diff options
| -rw-r--r-- | fs/gfs2/glock.c | 39 | ||||
| -rw-r--r-- | fs/gfs2/glock.h | 1 |
2 files changed, 39 insertions, 1 deletions
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index d6bf1f8c25dc..2cb65f76eec8 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -517,6 +517,23 @@ static inline struct gfs2_holder *find_first_waiter(const struct gfs2_glock *gl) } /** + * 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 * @new_state: the new state @@ -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); diff --git a/fs/gfs2/glock.h b/fs/gfs2/glock.h index 61197598abfd..0114f3e0ebe0 100644 --- a/fs/gfs2/glock.h +++ b/fs/gfs2/glock.h @@ -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 |