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- Avoid a race in swaponsomething(): Calculate the new swdevt's first and

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end swblk and insert this new swdevt into the list of swap devices
   in the same critical section.
This commit is contained in:
Alan Cox 2003-10-29 05:42:28 +00:00
parent 9c855a36c1
commit 2d9974c1e8
1 changed files with 14 additions and 17 deletions
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31
sys/vm/swap_pager.c
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@ -2118,24 +2118,10 @@ done2:
static void
swaponsomething(struct vnode *vp, void *id, u_long nblks, sw_strategy_t *strategy, sw_close_t *close, udev_t udev)
{
struct swdevt *sp;
struct swdevt *sp, *tsp;
swblk_t dvbase;
u_long mblocks;
dvbase = 0;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
if (sp->sw_end >= dvbase) {
/*
* We put one uncovered page between the devices
* in order to definitively prevent any cross-device
* I/O requests
*/
dvbase = sp->sw_end + 1;
}
}
mtx_unlock(&sw_dev_mtx);
/*
* If we go beyond this, we get overflows in the radix
* tree bitmap code.
@ -2162,8 +2148,6 @@ swaponsomething(struct vnode *vp, void *id, u_long nblks, sw_strategy_t *strateg
sp->sw_flags = 0;
sp->sw_nblks = nblks;
sp->sw_used = 0;
sp->sw_first = dvbase;
sp->sw_end = dvbase + nblks;
sp->sw_strategy = strategy;
sp->sw_close = close;
@ -2174,7 +2158,20 @@ swaponsomething(struct vnode *vp, void *id, u_long nblks, sw_strategy_t *strateg
*/
blist_free(sp->sw_blist, 2, nblks - 2);
dvbase = 0;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(tsp, &swtailq, sw_list) {
if (tsp->sw_end >= dvbase) {
/*
* We put one uncovered page between the devices
* in order to definitively prevent any cross-device
* I/O requests
*/
dvbase = tsp->sw_end + 1;
}
}
sp->sw_first = dvbase;
sp->sw_end = dvbase + nblks;
TAILQ_INSERT_TAIL(&swtailq, sp, sw_list);
mtx_unlock(&sw_dev_mtx);
nswapdev++;