[Fwd: [PATCH 7/8] reiser4-try_capture_block-update.patch]
From: Hans Reiser
Date: Wed Nov 16 2005 - 03:58:04 EST
--- Begin Message ---
.
From: Alex Zarochentsev <zam@xxxxxxxxxxx>
try_capture_block:
avoid holding more than two spinlocks at a time.
avoid to capture at read requests if
the node wasn't captured before
wake_up_all_lopri_owners:
don't wake the same thread up twice
Cleanup.
Signed-off-by: Vladimir V. Saveliev <vs@xxxxxxxxxxx>
fs/reiser4/lock.c | 5
fs/reiser4/tree.c | 7
fs/reiser4/txnmgr.c | 630 ++++++++++------------------------------------------
3 files changed, 126 insertions(+), 516 deletions(-)
diff -puN fs/reiser4/lock.c~reiser4-try_capture_block-update fs/reiser4/lock.c
--- linux-2.6.14-mm2/fs/reiser4/lock.c~reiser4-try_capture_block-update 2005-11-15 17:19:58.000000000 +0300
+++ linux-2.6.14-mm2-vs/fs/reiser4/lock.c 2005-11-15 17:19:59.000000000 +0300
@@ -252,10 +252,9 @@ static void wake_up_all_lopri_owners(zno
if (!handle->signaled) {
handle->signaled = 1;
atomic_inc(&handle->owner->nr_signaled);
+ /* Wake up a single process */
+ __reiser4_wake_up(handle->owner);
}
- /* Wake up a single process */
- __reiser4_wake_up(handle->owner);
-
spin_unlock_stack(handle->owner);
}
}
diff -puN fs/reiser4/tree.c~reiser4-try_capture_block-update fs/reiser4/tree.c
--- linux-2.6.14-mm2/fs/reiser4/tree.c~reiser4-try_capture_block-update 2005-11-15 17:19:58.000000000 +0300
+++ linux-2.6.14-mm2-vs/fs/reiser4/tree.c 2005-11-15 17:19:59.000000000 +0300
@@ -792,13 +792,8 @@ void forget_znode(lock_handle * handle)
* invalidation does not allow other threads to waste cpu time is a busy
* loop, trying to lock dying object. The exception is in the flush
* code when we take node directly from atom's capture list.*/
-
- write_unlock_zlock(&node->lock);
- /* and, remove from atom's capture list. */
- uncapture_znode(node);
- write_lock_zlock(&node->lock);
-
invalidate_lock(handle);
+ uncapture_znode(node);
}
/* Check that internal item at @pointer really contains pointer to @child. */
diff -puN fs/reiser4/txnmgr.c~reiser4-try_capture_block-update fs/reiser4/txnmgr.c
--- linux-2.6.14-mm2/fs/reiser4/txnmgr.c~reiser4-try_capture_block-update 2005-11-15 17:19:58.000000000 +0300
+++ linux-2.6.14-mm2-vs/fs/reiser4/txnmgr.c 2005-11-15 17:19:59.000000000 +0300
@@ -253,24 +253,15 @@ static void capture_assign_txnh_nolock(t
static void capture_assign_block_nolock(txn_atom * atom, jnode * node);
-static int capture_assign_block(txn_handle * txnh, jnode * node);
-
-static int capture_assign_txnh(jnode * node, txn_handle * txnh,
- txn_capture mode, int can_coc);
-
static void fuse_not_fused_lock_owners(txn_handle * txnh, znode * node);
static int capture_init_fusion(jnode * node, txn_handle * txnh,
txn_capture mode, int can_coc);
-static int capture_fuse_wait(jnode * node, txn_handle * txnh, txn_atom * atomf,
- txn_atom * atomh, txn_capture mode);
+static int capture_fuse_wait(txn_handle *, txn_atom *, txn_atom *, txn_capture);
static void capture_fuse_into(txn_atom * small, txn_atom * large);
-static int capture_copy(jnode * node, txn_handle * txnh, txn_atom * atomf,
- txn_atom * atomh, txn_capture mode, int can_coc);
-
void invalidate_list(struct list_head *);
/* GENERIC STRUCTURES */
@@ -1865,158 +1856,99 @@ static int commit_txnh(txn_handle * txnh
released. The external interface (try_capture) manages re-aquiring the jnode lock
in the failure case.
