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gfs2: Add GL_NOBLOCK flag 

Add a GL_NOBLOCK flag for trying to take a glock without sleeping.  This
will be used for implementing non-blocking lookup (MAY_NOT_BLOCK in
gfs2_permission, LOOKUP_RCU in gfs2_drevalidate).

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Andreas Gruenbacher 2023-11-13 16:49:38 +01:00
parent 95d0f62525
commit f9f229c1f7
2 changed files with 39 additions and 1 deletions
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39
fs/gfs2/glock.c
View File

@ -516,6 +516,23 @@ static inline struct gfs2_holder *find_first_waiter(const struct gfs2_glock *gl)
return NULL;
}
/**
* find_last_waiter - find the last gh that's waiting for the glock
* @gl: the glock
*
* This also is a fast way of finding out if there are any waiters.
*/
static inline struct gfs2_holder *find_last_waiter(const struct gfs2_glock *gl)
{
struct gfs2_holder *gh;
if (list_empty(&gl->gl_holders))
return NULL;
gh = list_last_entry(&gl->gl_holders, struct gfs2_holder, gh_list);
return test_bit(HIF_HOLDER, &gh->gh_iflags) ? NULL : gh;
}
/**
* state_change - record that the glock is now in a different state
* @gl: the glock
@ -1555,11 +1572,30 @@ trap_recursive:
int gfs2_glock_nq(struct gfs2_holder *gh)
{
struct gfs2_glock *gl = gh->gh_gl;
int error = 0;
int error;
if (glock_blocked_by_withdraw(gl) && !(gh->gh_flags & LM_FLAG_NOEXP))
return -EIO;
if (gh->gh_flags & GL_NOBLOCK) {
struct gfs2_holder *current_gh;
error = -ECHILD;
spin_lock(&gl->gl_lockref.lock);
if (find_last_waiter(gl))
goto unlock;
current_gh = find_first_holder(gl);
if (!may_grant(gl, current_gh, gh))
goto unlock;
set_bit(HIF_HOLDER, &gh->gh_iflags);
list_add_tail(&gh->gh_list, &gl->gl_holders);
trace_gfs2_promote(gh);
error = 0;
unlock:
spin_unlock(&gl->gl_lockref.lock);
return error;
}
if (test_bit(GLF_LRU, &gl->gl_flags))
gfs2_glock_remove_from_lru(gl);
@ -1575,6 +1611,7 @@ int gfs2_glock_nq(struct gfs2_holder *gh)
run_queue(gl, 1);
spin_unlock(&gl->gl_lockref.lock);
error = 0;
if (!(gh->gh_flags & GL_ASYNC))
error = gfs2_glock_wait(gh);

1
fs/gfs2/glock.h
View File

@ -84,6 +84,7 @@ enum {
#define GL_SKIP 0x0100
#define GL_NOPID 0x0200
#define GL_NOCACHE 0x0400
#define GL_NOBLOCK 0x0800
/*
* lm_async_cb return flags