From f057f6cdf64175db1151b1f5d110e29904f119a1 Mon Sep 17 00:00:00 2001 From: Steven Whitehouse Date: Mon, 12 Jan 2009 10:43:39 +0000 Subject: GFS2: Merge lock_dlm module into GFS2 This is the big patch that I've been working on for some time now. There are many reasons for wanting to make this change such as: o Reducing overhead by eliminating duplicated fields between structures o Simplifcation of the code (reduces the code size by a fair bit) o The locking interface is now the DLM interface itself as proposed some time ago. o Fewer lookups of glocks when processing replies from the DLM o Fewer memory allocations/deallocations for each glock o Scope to do further optimisations in the future (but this patch is more than big enough for now!) Please note that (a) this patch relates to the lock_dlm module and not the DLM itself, that is still a separate module; and (b) that we retain the ability to build GFS2 as a standalone single node filesystem with out requiring the DLM. This patch needs a lot of testing, hence my keeping it I restarted my -git tree after the last merge window. That way, this has the maximum exposure before its merged. This is (modulo a few minor bug fixes) the same patch that I've been posting on and off the the last three months and its passed a number of different tests so far. Signed-off-by: Steven Whitehouse --- fs/gfs2/glock.c | 249 +++++++++++++++++--------------------------------------- 1 file changed, 75 insertions(+), 174 deletions(-) (limited to 'fs/gfs2/glock.c') diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index 6b983aef785d..cd200a564c79 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -10,7 +10,6 @@ #include #include #include -#include #include #include #include @@ -18,7 +17,6 @@ #include #include #include -#include #include #include #include @@ -155,13 +153,10 @@ static void glock_free(struct gfs2_glock *gl) struct gfs2_sbd *sdp = gl->gl_sbd; struct inode *aspace = gl->gl_aspace; - if (sdp->sd_lockstruct.ls_ops->lm_put_lock) - sdp->sd_lockstruct.ls_ops->lm_put_lock(gl->gl_lock); - if (aspace) gfs2_aspace_put(aspace); - kmem_cache_free(gfs2_glock_cachep, gl); + sdp->sd_lockstruct.ls_ops->lm_put_lock(gfs2_glock_cachep, gl); } /** @@ -211,7 +206,6 @@ int gfs2_glock_put(struct gfs2_glock *gl) atomic_dec(&lru_count); } spin_unlock(&lru_lock); - GLOCK_BUG_ON(gl, gl->gl_state != LM_ST_UNLOCKED); GLOCK_BUG_ON(gl, !list_empty(&gl->gl_lru)); GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders)); glock_free(gl); @@ -255,27 +249,6 @@ static struct gfs2_glock *search_bucket(unsigned int hash, return NULL; } -/** - * gfs2_glock_find() - Find glock by lock number - * @sdp: The GFS2 superblock - * @name: The lock name - * - * Returns: NULL, or the struct gfs2_glock with the requested number - */ - -static struct gfs2_glock *gfs2_glock_find(const struct gfs2_sbd *sdp, - const struct lm_lockname *name) -{ - unsigned int hash = gl_hash(sdp, name); - struct gfs2_glock *gl; - - read_lock(gl_lock_addr(hash)); - gl = search_bucket(hash, sdp, name); - read_unlock(gl_lock_addr(hash)); - - return gl; -} - /** * may_grant - check if its ok to grant a new lock * @gl: The glock @@ -523,7 +496,7 @@ out_locked: } static unsigned int gfs2_lm_lock(struct gfs2_sbd *sdp, void *lock, - unsigned int cur_state, unsigned int req_state, + unsigned int req_state, unsigned int flags) { int ret = LM_OUT_ERROR; @@ -532,7 +505,7 @@ static unsigned int gfs2_lm_lock(struct gfs2_sbd *sdp, void *lock, return req_state == LM_ST_UNLOCKED ? 