*/
-static int
-try_capture_block(txn_handle * txnh, jnode * node, txn_capture mode,
- txn_atom ** atom_alloc, int can_coc)
+static int try_capture_block(
+ txn_handle * txnh, jnode * node, txn_capture mode,
+ txn_atom ** atom_alloc)
{
- int ret;
txn_atom *block_atom;
txn_atom *txnh_atom;
/* Should not call capture for READ_NONCOM requests, handled in try_capture. */
assert("jmacd-567", CAPTURE_TYPE(mode) != TXN_CAPTURE_READ_NONCOM);
- /* FIXME-ZAM-HANS: FIXME_LATER_JMACD Should assert that atom->tree == node->tree somewhere. */
-
+ /* FIXME-ZAM-HANS: FIXME_LATER_JMACD Should assert that atom->tree ==
+ * node->tree somewhere. */
assert("umka-194", txnh != NULL);
assert("umka-195", node != NULL);
/* The jnode is already locked! Being called from try_capture(). */
assert_spin_locked(&(node->guard));
-
block_atom = node->atom;
/* Get txnh spinlock, this allows us to compare txn_atom pointers but it doesn't
let us touch the atoms themselves. */
spin_lock_txnh(txnh);
-
txnh_atom = txnh->atom;
- if (txnh_atom != NULL && block_atom == txnh_atom) {
- spin_unlock_txnh(txnh);
- return 0;
- }
- /* NIKITA-HANS: nothing */
- if (txnh_atom != NULL) {
- /* It is time to perform deadlock prevention check over the
- node we want to capture. It is possible this node was
- locked for read without capturing it. The optimization
- which allows to do it helps us in keeping atoms independent
- as long as possible but it may cause lock/fuse deadlock
- problems.
-
- A number of similar deadlock situations with locked but not
- captured nodes were found. In each situation there are two
- or more threads: one of them does flushing while another
- one does routine balancing or tree lookup. The flushing
- thread (F) sleeps in long term locking request for node
- (N), another thread (A) sleeps in trying to capture some
- node already belonging the atom F, F has a state which
- prevents immediately fusion .
-
- Deadlocks of this kind cannot happen if node N was properly
- captured by thread A. The F thread fuse atoms before
- locking therefore current atom of thread F and current atom
- of thread A became the same atom and thread A may proceed.
- This does not work if node N was not captured because the
- fusion of atom does not happens.
-
- The following scheme solves the deadlock: If
- longterm_lock_znode locks and does not capture a znode,
- that znode is marked as MISSED_IN_CAPTURE. A node marked
- this way is processed by the code below which restores the
- missed capture and fuses current atoms of all the node lock
- owners by calling the fuse_not_fused_lock_owners()
- function.
- */
-
- if ( // txnh_atom->stage >= ASTAGE_CAPTURE_WAIT &&
- jnode_is_znode(node) && znode_is_locked(JZNODE(node))
- && JF_ISSET(node, JNODE_MISSED_IN_CAPTURE)) {
+ if (txnh_atom == NULL) {
+ if (block_atom == NULL) {
spin_unlock_txnh(txnh);
- JF_CLR(node, JNODE_MISSED_IN_CAPTURE);
spin_unlock_jnode(node);
- fuse_not_fused_lock_owners(txnh, JZNODE(node));
+ return atom_begin_and_assign_to_txnh(atom_alloc, txnh);
+ } else {
+ atomic_inc(&block_atom->refcount);
+ spin_unlock_jnode(node);
+ if (!spin_trylock_atom(block_atom)) {
+ spin_unlock_txnh(txnh);
+ spin_lock_atom(block_atom);
+ spin_lock_txnh(txnh);
+ }
+ if (node->atom != block_atom || txnh->atom != NULL) {
+ spin_unlock_txnh(txnh);
+ atom_dec_and_unlock(block_atom);
+ return RETERR(-E_REPEAT);
+ }
+ atomic_dec(&block_atom->refcount);
+ if (block_atom->stage > ASTAGE_CAPTURE_WAIT ||
+ (block_atom->stage == ASTAGE_CAPTURE_WAIT &&
+ block_atom->txnh_count != 0))
+ return capture_fuse_wait(txnh, block_atom, NULL, mode);
+ capture_assign_txnh_nolock(block_atom, txnh);
+ spin_unlock_txnh(txnh);
+ spin_unlock_atom(block_atom);
return RETERR(-E_REPEAT);
}
- }
-
- if (block_atom != NULL) {
