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This patch reestablishes the spec_fsync() guarentee that synchronous

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fsyncs, which typically occur during unmounting, will drain all dirty
buffers even if it takes multiple passes to do so.  The guarentee was
mangled by the last patch which solved a problem due to -current disabling
interrupts while holding giant (which caused an infinite spin loop waiting for
I/O to complete).  -stable does not have either patch, but has a similar
bug in the original spec_fsync() code which is triggered by a bug in the
softupdates umount code, a fix for which will be committed to -current
as soon as Kirk stamps it.  Then both solutions will be MFC'd to -stable.

-stable currently suffers from a combination of the softupdates bug and
a small window of opportunity in the original spec_fsync() code, and -stable
also suffers from the spin-loop bug but since interrupts are enabled the
spin resolves itself in a few milliseconds.
This commit is contained in:
Matthew Dillon 2001-01-29 08:19:28 +00:00
parent 52a90b77f9
commit 2a9737202a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=71777
2 changed files with 32 additions and 14 deletions
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23
sys/fs/specfs/spec_vnops.c
View File

@ -347,10 +347,12 @@ spec_fsync(ap)
struct buf *bp;
struct buf *nbp;
int s;
int maxretry = 10000; /* large, arbitrarily chosen */
if (!vn_isdisk(vp, NULL))
return (0);
loop1:
/*
* MARK/SCAN initialization to avoid infinite loops
*/
@ -364,7 +366,7 @@ spec_fsync(ap)
/*
* Flush all dirty buffers associated with a block device.
*/
loop:
loop2:
s = splbio();
for (bp = TAILQ_FIRST(&vp->v_dirtyblkhd); bp; bp = nbp) {
nbp = TAILQ_NEXT(bp, b_vnbufs);
@ -384,20 +386,27 @@ spec_fsync(ap)
splx(s);
bawrite(bp);
}
goto loop;
goto loop2;
}
/*
* If synchronous the caller expects us to completely resolve all
* dirty buffers in the system. Wait for in-progress I/O to
* complete (which could include background bitmap writes), then
* retry if dirty blocks still exist.
*/
if (ap->a_waitfor == MNT_WAIT) {
while (vp->v_numoutput) {
vp->v_flag |= VBWAIT;
(void) tsleep((caddr_t)&vp->v_numoutput, PRIBIO + 1, "spfsyn", 0);
}
#ifdef DIAGNOSTIC
if (!TAILQ_EMPTY(&vp->v_dirtyblkhd)) {
vprint("spec_fsync: dirty", vp);
splx(s);
goto loop;
if (--maxretry != 0) {
splx(s);
goto loop1;
}
vprint("spec_fsync: giving up on dirty", vp);
}
#endif
}
splx(s);
return (0);

23
sys/miscfs/specfs/spec_vnops.c
View File

@ -347,10 +347,12 @@ spec_fsync(ap)
struct buf *bp;
struct buf *nbp;
int s;
int maxretry = 10000; /* large, arbitrarily chosen */
if (!vn_isdisk(vp, NULL))
return (0);
loop1:
/*
* MARK/SCAN initialization to avoid infinite loops
*/
@ -364,7 +366,7 @@ spec_fsync(ap)
/*
* Flush all dirty buffers associated with a block device.
*/
loop:
loop2:
s = splbio();
for (bp = TAILQ_FIRST(&vp->v_dirtyblkhd); bp; bp = nbp) {
nbp = TAILQ_NEXT(bp, b_vnbufs);
@ -384,20 +386,27 @@ spec_fsync(ap)
splx(s);
bawrite(bp);
}
goto loop;
goto loop2;
}
/*
* If synchronous the caller expects us to completely resolve all
* dirty buffers in the system. Wait for in-progress I/O to
* complete (which could include background bitmap writes), then
* retry if dirty blocks still exist.
*/
if (ap->a_waitfor == MNT_WAIT) {
while (vp->v_numoutput) {
vp->v_flag |= VBWAIT;
(void) tsleep((caddr_t)&vp->v_numoutput, PRIBIO + 1, "spfsyn", 0);
}
#ifdef DIAGNOSTIC
if (!TAILQ_EMPTY(&vp->v_dirtyblkhd)) {
vprint("spec_fsync: dirty", vp);
splx(s);
goto loop;
if (--maxretry != 0) {
splx(s);
goto loop1;
}
vprint("spec_fsync: giving up on dirty", vp);
}
#endif
}
splx(s);
return (0);