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gfs2: Allow node-wide exclusive glock sharing
Introduce a new LM_FLAG_NODE_SCOPE glock holder flag: when taking a glock in LM_ST_EXCLUSIVE (EX) mode and with the LM_FLAG_NODE_SCOPE flag set, the exclusive lock is shared among all local processes who are holding the glock in EX mode and have the LM_FLAG_NODE_SCOPE flag set. From the point of view of other nodes, the lock is still held exclusively. A future patch will start using this flag to improve performance with rgrp sharing. Signed-off-by: Bob Peterson <rpeterso@redhat.com> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
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@ -313,9 +313,23 @@ void gfs2_glock_put(struct gfs2_glock *gl)
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static inline int may_grant(const struct gfs2_glock *gl, const struct gfs2_holder *gh)
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{
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const struct gfs2_holder *gh_head = list_first_entry(&gl->gl_holders, const struct gfs2_holder, gh_list);
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if ((gh->gh_state == LM_ST_EXCLUSIVE ||
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gh_head->gh_state == LM_ST_EXCLUSIVE) && gh != gh_head)
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return 0;
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if (gh != gh_head) {
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/**
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* Here we make a special exception to grant holders who agree
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* to share the EX lock with other holders who also have the
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* bit set. If the original holder has the LM_FLAG_NODE_SCOPE bit
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* is set, we grant more holders with the bit set.
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*/
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if (gh_head->gh_state == LM_ST_EXCLUSIVE &&
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(gh_head->gh_flags & LM_FLAG_NODE_SCOPE) &&
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gh->gh_state == LM_ST_EXCLUSIVE &&
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(gh->gh_flags & LM_FLAG_NODE_SCOPE))
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return 1;
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if ((gh->gh_state == LM_ST_EXCLUSIVE ||
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gh_head->gh_state == LM_ST_EXCLUSIVE))
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return 0;
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}
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if (gl->gl_state == gh->gh_state)
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return 1;
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if (gh->gh_flags & GL_EXACT)
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@ -2030,6 +2044,8 @@ static const char *hflags2str(char *buf, u16 flags, unsigned long iflags)
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*p++ = 'A';
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if (flags & LM_FLAG_PRIORITY)
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*p++ = 'p';
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if (flags & LM_FLAG_NODE_SCOPE)
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*p++ = 'n';
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if (flags & GL_ASYNC)
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*p++ = 'a';
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if (flags & GL_EXACT)
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@ -75,6 +75,11 @@ enum {
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* request and directly join the other shared lock. A shared lock request
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* without the priority flag might be forced to wait until the deferred
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* requested had acquired and released the lock.
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*
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* LM_FLAG_NODE_SCOPE
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* This holder agrees to share the lock within this node. In other words,
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* the glock is held in EX mode according to DLM, but local holders on the
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* same node can share it.
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*/
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#define LM_FLAG_TRY 0x0001
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@ -82,6 +87,7 @@ enum {
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#define LM_FLAG_NOEXP 0x0004
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#define LM_FLAG_ANY 0x0008
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#define LM_FLAG_PRIORITY 0x0010
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#define LM_FLAG_NODE_SCOPE 0x0020
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#define GL_ASYNC 0x0040
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#define GL_EXACT 0x0080
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#define GL_SKIP 0x0100
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