diff options
| -rw-r--r-- | sys/src/9/port/swap.c | 45 |
1 files changed, 23 insertions, 22 deletions
diff --git a/sys/src/9/port/swap.c b/sys/src/9/port/swap.c index b8e0631ff..c51417520 100644 --- a/sys/src/9/port/swap.c +++ b/sys/src/9/port/swap.c @@ -49,7 +49,7 @@ swapinit(void) swapimage.notext = 1; } -uintptr +static uintptr newswap(void) { uchar *look; @@ -64,7 +64,8 @@ newswap(void) if(look == 0) panic("inconsistent swap"); - *look = 1; + *look = 2; /* ref for pte + io transaction */ + swapalloc.last = look; swapalloc.free--; unlock(&swapalloc); @@ -324,12 +325,14 @@ pagepte(int type, Page **pg) case SG_STACK: case SG_SHARED: /* - * get a new swap address and clear any pages - * referring to it from the cache + * get a new swap address with swapcount 2, one for the pte + * and one extra ref for us while we write the page to disk */ daddr = newswap(); if(daddr == ~0) break; + + /* clear any pages referring to it from the cache */ cachedel(&swapimage, daddr); lock(outp); @@ -338,12 +341,6 @@ pagepte(int type, Page **pg) uncachepage(outp); /* - * incr the reference count to make sure it sticks around while - * being written - */ - outp->ref++; - - /* * enter it into the cache so that a fault happening * during the write will grab the page from the cache * rather than one partially written to the disk @@ -396,23 +393,27 @@ executeio(void) if(ioptr > conf.nswppo) panic("executeio: ioptr %d > %d", ioptr, conf.nswppo); out = iolist[i]; - k = kmap(out); - kaddr = (char*)VA(k); - if(waserror()) - panic("executeio: page out I/O error"); + /* only write when swap address still referenced */ + if(swapcount(out->daddr) > 1){ + k = kmap(out); + kaddr = (char*)VA(k); + + if(waserror()) + panic("executeio: page out I/O error"); - n = devtab[c->type]->write(c, kaddr, BY2PG, out->daddr); - if(n != BY2PG) - nexterror(); + n = devtab[c->type]->write(c, kaddr, BY2PG, out->daddr); + if(n != BY2PG) + nexterror(); + + kunmap(k); + poperror(); + } - kunmap(k); - poperror(); + /* drop our extra swap reference */ + putswap((Page*)out->daddr); /* Free up the page after I/O */ - lock(out); - out->ref--; - unlock(out); putpage(out); } ioptr = 0; |