- /* The block has already been assigned to an atom. */
-
- /* case (block_atom == txnh_atom) is already handled above */
- if (txnh_atom == NULL) {
-
- /* The txnh is unassigned, try to assign it. */
- ret = capture_assign_txnh(node, txnh, mode, can_coc);
- if (ret != 0) {
- /* E_REPEAT or otherwise */
- assert_spin_not_locked(&(txnh->hlock));
- assert_spin_not_locked(&(node->guard));
- return ret;
- }
-
- /* Either the txnh is now assigned to the block's atom or the read-request was
- granted because the block is committing. Locks still held. */
- } else {
- if (mode & TXN_CAPTURE_DONT_FUSE) {
+ } else {
+ if (JF_ISSET(node, JNODE_MISSED_IN_CAPTURE)) {
+ JF_CLR(node, JNODE_MISSED_IN_CAPTURE);
+ if (jnode_is_znode(node) && znode_is_locked(JZNODE(node))) {
spin_unlock_txnh(txnh);
spin_unlock_jnode(node);
- /* we are in a "no-fusion" mode and @node is
- * already part of transaction. */
- return RETERR(-E_NO_NEIGHBOR);
- }
- /* In this case, both txnh and node belong to different atoms. This function
- returns -E_REPEAT on successful fusion, 0 on the fall-through case. */
- ret = capture_init_fusion(node, txnh, mode, can_coc);
- if (ret != 0) {
- assert_spin_not_locked(&(txnh->hlock));
- assert_spin_not_locked(&(node->guard));
- return ret;
+ fuse_not_fused_lock_owners(txnh, JZNODE(node));
+ return RETERR(-E_REPEAT);
}
-
- /* The fall-through case is read request for committing block. Locks still
- held. */
}
-
- } else if ((mode & TXN_CAPTURE_WTYPES) != 0) {
-
- /* In this case, the page is unlocked and the txnh wishes exclusive access. */
-
- if (txnh_atom != NULL) {
- /* The txnh is already assigned: add the page to its atom. */
- ret = capture_assign_block(txnh, node);
- if (ret != 0) {
- /* E_REPEAT or otherwise */
- assert_spin_not_locked(&(txnh->hlock));
- assert_spin_not_locked(&(node->guard));
- return ret;
+ if (block_atom == NULL) {
+ atomic_inc(&txnh_atom->refcount);
+ spin_unlock_txnh(txnh);
+ if (!spin_trylock_atom(txnh_atom)) {
+ spin_unlock_jnode(node);
+ spin_lock_atom(txnh_atom);
+ spin_lock_jnode(node);
}
-
- /* Success: Locks are still held. */
-
+ if (txnh->atom != txnh_atom || node->atom != NULL
+ || JF_ISSET(node, JNODE_IS_DYING)) {
+ spin_unlock_jnode(node);
+ atom_dec_and_unlock(txnh_atom);
+ return RETERR(-E_REPEAT);
+ }
+ atomic_dec(&txnh_atom->refcount);
+ capture_assign_block_nolock(txnh_atom, node);
+ spin_unlock_atom(txnh_atom);
} else {
-
- /* In this case, neither txnh nor page are assigned to
- * an atom. */
- spin_unlock_jnode(node);
+ if (txnh_atom != block_atom) {
+ if (mode & TXN_CAPTURE_DONT_FUSE) {
+ spin_unlock_txnh(txnh);
+ spin_unlock_jnode(node);
+ /* we are in a "no-fusion" mode and @node is
+ * already part of transaction. */
+ return RETERR(-E_NO_NEIGHBOR);
+ }
+ return capture_init_fusion(node, txnh, mode, 1);
+ }
spin_unlock_txnh(txnh);
- return atom_begin_and_assign_to_txnh(atom_alloc, txnh);
}
-
- } else {
- /* The jnode is uncaptured and its a read request -- fine. */
- assert("jmacd-411",
- CAPTURE_TYPE(mode) == TXN_CAPTURE_READ_ATOMIC);
}
-
- /* Successful case: both jnode and txnh are still locked. */
- assert_spin_locked(&(txnh->hlock));
- assert_spin_locked(&(node->guard));
-
- /* Release txnh lock, return with the jnode still locked. */
- spin_unlock_txnh(txnh);
-
return 0;
}
@@ -2048,10 +1980,6 @@ build_capture_mode(jnode * node, znode_l
/* In this case (read lock at a non-leaf) there's no reason to
* capture. */
/* cap_mode = TXN_CAPTURE_READ_NONCOM; */
-
- /* Mark this node as "MISSED". It helps in further deadlock
- * analysis */
- JF_SET(node, JNODE_MISSED_IN_CAPTURE);
return 0;
}
@@ -2072,33 +2000,32 @@ build_capture_mode(jnode * node, znode_l
cannot be processed immediately as it was requested in flags,
< 0 - other errors.
