diff options
| -rw-r--r-- | ufs/pager.c | 71 |
1 files changed, 62 insertions, 9 deletions
diff --git a/ufs/pager.c b/ufs/pager.c index d4bc87c5..0da2609e 100644 --- a/ufs/pager.c +++ b/ufs/pager.c @@ -22,6 +22,8 @@ spin_lock_t node2pagelock = SPIN_LOCK_INITIALIZER; +spin_lock_t unlocked_pagein_lock = SPIN_LOCK_INITIALIZER; + #ifdef DONT_CACHE_MEMORY_OBJECTS #define MAY_CACHE 0 #else @@ -34,15 +36,18 @@ struct port_bucket *pager_bucket; disk address (in disk block) in *ADDR. If *NPLOCK is set on return, then release that mutex after I/O on the data has completed. Set DISKSIZE to be the amount of valid data on disk. - (If this is an unallocated block, then set *ADDR to zero.) */ + (If this is an unallocated block, then set *ADDR to zero.) + ISREAD is non-zero iff this is for a pagein. */ static error_t find_address (struct user_pager_info *upi, vm_address_t offset, daddr_t *addr, int *disksize, - struct rwlock **nplock) + struct rwlock **nplock, + int isread) { error_t err; + struct rwlock *lock; assert (upi->type == DISK || upi->type == FILE_DATA); @@ -60,12 +65,58 @@ find_address (struct user_pager_info *upi, np = upi->np; - rwlock_reader_lock (&np->dn->allocptrlock); - *nplock = &np->dn->allocptrlock; + if (isread) + { + try_again: + + /* If we should allow an unlocked pagein, do so. (This + still has a slight race; there could be a pageout in progress + which is blocked on NP->np->allocptrlock itself. In that + case the pagein that should proceed unimpeded is blocked + in the pager library waiting for the pageout to complete. + I think this is sufficiently rare to put it off for the time + being.) */ + + spin_lock (&unlocked_pagein_lock); + if (offset >= upi->allow_unlocked_pagein + && (offset + vm_page_size + <= upi->allow_unlocked_pagein + upi->unlocked_pagein_length)) + { + spin_unlock (&unlocked_pagein_lock); + *nplock = 0; + goto have_lock; + } + spin_unlock (&unlocked_pagein_lock); + + /* Block on the rwlock if necessary; but when we wake up, + don't acquire it; check again from the top. + This is mutated inline from rwlock.h. */ + lock = &np->dn->allocptrlock; + mutex_lock (&lock->master); + if (lock->readers == -1 || lock->writers_waiting) + { + lock->readers_waiting++; + condition_wait (&lock->wakeup, &lock->master); + lock->readers_waiting--; + mutex_unlock (&lock->master); + goto try_again; + } + lock->readers++; + mutex_unlock (&lock->master); + *nplock = lock; + } + else + { + rwlock_reader_lock (&np->dn->allocptrlock); + *nplock = &np->dn->allocptrlock; + } + have_lock: + if (offset >= np->allocsize) { - rwlock_reader_unlock (&np->dn->allocptrlock); + if (*nplock) + rwlock_reader_unlock (*nplock); return EIO; } @@ -75,8 +126,8 @@ find_address (struct user_pager_info *upi, *disksize = __vm_page_size; err = fetch_indir_spec (np, lblkno (sblock, offset), indirs); - if (err) - rwlock_reader_unlock (&np->dn->allocptrlock); + if (err && *nplock) + rwlock_reader_unlock (*nplock); else { if (indirs[0].bno) @@ -104,7 +155,7 @@ pager_read_page (struct user_pager_info *pager, daddr_t addr; int disksize; - err = find_address (pager, page, &addr, &disksize, &nplock); + err = find_address (pager, page, &addr, &disksize, &nplock, 1); if (err) return err; @@ -143,7 +194,7 @@ pager_write_page (struct user_pager_info *pager, struct rwlock *nplock; error_t err; - err = find_address (pager, page, &addr, &disksize, &nplock); + err = find_address (pager, page, &addr, &disksize, &nplock, 0); if (err) return err; @@ -490,6 +541,8 @@ diskfs_get_filemap (struct node *np, vm_prot_t prot) upi->type = FILE_DATA; upi->np = np; upi->max_prot = prot; + upi->allow_unlocked_pagein = 0; + upi->unlocked_pagein_length = 0; diskfs_nref_light (np); upi->p = pager_create (upi, pager_bucket, MAY_CACHE, MEMORY_OBJECT_COPY_DELAY); |