail and free space in the log.
+ *
+ * xfs_lock_inodes() can only be used to lock one type of lock at a time -
+ * the iolock, the mmaplock or the ilock, but not more than one at a time. If we
+ * lock more than one at a time, lockdep will report false positives saying we
+ * have violated locking orders.
*/
void
xfs_lock_inodes(
@@ -409,8 +422,29 @@ xfs_lock_inodes(
int attempts = 0, i, j, try_lock;
xfs_log_item_t *lp;
- /* currently supports between 2 and 5 inodes */
+ /*
+ * Currently supports between 2 and 5 inodes with exclusive locking. We
+ * support an arbitrary depth of locking here, but absolute limits on
+ * inodes depend on the the type of locking and the limits placed by
+ * lockdep annotations in xfs_lock_inumorder. These are all checked by
+ * the asserts.
+ */
ASSERT(ips && inodes >= 2 && inodes <= 5);
+ ASSERT(lock_mode & (XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL |
+ 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) ||
+ inodes <= XFS_ILOCK_MAX_SUBCLASS + 1);
+
+ if (lock_mode & XFS_IOLOCK_EXCL) {
+ ASSERT(!(lock_mode & (XFS_MMAPLOCK_EXCL | XFS_ILOCK_EXCL)));
+ } else if (lock_mode & XFS_MMAPLOCK_EXCL)
+ ASSERT(!(lock_mode & XFS_ILOCK_EXCL));
try_lock = 0;
i = 0;