*/
-int
-try_capture(jnode * node, znode_lock_mode lock_mode,
- txn_capture flags, int can_coc)
+int try_capture(jnode * node, znode_lock_mode lock_mode,
+ txn_capture flags, int can_coc)
{
txn_atom *atom_alloc = NULL;
txn_capture cap_mode;
txn_handle *txnh = get_current_context()->trans;
-#if REISER4_COPY_ON_CAPTURE
- int coc_enabled = 1;
-#endif
int ret;
assert_spin_locked(&(node->guard));
repeat:
+ if (JF_ISSET(node, JNODE_IS_DYING))
+ return RETERR(-EINVAL);
+ if (node->atom != NULL && txnh->atom == node->atom)
+ return 0;
cap_mode = build_capture_mode(node, lock_mode, flags);
- if (cap_mode == 0)
+ if (cap_mode == 0 ||
+ (!(cap_mode & TXN_CAPTURE_WTYPES) && node->atom == NULL)) {
+ /* Mark this node as "MISSED". It helps in further deadlock
+ * analysis */
+ if (jnode_is_znode(node))
+ JF_SET(node, JNODE_MISSED_IN_CAPTURE);
return 0;
-
+ }
/* Repeat try_capture as long as -E_REPEAT is returned. */
-#if REISER4_COPY_ON_CAPTURE
- ret = try_capture_block(txnh, node, cap_mode, &atom_alloc, can_coc
- && coc_enabled);
- coc_enabled = 1;
-#else
- ret = try_capture_block(txnh, node, cap_mode, &atom_alloc, can_coc);
-#endif
+ ret = try_capture_block(txnh, node, cap_mode, &atom_alloc);
/* Regardless of non_blocking:
If ret == 0 then jnode is still locked.
@@ -2182,6 +2109,14 @@ try_capture(jnode * node, znode_lock_mod
return ret;
}
+static void release_two_atoms(txn_atom *one, txn_atom *two)
+{
+ spin_unlock_atom(one);
+ atom_dec_and_unlock(two);
+ spin_lock_atom(one);
+ atom_dec_and_unlock(one);
+}
+
/* This function sets up a call to try_capture_block and repeats as long as -E_REPEAT is
returned by that routine. The txn_capture request mode is computed here depending on
the transaction handle's type and the lock request. This is called from the depths of
@@ -2256,10 +2191,7 @@ static void fuse_not_fused_lock_owners(t
spin_lock_atom(atomh);
}
if (atomh == atomf || !atom_isopen(atomh) || !atom_isopen(atomf)) {
- spin_unlock_atom(atomf);
- atom_dec_and_unlock(atomh);
- spin_lock_atom(atomf);
- atom_dec_and_unlock(atomf);
+ release_two_atoms(atomf, atomh);
goto repeat;
}
atomic_dec(&atomh->refcount);
@@ -2843,221 +2775,6 @@ void unformatted_make_reloc(jnode * node
mark_jnode_queued(fq, node);
}
-static int trylock_wait(txn_atom * atom, txn_handle * txnh, jnode * node)
-{
- if (unlikely(!spin_trylock_atom(atom))) {
- atomic_inc(&atom->refcount);
-
- spin_unlock_jnode(node);
- spin_unlock_txnh(txnh);
-
- spin_lock_atom(atom);
- /* caller should eliminate extra reference by calling
- * atom_dec_and_unlock() for this atom. */
- return 1;
- } else
- return 0;
-}
-
-/*
- * in transaction manager jnode spin lock and transaction handle spin lock
- * nest within atom spin lock. During capturing we are in a situation when
- * jnode and transaction handle spin locks are held and we want to manipulate
- * atom's data (capture lists, and txnh list) to add node and/or handle to the
- * atom. Releasing jnode (or txnh) spin lock at this point is unsafe, because
- * concurrent fusion can render assumption made by capture so far (about
- * ->atom pointers in jnode and txnh) invalid. Initial code used try-lock and
- * if atom was busy returned -E_REPEAT to the top level. This can lead to the
- * busy loop if atom is locked for long enough time. Function below tries to
- * throttle this loop.
