Author: mjg
Date: Mon May 25 04:56:41 2020
New Revision: 361440
URL: https://svnweb.freebsd.org/changeset/base/361440
Log:
vfs: restore mtx-protected foffset locking for 32 bit platforms
They depend on it to accurately read the offset.
The new code is not used as it would add an interrupt enable/disable
trip on top of the atomic.
This also fixes a bug where 32-bit nolock request would still lock the offset.
No changes for 64-bit.
Reported by: emaste
Modified:
head/sys/kern/vfs_vnops.c
Modified: head/sys/kern/vfs_vnops.c
==============================================================================
--- head/sys/kern/vfs_vnops.c Mon May 25 04:17:01 2020 (r361439)
+++ head/sys/kern/vfs_vnops.c Mon May 25 04:56:41 2020 (r361440)
@@ -672,6 +672,7 @@ vn_rdwr_inchunks(enum uio_rw rw, struct vnode *vp, voi
return (error);
}
+#if OFF_MAX <= LONG_MAX
off_t
foffset_lock(struct file *fp, int flags)
{
@@ -681,14 +682,12 @@ foffset_lock(struct file *fp, int flags)
KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed"));
-#if OFF_MAX <= LONG_MAX
/*
* Caller only wants the current f_offset value. Assume that
* the long and shorter integer types reads are atomic.
*/
if ((flags & FOF_NOLOCK) != 0)
return (fp->f_offset);
-#endif
/*
* According to McKusick the vn lock was protecting f_offset here.
@@ -737,10 +736,8 @@ foffset_unlock(struct file *fp, off_t val, int flags)
if ((flags & FOF_NEXTOFF) != 0)
fp->f_nextoff = val;
-#if OFF_MAX <= LONG_MAX
if ((flags & FOF_NOLOCK) != 0)
return;
-#endif
flagsp = &fp->f_vnread_flags;
state = atomic_load_16(flagsp);
@@ -755,6 +752,53 @@ foffset_unlock(struct file *fp, off_t val, int flags)
sleepq_broadcast(&fp->f_vnread_flags, SLEEPQ_SLEEP, 0, 0);
sleepq_release(&fp->f_vnread_flags);
}
+#else
+off_t
+foffset_lock(struct file *fp, int flags)
+{
+ struct mtx *mtxp;
+ off_t res;
+
+ KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed"));
+
+ mtxp = mtx_pool_find(mtxpool_sleep, fp);
+ mtx_lock(mtxp);
+ if ((flags & FOF_NOLOCK) == 0) {
+ while (fp->f_vnread_flags & FOFFSET_LOCKED) {
+ fp->f_vnread_flags |= FOFFSET_LOCK_WAITING;
+ msleep(&fp->f_vnread_flags, mtxp, PUSER -1,
+ "vofflock", 0);
+ }
+ fp->f_vnread_flags |= FOFFSET_LOCKED;
+ }
+ res = fp->f_offset;
+ mtx_unlock(mtxp);
+ return (res);
+}
+
+void
+foffset_unlock(struct file *fp, off_t val, int flags)
+{
+ struct mtx *mtxp;
+
+ KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed"));
+
+ mtxp = mtx_pool_find(mtxpool_sleep, fp);
+ mtx_lock(mtxp);
+ if ((flags & FOF_NOUPDATE) == 0)
+ fp->f_offset = val;
+ if ((flags & FOF_NEXTOFF) != 0)
+ fp->f_nextoff = val;
+ if ((flags & FOF_NOLOCK) == 0) {
+ KASSERT((fp->f_vnread_flags & FOFFSET_LOCKED) != 0,
+ ("Lost FOFFSET_LOCKED"));
+ if (fp->f_vnread_flags & FOFFSET_LOCK_WAITING)
+ wakeup(&fp->f_vnread_flags);
+ fp->f_vnread_flags = 0;
+ }
+ mtx_unlock(mtxp);
+}
+#endif
void
foffset_lock_uio(struct file *fp, struct uio *uio, int flags)
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