0 : req_state; if (likely(!test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) - ret = sdp->sd_lockstruct.ls_ops->lm_lock(lock, cur_state, + ret = sdp->sd_lockstruct.ls_ops->lm_lock(lock, req_state, flags); return ret; } @@ -575,7 +548,7 @@ __acquires(&gl->gl_spin) gl->gl_state == LM_ST_DEFERRED) && !(lck_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))) lck_flags |= LM_FLAG_TRY_1CB; - ret = gfs2_lm_lock(sdp, gl->gl_lock, gl->gl_state, target, lck_flags); + ret = gfs2_lm_lock(sdp, gl, target, lck_flags); if (!(ret & LM_OUT_ASYNC)) { finish_xmote(gl, ret); @@ -681,18 +654,6 @@ static void glock_work_func(struct work_struct *work) gfs2_glock_put(gl); } -static int gfs2_lm_get_lock(struct gfs2_sbd *sdp, struct lm_lockname *name, - void **lockp) -{ - int error = -EIO; - if (!sdp->sd_lockstruct.ls_ops->lm_get_lock) - return 0; - if (likely(!test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) - error = sdp->sd_lockstruct.ls_ops->lm_get_lock( - sdp->sd_lockstruct.ls_lockspace, name, lockp); - return error; -} - /** * gfs2_glock_get() - Get a glock, or create one if one doesn't exist * @sdp: The GFS2 superblock @@ -736,6 +697,9 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number, gl->gl_demote_state = LM_ST_EXCLUSIVE; gl->gl_hash = hash; gl->gl_ops = glops; + snprintf(gl->gl_strname, GDLM_STRNAME_BYTES, "%8x%16llx", name.ln_type, (unsigned long long)number); + memset(&gl->gl_lksb, 0, sizeof(struct dlm_lksb)); + gl->gl_lksb.sb_lvbptr = gl->gl_lvb; gl->gl_stamp = jiffies; gl->gl_tchange = jiffies; gl->gl_object = NULL; @@ -753,10 +717,6 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number, } } - error = gfs2_lm_get_lock(sdp, &name, &gl->gl_lock); - if (error) - goto fail_aspace; - write_lock(gl_lock_addr(hash)); tmp = search_bucket(hash, sdp, &name); if (tmp) { @@ -772,9 +732,6 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number, return 0; -fail_aspace: - if (gl->gl_aspace) - gfs2_aspace_put(gl->gl_aspace); fail: kmem_cache_free(gfs2_glock_cachep, gl); return error; @@ -966,7 +923,7 @@ do_cancel: if (!(gh->gh_flags & LM_FLAG_PRIORITY)) { spin_unlock(&gl->gl_spin); if (sdp->sd_lockstruct.ls_ops->lm_cancel) - sdp->sd_lockstruct.ls_ops->lm_cancel(gl->gl_lock); + sdp->sd_lockstruct.ls_ops->lm_cancel(gl); spin_lock(&gl->gl_spin); } return; @@ -1240,70 +1197,13 @@ void gfs2_glock_dq_uninit_m(unsigned int num_gh, struct gfs2_holder *ghs) gfs2_glock_dq_uninit(&ghs[x]); } -static int gfs2_lm_hold_lvb(struct gfs2_sbd *sdp, void *lock, char **lvbp) +void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state) { - int error = -EIO; - if (!sdp->sd_lockstruct.ls_ops->lm_hold_lvb) - return 0; - if (likely(!test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) - error = sdp->sd_lockstruct.ls_ops->lm_hold_lvb(lock, lvbp); - return error; -} - -/** - * gfs2_lvb_hold - attach a LVB from a glock - * @gl: The glock in question - * - */ - -int gfs2_lvb_hold(struct gfs2_glock *gl) -{ - int error; - - if (!atomic_read(&gl->gl_lvb_count)) { - error = gfs2_lm_hold_lvb(gl->gl_sbd, gl->gl_lock, &gl->gl_lvb); - if (error) - return error; - gfs2_glock_hold(gl); - } - atomic_inc(&gl->gl_lvb_count); - - return 0; -} - -/** - * gfs2_lvb_unhold - detach a LVB from a glock - * @gl: The glock in question - * - */ - -void gfs2_lvb_unhold(struct gfs2_glock *gl) -{ - struct gfs2_sbd *sdp = gl->gl_sbd; - - gfs2_glock_hold(gl); - gfs2_assert(gl->gl_sbd, atomic_read(&gl->gl_lvb_count) > 0); - if (atomic_dec_and_test(&gl->gl_lvb_count)) { - if (sdp->sd_lockstruct.ls_ops->lm_unhold_lvb) - sdp->sd_lockstruct.ls_ops->lm_unhold_lvb(gl->gl_lock, gl->gl_lvb); - gl->gl_lvb = NULL; - gfs2_glock_put(gl); - } - gfs2_glock_put(gl); -} - -static void blocking_cb(struct gfs2_sbd *sdp, struct lm_lockname *name, - unsigned int state) -{ - struct gfs2_glock *gl; unsigned long delay = 0; unsigned long holdtime; unsigned long now = jiffies; - gl = gfs2_glock_find(sdp, name); - if (!gl) - return; - + gfs2_glock_hold(gl); holdtime = gl->gl_tchange + gl->gl_ops->go_min_hold_time; if (time_before(now, holdtime)) delay = holdtime - now; @@ -1317,74 +1217,37 @@ static void blocking_cb(struct gfs2_sbd *sdp, struct lm_lockname *name, gfs2_glock_put(gl); } -static void gfs2_jdesc_make_dirty(struct gfs2_sbd *sdp, unsigned int jid) -{ - struct gfs2_jdesc *jd; - - spin_lock(&sdp->sd_jindex_spin); - list_for_each_entry(jd, &sdp->sd_jindex_list, jd_list) { - if (jd->jd_jid != jid) - continue; - jd->jd_dirty = 1; - break; - } - spin_unlock(&sdp->sd_jindex_spin); -} - /** - * gfs2_glock_cb - Callback used by locking module - * @sdp: Pointer to the superblock - * @type: Type of callback - * @data: Type dependent data pointer + * gfs2_glock_complete - Callback used by locking + * @gl: Pointer to the glock + * @ret: The return value from the dlm * - * Called by the locking module when it wants to tell us something. - * Either we need to drop a lock, one of our ASYNC requests completed, or - * a journal from another client needs to be recovered. */ -void gfs2_glock_cb(void *cb_data, unsigned int type, void *data) +void gfs2_glock_complete(struct gfs2_glock *gl, int ret) { - struct gfs2_sbd *sdp = cb_data; - - switch (type) { - case LM_CB_NEED_E: - blocking_cb(sdp, data, LM_ST_UNLOCKED); - return; - - case LM_CB_NEED_D: - blocking_cb(sdp, data, LM_ST_DEFERRED); - return; - - case LM_CB_NEED_S: - blocking_cb(sdp, data, LM_ST_SHARED); - return; - - case LM_CB_ASYNC: { - struct lm_async_cb *async = data; - struct gfs2_glock *gl; - - down_read(&gfs2_umount_flush_sem); - gl = gfs2_glock_find(sdp, &async->lc_name); - if (gfs2_assert_warn(sdp, gl)) + struct lm_lockstruct *ls = &gl->gl_sbd->sd_lockstruct; + down_read(&gfs2_umount_flush_sem); + gl->gl_reply = ret; + if (unlikely(test_bit(DFL_BLOCK_LOCKS, &ls->ls_flags))) { + struct gfs2_holder *gh; + spin_lock(&gl->gl_spin); + gh = find_first_waiter(gl); + if ((!(gh && (gh->gh_flags & LM_FLAG_NOEXP)) && + (gl->gl_target != LM_ST_UNLOCKED)) || + ((ret & ~LM_OUT_ST_MASK) != 0)) + set_bit(GLF_FROZEN, &gl->gl_flags); + spin_unlock(&gl->gl_spin); + if (test_bit(GLF_FROZEN, &gl->gl_flags)) { + up_read(&gfs2_umount_flush_sem); return; - gl->gl_reply = async->lc_ret; - set_bit(GLF_REPLY_PENDING, &gl->gl_flags); - if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0) - gfs2_glock_put(gl); - up_read(&gfs2_umount_flush_sem); - return; - } - - case LM_CB_NEED_RECOVERY: - gfs2_jdesc_make_dirty(sdp, *(unsigned int *)data); - if (sdp->sd_recoverd_process) - wake_up_process(sdp->sd_recoverd_process); - return; - - default: - gfs2_assert_warn(sdp, 0); - return; + } } + set_bit(GLF_REPLY_PENDING, &gl->gl_flags); + gfs2_glock_hold(gl); + if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0) + gfs2_glock_put(gl); + up_read(&gfs2_umount_flush_sem); } /** @@ -1515,6 +1378,27 @@ out: return has_entries; } + +/** + * thaw_glock - thaw out a glock which has an unprocessed reply waiting + * @gl: The glock to thaw + * + * N.B. When we freeze a glock, we leave a ref to the glock outstanding, + * so this has to result in the ref count being dropped by one. + */ + +static void thaw_glock(struct gfs2_glock *gl) +{ + if (!test_and_clear_bit(GLF_FROZEN, &gl->gl_flags)) + return; + down_read(&gfs2_umount_flush_sem); + set_bit(GLF_REPLY_PENDING, &gl->gl_flags); + gfs2_glock_hold(gl); + if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0) + gfs2_glock_put(gl); + up_read(&gfs2_umount_flush_sem); +} + /** * clear_glock - look at a glock and see if we can free it from glock cache * @gl: the glock to look at @@ -1539,6 +1423,20 @@ static void clear_glock(struct gfs2_glock *gl) gfs2_glock_put(gl); } +/** + * gfs2_glock_thaw - Thaw any frozen glocks + * @sdp: The super block + * + */ + +void gfs2_glock_thaw(struct gfs2_sbd *sdp) +{ + unsigned x; + + for (x = 0; x < GFS2_GL_HASH_SIZE; x++) + examine_bucket(thaw_glock, sdp, x); +} + /** * gfs2_gl_hash_clear - Empty out the glock hash table * @sdp: the filesystem @@ -1619,7 +1517,7 @@ static const char *hflags2str(char *buf, unsigned flags, unsigned long iflags) if (flags & LM_FLAG_NOEXP) *p++ = 'e'; if (flags & LM_FLAG_ANY) - *p++ = 'a'; + *p++ = 'A'; if (flags & LM_FLAG_PRIORITY) *p++ = 'p'; if (flags & GL_ASYNC) @@ -1683,6 +1581,10 @@ static const char *gflags2str(char *buf, const unsigned long *gflags) *p++ = 'i'; if (test_bit(GLF_REPLY_PENDING, gflags)) *p++ = 'r'; + if (test_bit(GLF_INITIAL, gflags)) + *p++ = 'i'; + if (test_bit(GLF_FROZEN, gflags)) + *p++ = 'F'; *p = 0; return buf; } @@ -1717,14 +1619,13 @@ static int __dump_glock(struct seq_file *seq, const struct gfs2_glock *gl) dtime *= 1000000/HZ; /* demote time in uSec */ if (!test_bit(GLF_DEMOTE, &gl->gl_flags)) dtime = 0; - gfs2_print_dbg(seq, "G: s:%s n:%u/%llu f:%s t:%s d:%s/%llu l:%d a:%d r:%d\n", + gfs2_print_dbg(seq, "G: s:%s n:%u/%llu f:%s t:%s d:%s/%llu a:%d r:%d\n", state2str(gl->gl_state), gl->gl_name.ln_type, (unsigned long long)gl->gl_name.ln_number, gflags2str(gflags_buf, &gl->gl_flags), state2str(gl->gl_target), state2str(gl->gl_demote_state), dtime, - atomic_read(&gl->gl_lvb_count), atomic_read(&gl->gl_ail_count), atomic_read(&gl->gl_ref)); -- cgit v1.2.2 From ac2425e7d319dec0523e52ee120a158ce6668cbd Mon Sep 17 00:00:00 2001 From: Steven Whitehouse Date: Tue, 13 Jan 2009 09:53:43 +0000 Subject: GFS2: Remove unused field from glock The time stamp field is unused in the glock now that we are using a shrinker, so that we can remove it and save sizeof(unsigned long) bytes in each glock. Signed-off-by: Steven Whitehouse --- fs/gfs2/glock.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'fs/gfs2/glock.c') diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index cd200a564c79..173e59ce9ad3 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -700,7 +700,6 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number, snprintf(gl->gl_strname, GDLM_STRNAME_BYTES, "%8x%16llx", name.ln_type, (unsigned long long)number); memset(&gl->gl_lksb, 0, sizeof(struct dlm_lksb)); gl->gl_lksb.sb_lvbptr = gl->gl_lvb; - gl->gl_stamp = jiffies; gl->gl_tchange = jiffies; gl->gl_object = NULL; gl->gl_sbd = sdp; @@ -1008,7 +1007,6 @@ void gfs2_glock_dq(struct gfs2_holder *gh) spin_lock(&gl->gl_spin); clear_bit(GLF_LOCK, &gl->gl_flags); } - gl->gl_stamp = jiffies; if (list_empty(&gl->gl_holders) && !test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) && !test_bit(GLF_DEMOTE, &gl->gl_flags)) -- cgit v1.2.2 From d8348de06f704fc34d24ec068546ecb1045fc11a Mon Sep 17 00:00:00 2001 From: Steven Whitehouse Date: Thu, 5 Feb 2009 10:12:38 +0000 Subject: GFS2: Fix deadlock on journal flush This patch fixes a deadlock when the journal is flushed and there are dirty inodes other than the one which caused the journal flush. Originally the journal flushing code was trying to obtain the transaction glock while running the flush code for an inode glock. We no longer require the transaction glock at this point in time since we know that any attempt to get the transaction glock from another node will result in a journal flush. So if we are flushing the journal, we can be sure that the transaction lock is still cached from when the transaction was started. By inlining a version of gfs2_trans_begin() (minus the bit which gets the transaction glock) we can avoid the deadlock problems caused if there is a demote request queued up on the transaction glock. In addition I've also moved the umount rwsem so that it covers the glock workqueue, since it all demotions are done by this workqueue now. That fixes a bug on umount which I came across while fixing the original problem. Reported-by: David Teigland Signed-off-by: Steven Whitehouse --- fs/gfs2/glock.c | 26 ++++++++++++-------------- 1 file changed, 12 insertions(+), 14 deletions(-) (limited to 'fs/gfs2/glock.c') diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index 173e59ce9ad3..ad8e121427c0 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -167,6 +167,7 @@ static void glock_free(struct gfs2_glock *gl) static void gfs2_glock_hold(struct gfs2_glock *gl) { + GLOCK_BUG_ON(gl, atomic_read(&gl->gl_ref) == 0); atomic_inc(&gl->gl_ref); } @@ -206,16 +207,15 @@ int gfs2_glock_put(struct gfs2_glock *gl) atomic_dec(&lru_count); } spin_unlock(&lru_lock); - GLOCK_BUG_ON(gl, !list_empty(&gl->gl_lru)); GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders)); glock_free(gl); rv = 1; goto out; } - write_unlock(gl_lock_addr(gl->gl_hash)); /* 1 for being hashed, 1 for having state != LM_ST_UNLOCKED */ if (atomic_read(&gl->gl_ref) == 2) gfs2_glock_schedule_for_reclaim(gl); + write_unlock(gl_lock_addr(gl->gl_hash)); out: return rv; } @@ -597,10 +597,11 @@ __acquires(&gl->gl_spin) GLOCK_BUG_ON(gl, test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags)); + down_read(&gfs2_umount_flush_sem); if (test_bit(GLF_DEMOTE, &gl->gl_flags) && gl->gl_demote_state != gl->gl_state) { if (find_first_holder(gl)) - goto out; + goto out_unlock; if (nonblock) goto out_sched; set_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags); @@ -611,23 +612,26 @@ __acquires(&gl->gl_spin) gfs2_demote_wake(gl); ret = do_promote(gl); if (ret == 0) - goto out; + goto out_unlock; if (ret == 2) - return; + goto out_sem; gh = find_first_waiter(gl); gl->gl_target = gh->gh_state; if (!(gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))) do_error(gl, 0); /* Fail queued try locks */ } do_xmote(gl, gh, gl->gl_target); +out_sem: + up_read(&gfs2_umount_flush_sem); return; out_sched: gfs2_glock_hold(gl); if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0) gfs2_glock_put(gl); -out: +out_unlock: clear_bit(GLF_LOCK, &gl->gl_flags); + goto out_sem; } static void glock_work_func(struct work_struct *work) @@ -1225,7 +1229,6 @@ void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state) void gfs2_glock_complete(struct gfs2_glock *gl, int ret) { struct lm_lockstruct *ls = &gl->gl_sbd->sd_lockstruct; - down_read(&gfs2_umount_flush_sem); gl->gl_reply = ret; if (unlikely(test_bit(DFL_BLOCK_LOCKS, &ls->ls_flags))) { struct gfs2_holder *gh; @@ -1236,16 +1239,13 @@ void gfs2_glock_complete(struct gfs2_glock *gl, int ret) ((ret & ~LM_OUT_ST_MASK) != 0)) set_bit(GLF_FROZEN, &gl->gl_flags); spin_unlock(&gl->gl_spin); - if (test_bit(GLF_FROZEN, &gl->gl_flags)) { - up_read(&gfs2_umount_flush_sem); + if (test_bit(GLF_FROZEN, &gl->gl_flags)) return; - } } set_bit(GLF_REPLY_PENDING, &gl->gl_flags); gfs2_glock_hold(gl); if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0) gfs2_glock_put(gl); - up_read(&gfs2_umount_flush_sem); } /** @@ -1389,12 +1389,10 @@ static void thaw_glock(struct gfs2_glock *gl) { if (!test_and_clear_bit(GLF_FROZEN, &gl->gl_flags)) return; - down_read(&gfs2_umount_flush_sem); set_bit(GLF_REPLY_PENDING, &gl->gl_flags); gfs2_glock_hold(gl); if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0) gfs2_glock_put(gl); - up_read(&gfs2_umount_flush_sem); } /** @@ -1580,7 +1578,7 @@ static const char *gflags2str(char *buf, const unsigned long *gflags) if (test_bit(GLF_REPLY_PENDING, gflags)) *p++ = 'r'; if (test_bit(GLF_INITIAL, gflags)) - *p++ = 'i'; + *p++ = 'I'; if (test_bit(GLF_FROZEN, gflags)) *p++ = 'F'; *p = 0; -- cgit v1.2.2 From 64d576ba23bfd9b770cbb0279200f479272eb859 Mon Sep 17 00:00:00 2001 From: Steven Whitehouse Date: Thu, 12 Feb 2009 13:31:58 +0000 Subject: GFS2: Add a "demote a glock" interface to sysfs This adds a sysfs file called demote_rq to GFS2's per filesystem directory. Its possible to use this file to demote arbitrary glocks in exactly the same way as if a request had come in from a remote node. This is intended for testing issues relating to caching of data under glocks. Despite that, the interface is generic enough to send requests to any type of glock, but be careful as its not always safe to send an arbitrary message to an arbitrary glock. For that reason and to prevent DoS, this interface is restricted to root only. The messages look like this: : Example: echo -n "2:13324 EX" >/sys/fs/gfs2/unity:myfs/demote_rq Which means "please demote inode glock (type 2) number 13324 so that I can get an EX (exclusive) lock". The lock modes are those which would normally be sent by a remote node in its callback so if you want to unlock a glock, you use EX, to demote to shared, use SH or PR (depending on whether you like GFS2 or DLM lock modes better!). If the glock doesn't exist, you'll get -ENOENT returned. If the arguments don't make sense, you'll get -EINVAL returned. The plan is that this interface will be used in combination with the blktrace patch which I recently posted for comments although it is, of course, still useful in its own right. Signed-off-by: Steven Whitehouse --- fs/gfs2/glock.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'fs/gfs2/glock.c') diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index ad8e121427c0..3984e47d1d33 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -684,10 +684,11 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number, gl = search_bucket(hash, sdp, &name); read_unlock(gl_lock_addr(hash)); - if (gl || !create) { - *glp = gl; + *glp = gl; + if (gl) return 0; - } + if (!create) + return -ENOENT; gl = kmem_cache_alloc(gfs2_glock_cachep, GFP_KERNEL); if (!gl) -- cgit v1.2.2