- *
- */
-/* ZAM-FIXME-HANS: how feasible would it be to use our hi-lo priority locking
- mechanisms/code for this as well? Does that make any sense? */
-/* ANSWER(Zam): I am not sure that I understand you proposal right, but the idea
- might be in inventing spin_lock_lopri() which should be a complex loop with
- "release lock" messages check like we have in the znode locking. I think we
- should not substitute spin locks by more complex busy loops. Once it was
- done that way in try_capture_block() where spin lock waiting was spread in a
- busy loop through several functions. The proper solution should be in
- making spin lock contention rare. */
-static int trylock_throttle(txn_atom * atom, txn_handle * txnh, jnode * node)
-{
- assert("nikita-3224", atom != NULL);
- assert("nikita-3225", txnh != NULL);
- assert("nikita-3226", node != NULL);
-
- assert_spin_locked(&(txnh->hlock));
- assert_spin_locked(&(node->guard));
-
- if (unlikely(trylock_wait(atom, txnh, node) != 0)) {
- atom_dec_and_unlock(atom);
- return RETERR(-E_REPEAT);
- } else
- return 0;
-}
-
-/* This function assigns a block to an atom, but first it must obtain the atom lock. If
- the atom lock is busy, it returns -E_REPEAT to avoid deadlock with a fusing atom. Since
- the transaction handle is currently open, we know the atom must also be open. */
-static int capture_assign_block(txn_handle * txnh, jnode * node)
-{
- txn_atom *atom;
- int result;
-
- assert("umka-206", txnh != NULL);
- assert("umka-207", node != NULL);
-
- atom = txnh->atom;
-
- assert("umka-297", atom != NULL);
-
- result = trylock_throttle(atom, txnh, node);
- if (result != 0) {
- /* this avoid busy loop, but we return -E_REPEAT anyway to
- * simplify things. */
- return result;
- } else {
- assert("jmacd-19", atom_isopen(atom));
-
- /* Add page to capture list. */
- capture_assign_block_nolock(atom, node);
-
- /* Success holds onto jnode & txnh locks. Unlock atom. */
- spin_unlock_atom(atom);
- return 0;
- }
-}
-
-/* This function assigns a handle to an atom, but first it must obtain the atom lock. If
- the atom is busy, it returns -E_REPEAT to avoid deadlock with a fusing atom. Unlike
- capture_assign_block, the atom may be closed but we cannot know this until the atom is
- locked. If the atom is closed and the request is to read, it is as if the block is
- unmodified and the request is satisified without actually assigning the transaction
- handle. If the atom is closed and the handle requests to write the block, then
- initiate copy-on-capture.
-*/
-static int
-capture_assign_txnh(jnode * node, txn_handle * txnh, txn_capture mode,
- int can_coc)
-{
- txn_atom *atom;
-
- assert("umka-208", node != NULL);
- assert("umka-209", txnh != NULL);
-
- atom = node->atom;
-
- assert("umka-298", atom != NULL);
-
- /*
- * optimization: this code went through three evolution stages. Main
- * driving force of evolution here is lock ordering:
- *
- * at the entry to this function following pre-conditions are met:
- *
- * 1. txnh and node are both spin locked,
- *
- * 2. node belongs to atom, and
- *
- * 3. txnh don't.
