Author: imp Date: Tue Sep 8 17:47:56 2015 New Revision: 287567 URL: https://svnweb.freebsd.org/changeset/base/287567
Log: The swap pager is compatible with direct dispatch. It does its own locking and doesn't sleep. Flag the consumer we create as such. In addition, decrement the in flight index when we have an out of memory error after having incremented it previously. This would have prevented swapoff from working if the swap pager ever hit a resource shortage trying to swap out something (the swap in path always waits for a bio, so won't have this issue). Simplify the close logic by abandoning the use of private and initializing the index to 1 and dropping that reference when we previously set private. Also, set sw_id only while sw_dev_mtx is held. This should only affect swapping to a vnode, as opposed to a geom whose close always sets it to NULL with sw_dev_mtx held. Differential Review: https://reviews.freebsd.org/D3547 Modified: head/sys/vm/swap_pager.c Modified: head/sys/vm/swap_pager.c ============================================================================== --- head/sys/vm/swap_pager.c Tue Sep 8 17:20:12 2015 (r287566) +++ head/sys/vm/swap_pager.c Tue Sep 8 17:47:56 2015 (r287567) @@ -2345,8 +2345,8 @@ swapoff_one(struct swdevt *sp, struct uc swap_pager_swapoff(sp); sp->sw_close(curthread, sp); - sp->sw_id = NULL; mtx_lock(&sw_dev_mtx); + sp->sw_id = NULL; TAILQ_REMOVE(&swtailq, sp, sw_list); nswapdev--; if (nswapdev == 0) { @@ -2532,6 +2532,33 @@ swapgeom_close_ev(void *arg, int flags) g_destroy_consumer(cp); } +/* + * Add a reference to the g_consumer for an inflight transaction. + */ +static void +swapgeom_acquire(struct g_consumer *cp) +{ + + mtx_assert(&sw_dev_mtx, MA_OWNED); + cp->index++; +} + +/* + * Remove a reference from the g_consumer. Post a close event if + * all referneces go away. + */ +static void +swapgeom_release(struct g_consumer *cp, struct swdevt *sp) +{ + + mtx_assert(&sw_dev_mtx, MA_OWNED); + cp->index--; + if (cp->index == 0) { + if (g_post_event(swapgeom_close_ev, cp, M_NOWAIT, NULL) == 0) + sp->sw_id = NULL; + } +} + static void swapgeom_done(struct bio *bp2) { @@ -2547,13 +2574,9 @@ swapgeom_done(struct bio *bp2) bp->b_resid = bp->b_bcount - bp2->bio_completed; bp->b_error = bp2->bio_error; bufdone(bp); + sp = bp2->bio_caller1; mtx_lock(&sw_dev_mtx); - if ((--cp->index) == 0 && cp->private) { - if (g_post_event(swapgeom_close_ev, cp, M_NOWAIT, NULL) == 0) { - sp = bp2->bio_caller1; - sp->sw_id = NULL; - } - } + swapgeom_release(cp, sp); mtx_unlock(&sw_dev_mtx); g_destroy_bio(bp2); } @@ -2573,13 +2596,16 @@ swapgeom_strategy(struct buf *bp, struct bufdone(bp); return; } - cp->index++; + swapgeom_acquire(cp); mtx_unlock(&sw_dev_mtx); if (bp->b_iocmd == BIO_WRITE) bio = g_new_bio(); else bio = g_alloc_bio(); if (bio == NULL) { + mtx_lock(&sw_dev_mtx); + swapgeom_release(cp, sp); + mtx_unlock(&sw_dev_mtx); bp->b_error = ENOMEM; bp->b_ioflags |= BIO_ERROR; bufdone(bp); @@ -2619,7 +2645,12 @@ swapgeom_orphan(struct g_consumer *cp) break; } } - cp->private = (void *)(uintptr_t)1; + /* + * Drop reference we were created with. Do directly since we're in a + * special context where we don't have to queue the call to + * swapgeom_close_ev(). + */ + cp->index--; destroy = ((sp != NULL) && (cp->index == 0)); if (destroy) sp->sw_id = NULL; @@ -2680,8 +2711,8 @@ swapongeom_ev(void *arg, int flags) if (gp == NULL) gp = g_new_geomf(&g_swap_class, "swap"); cp = g_new_consumer(gp); - cp->index = 0; /* Number of active I/Os. */ - cp->private = NULL; /* Orphanization flag */ + cp->index = 1; /* Number of active I/Os, plus one for being active. */ + cp->flags |= G_CF_DIRECT_SEND | G_CF_DIRECT_RECEIVE; g_attach(cp, pp); /* * XXX: Everytime you think you can improve the margin for _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
