/* this call, unlike osi_FlushText, is supposed to discard caches that may
contain invalid information if a file is written remotely, but that may
contain valid information that needs to be written back if the file is
being written locally. It doesn't subsume osi_FlushText, since the latter
function may be needed to flush caches that are invalidated by local writes.
avc->pvnLock is already held, avc->lock is guaranteed not to be held (by
us, of course).
*/
void
osi_FlushPages(struct vcache *avc, afs_ucred_t *credp)
{
afs_hyper_t origDV;
#if defined(AFS_CACHE_BYPASS)
/* The optimization to check DV under read lock below is identical a
* change in CITI cache bypass work. The problem CITI found in 1999
* was that this code and background daemon doing prefetching competed
* for the vcache entry shared lock. It's not clear to me from the
* tech report, but it looks like CITI fixed the general prefetch code
* path as a bonus when experimenting on prefetch for cache bypass, see
* citi-tr-01-3.
*/
#endif
if (vType(avc) == VDIR) {
/* not applicable to directories; they're never mapped or stored in
* pages */
return;
}
ObtainReadLock(&avc->lock);
/* If we've already purged this version, or if we're the ones
* writing this version, don't flush it (could lose the
* data we're writing). */
if ((hcmp((avc->f.m.DataVersion), (avc->mapDV)) <= 0)
|| ((avc->execsOrWriters > 0) && afs_DirtyPages(avc))) {
ReleaseReadLock(&avc->lock);
return;
}
ReleaseReadLock(&avc->lock);
ObtainWriteLock(&avc->lock, 10);
/* Check again */
if ((hcmp((avc->f.m.DataVersion), (avc->mapDV)) <= 0)
|| ((avc->execsOrWriters > 0) && afs_DirtyPages(avc))) {
ReleaseWriteLock(&avc->lock);
return;
}
/* At this point, you might think that we can skip trying to flush pages
* if mapDV is zero, since a file with a zero DV will not have any data in
* it. However, some platforms (notably Linux 2.6.22+) will keep a page
* full of zeroes around for an empty file. So play it safe and always
* flush pages. */
AFS_STATCNT(osi_FlushPages);
hset(origDV, avc->f.m.DataVersion);
afs_Trace3(afs_iclSetp, CM_TRACE_FLUSHPAGES, ICL_TYPE_POINTER, avc,
ICL_TYPE_INT32, origDV.low, ICL_TYPE_INT32, avc->f.m.Length);
ReleaseWriteLock(&avc->lock);
#ifndef AFS_FBSD70_ENV
AFS_GUNLOCK();
#endif
osi_VM_FlushPages(avc, credp);
#ifndef AFS_FBSD70_ENV
AFS_GLOCK();
#endif
ObtainWriteLock(&avc->lock, 88);
/* do this last, and to original version, since stores may occur
* while executing above PUTPAGE call */
hset(avc->mapDV, origDV);
ReleaseWriteLock(&avc->lock);
}
/* this call, unlike osi_FlushText, is supposed to discard caches that may
contain invalid information if a file is written remotely, but that may
contain valid information that needs to be written back if the file is
being written locally. It doesn't subsume osi_FlushText, since the latter
function may be needed to flush caches that are invalidated by local writes.
avc->pvnLock is already held, avc->lock is guaranteed not to be held (by
us, of course).
*/
void
osi_FlushPages(struct vcache *avc, afs_ucred_t *credp)
{
#ifdef AFS_FBSD70_ENV
int vfslocked;
#endif
afs_hyper_t origDV;
#if defined(AFS_CACHE_BYPASS)
/* The optimization to check DV under read lock below is identical a
* change in CITI cache bypass work. The problem CITI found in 1999
* was that this code and background daemon doing prefetching competed
* for the vcache entry shared lock. It's not clear to me from the
* tech report, but it looks like CITI fixed the general prefetch code
* path as a bonus when experimenting on prefetch for cache bypass, see
* citi-tr-01-3.
*/
#endif
ObtainReadLock(&avc->lock);
/* If we've already purged this version, or if we're the ones
* writing this version, don't flush it (could lose the
* data we're writing). */
if ((hcmp((avc->f.m.DataVersion), (avc->mapDV)) <= 0)
|| ((avc->execsOrWriters > 0) && afs_DirtyPages(avc))) {
ReleaseReadLock(&avc->lock);
return;
}
ReleaseReadLock(&avc->lock);
ObtainWriteLock(&avc->lock, 10);
/* Check again */
if ((hcmp((avc->f.m.DataVersion), (avc->mapDV)) <= 0)
|| ((avc->execsOrWriters > 0) && afs_DirtyPages(avc))) {
ReleaseWriteLock(&avc->lock);
return;
}
if (hiszero(avc->mapDV)) {
hset(avc->mapDV, avc->f.m.DataVersion);
ReleaseWriteLock(&avc->lock);
return;
}
AFS_STATCNT(osi_FlushPages);
hset(origDV, avc->f.m.DataVersion);
afs_Trace3(afs_iclSetp, CM_TRACE_FLUSHPAGES, ICL_TYPE_POINTER, avc,
ICL_TYPE_INT32, origDV.low, ICL_TYPE_INT32, avc->f.m.Length);
ReleaseWriteLock(&avc->lock);
#ifdef AFS_FBSD70_ENV
vfslocked = VFS_LOCK_GIANT(AFSTOV(avc)->v_mount);
#endif
#ifndef AFS_FBSD70_ENV
AFS_GUNLOCK();
#endif
osi_VM_FlushPages(avc, credp);
#ifndef AFS_FBSD70_ENV
AFS_GLOCK();
#endif
#ifdef AFS_FBSD70_ENV
VFS_UNLOCK_GIANT(vfslocked);
#endif
ObtainWriteLock(&avc->lock, 88);
/* do this last, and to original version, since stores may occur
* while executing above PUTPAGE call */
hset(avc->mapDV, origDV);
ReleaseWriteLock(&avc->lock);
}