- *
- * What we want to do here is to acquire spin lock on node's atom and
- * modify it somehow depending on its ->stage. In the simplest case,
- * where ->stage is ASTAGE_CAPTURE_FUSE, txnh should be added to
- * atom's list. Problem is that atom spin lock nests outside of jnode
- * and transaction handle ones. So, we cannot just spin_lock_atom here.
- *
- * Solutions tried here:
- *
- * 1. spin_trylock(atom), return -E_REPEAT on failure.
- *
- * 2. spin_trylock(atom). On failure to acquire lock, increment
- * atom->refcount, release all locks, and spin on atom lock. Then
- * decrement ->refcount, unlock atom and return -E_REPEAT.
- *
- * 3. like previous one, but before unlocking atom, re-acquire
- * spin locks on node and txnh and re-check whether function
- * pre-condition are still met. Continue boldly if they are.
- *
- */
- if (trylock_wait(atom, txnh, node) != 0) {
- spin_lock_jnode(node);
- spin_lock_txnh(txnh);
- /* NOTE-NIKITA is it at all possible that current txnh
- * spontaneously changes ->atom from NULL to non-NULL? */
- if (node->atom == NULL ||
- txnh->atom != NULL || atom != node->atom) {
- /* something changed. Caller have to re-decide */
- spin_unlock_txnh(txnh);
- spin_unlock_jnode(node);
- atom_dec_and_unlock(atom);
- return RETERR(-E_REPEAT);
- } else {
- /* atom still has a jnode on its list (node->atom ==
- * atom), it means atom is not fused or finished
- * (committed), we can safely decrement its refcount
- * because it is not a last reference. */
- atomic_dec(&atom->refcount);
- assert("zam-990", atomic_read(&atom->refcount) > 0);
- }
- }
-
- if (atom->stage == ASTAGE_CAPTURE_WAIT &&
- (atom->txnh_count != 0 ||
- atom_should_commit(atom) || atom_should_commit_asap(atom))) {
- /* We don't fuse with the atom in ASTAGE_CAPTURE_WAIT only if
- * there is open transaction handler. It makes sense: those
- * atoms should not wait ktxnmgrd to flush and commit them.
- * And, it solves deadlocks with loop back devices (reiser4 over
- * loopback over reiser4), when ktxnmrgd is busy committing one
- * atom (above the loop back device) and can't flush an atom
- * below the loopback. */
-
- /* The atom could be blocking requests--this is the first chance we've had
- to test it. Since this txnh is not yet assigned, the fuse_wait logic
- is not to avoid deadlock, its just waiting. Releases all three locks
- and returns E_REPEAT. */
-
- return capture_fuse_wait(node, txnh, atom, NULL, mode);
-
- } else if (atom->stage > ASTAGE_CAPTURE_WAIT) {
-
- /* The block is involved with a committing atom. */
- if (CAPTURE_TYPE(mode) == TXN_CAPTURE_READ_ATOMIC) {
-
- /* A read request for a committing block can be satisfied w/o
- COPY-ON-CAPTURE. */
-
- /* Success holds onto the jnode & txnh lock. Continue to unlock
- atom below. */
-
- } else {
-
- /* Perform COPY-ON-CAPTURE. Copy and try again. This function
- releases all three locks. */
- return capture_copy(node, txnh, atom, NULL, mode,
- can_coc);
- }
-
- } else {
-
- assert("jmacd-160", atom->stage == ASTAGE_CAPTURE_FUSE ||
- (atom->stage == ASTAGE_CAPTURE_WAIT
- && atom->txnh_count == 0));
-
- /* Add txnh to active list. */
- capture_assign_txnh_nolock(atom, txnh);
-
- /* Success holds onto the jnode & txnh lock. Continue to unlock atom
- below. */
- }
-
- /* Unlock the atom */
- spin_unlock_atom(atom);
- return 0;
-}
-
int capture_super_block(struct super_block *s)
{
int result;
@@ -3142,20 +2859,15 @@ static int wait_for_fusion(txn_atom * at
Lock ordering in this method: all four locks are held: JNODE_LOCK, TXNH_LOCK,
BOTH_ATOM_LOCKS. Result: all four locks are released.
*/
-static int
-capture_fuse_wait(jnode * node, txn_handle * txnh, txn_atom * atomf,
- txn_atom * atomh, txn_capture mode)
+static int capture_fuse_wait(txn_handle * txnh, txn_atom * atomf,
+ txn_atom * atomh, txn_capture mode)
{
int ret;
txn_wait_links wlinks;
- assert("umka-212", node != NULL);
assert("umka-213", txnh != NULL);
assert("umka-214", atomf != NULL);
- /* We do not need the node lock. */
- spin_unlock_jnode(node);
-
if ((mode & TXN_CAPTURE_NONBLOCKING) != 0) {
spin_unlock_txnh(txnh);
spin_unlock_atom(atomf);
@@ -3204,84 +2916,24 @@ capture_fuse_wait(jnode * node, txn_hand
list_del(&wlinks._fwaiting_link);
atom_dec_and_unlock(atomh);
}
-#if REISER4_DEBUG
- if (ret)
- assert_spin_not_locked(&(node->guard));
-#endif
return ret;
}
-static inline int
-capture_init_fusion_locked(jnode * node, txn_handle * txnh, txn_capture mode,
- int can_coc)
-{
- txn_atom *atomf;
- txn_atom *atomh;
-
- assert("umka-216", txnh != NULL);
- assert("umka-217", node != NULL);
-
- atomh = txnh->atom;
- atomf = node->atom;
-
- /* The txnh atom must still be open (since the txnh is active)... the node atom may
- be in some later stage (checked next). */
- assert("jmacd-20", atom_isopen(atomh));
-
- /* If the node atom is in the FUSE_WAIT state then we should wait, except to
- avoid deadlock we still must fuse if the txnh atom is also in FUSE_WAIT. */
- if (atomf->stage == ASTAGE_CAPTURE_WAIT &&
- atomh->stage != ASTAGE_CAPTURE_WAIT &&
- (atomf->txnh_count != 0 ||
- atom_should_commit(atomf) || atom_should_commit_asap(atomf))) {
- /* see comment in capture_assign_txnh() about the
- * "atomf->txnh_count != 0" condition. */
- /* This unlocks all four locks and returns E_REPEAT. */
- return capture_fuse_wait(node, txnh, atomf, atomh, mode);
-
- } else if (atomf->stage > ASTAGE_CAPTURE_WAIT) {
-
- /* The block is involved with a comitting atom. */
- if (CAPTURE_TYPE(mode) == TXN_CAPTURE_READ_ATOMIC) {
- /* A read request for a committing block can be satisfied w/o
- COPY-ON-CAPTURE. Success holds onto the jnode & txnh
- locks. */
- spin_unlock_atom(atomf);
- spin_unlock_atom(atomh);
- return 0;
- } else {
- /* Perform COPY-ON-CAPTURE. Copy and try again. This function
- releases all four locks. */
- return capture_copy(node, txnh, atomf, atomh, mode,
- can_coc);
- }
- }
-
- /* Because atomf's stage <= CAPTURE_WAIT */
- assert("jmacd-175", atom_isopen(atomf));
-
- /* If we got here its either because the atomh is in CAPTURE_WAIT or because the
- atomf is not in CAPTURE_WAIT. */
- assert("jmacd-176",
- (atomh->stage == ASTAGE_CAPTURE_WAIT
- || atomf->stage != ASTAGE_CAPTURE_WAIT)
- || atomf->txnh_count == 0);
-
- /* Now release the txnh lock: only holding the atoms at this point. */
- spin_unlock_txnh(txnh);
- spin_unlock_jnode(node);
+static void lock_two_atoms(txn_atom * one, txn_atom * two)
+{
+ assert("zam-1067", one != two);
- /* Decide which should be kept and which should be merged. */
- if (atom_pointer_count(atomf) < atom_pointer_count(atomh)) {
- capture_fuse_into(atomf, atomh);
+ /* lock the atom with lesser address first */
+ if (one < two) {
+ spin_lock_atom(one);
+ spin_lock_atom(two);
} else {
- capture_fuse_into(atomh, atomf);
+ spin_lock_atom(two);
+ spin_lock_atom(one);
}
-
- /* Atoms are unlocked in capture_fuse_into. No locks held. */
- return RETERR(-E_REPEAT);
}
+
/* Perform the necessary work to prepare for fusing two atoms, which involves
* acquiring two atom locks in the proper order. If one of the node's atom is
* blocking fusion (i.e., it is in the CAPTURE_WAIT stage) and the handle's
@@ -3294,19 +2946,34 @@ static int
capture_init_fusion(jnode * node, txn_handle * txnh, txn_capture mode,
int can_coc)
{
- /* Have to perform two trylocks here. */
- if (likely(spin_trylock_atom(node->atom))) {
- if (likely(spin_trylock_atom(txnh->atom)))
- return capture_init_fusion_locked(node, txnh, mode,
- can_coc);
- else {
- spin_unlock_atom(node->atom);
- }
- }
+ txn_atom * txnh_atom = txnh->atom;
+ txn_atom * block_atom = node->atom;
+
+ atomic_inc(&txnh_atom->refcount);
+ atomic_inc(&block_atom->refcount);
- spin_unlock_jnode(node);
spin_unlock_txnh(txnh);
- return RETERR(-E_REPEAT);
+ spin_unlock_jnode(node);
+
+ lock_two_atoms(txnh_atom, block_atom);
+
+ if (txnh->atom != txnh_atom || node->atom != block_atom ) {
+ release_two_atoms(txnh_atom, block_atom);
+ return RETERR(-E_REPEAT);
+ }
+
+ atomic_dec(&txnh_atom->refcount);
+ atomic_dec(&block_atom->refcount);
+
+ assert ("zam-1066", atom_isopen(txnh_atom));
+
+ if (txnh_atom->stage >= block_atom->stage ||
+ (block_atom->stage == ASTAGE_CAPTURE_WAIT && block_atom->txnh_count == 0)) {
+ capture_fuse_into(txnh_atom, block_atom);
+ return RETERR(-E_REPEAT);
+ }
+ spin_lock_txnh(txnh);
+ return capture_fuse_wait(txnh, block_atom, txnh_atom, mode);
}
/* This function splices together two jnode lists (small and large) and sets all jnodes in
@@ -4035,57 +3702,6 @@ static int create_copy_and_replace(jnode
}
#endif /* REISER4_COPY_ON_CAPTURE */
-/* Perform copy-on-capture of a block. */
-static int
-capture_copy(jnode * node, txn_handle * txnh, txn_atom * atomf,
- txn_atom * atomh, txn_capture mode, int can_coc)
-{
-#if REISER4_COPY_ON_CAPTURE
- reiser4_stat_inc(coc.calls);
-
- /* do not copy on capture in ent thread to avoid deadlock on coc semaphore */
- if (can_coc && get_current_context()->entd == 0) {
- int result;
-
- ON_TRACE(TRACE_TXN, "capture_copy\n");
-
- /* The txnh and its (possibly NULL) atom's locks are not needed
- at this point. */
- spin_unlock_txnh(txnh);
- if (atomh != NULL)
- spin_unlock_atom(atomh);
-
- /* create a copy of node, detach node from atom and attach its copy
- instead */
- atomic_inc(&atomf->refcount);
- result = create_copy_and_replace(node, atomf);
- assert("nikita-3474", schedulable());
- preempt_point();
- spin_lock_atom(atomf);
- atom_dec_and_unlock(atomf);
- preempt_point();
-
- if (result == 0) {
- if (jnode_is_znode(node)) {
- znode *z;
-
- z = JZNODE(node);
- z->version =
- znode_build_version(jnode_get_tree(node));
- }
- result = RETERR(-E_REPEAT);
- }
- return result;
- }
-
- reiser4_stat_inc(coc.forbidden);
- return capture_fuse_wait(node, txnh, atomf, atomh, mode);
-#else
- return capture_fuse_wait(node, txnh, atomf, atomh, mode);
-
-#endif
-}
-
/* Release a block from the atom, reversing the effects of being captured,
do not release atom's reference to jnode due to holding spin-locks.
Currently this is only called when the atom commits.
_
--- End Message ---