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replace a comment about zfs recv -F corner case with a longer, more detailed one

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The old comment in zfs_rezget explains what situation the code handles,
the new comment also describes how the situation can arise.

Also, re-join a line that became sufficiently shorti some time ago.

Differential Revision:	https://reviews.freebsd.org/D2352
Reviewed by:	delphij, smh
MFC after:	12 days
This commit is contained in:
Andriy Gapon 2015-04-28 09:19:40 +00:00
parent 1af760ce1b
commit 9bc3222765
1 changed files with 17 additions and 7 deletions
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24
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_znode.c
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@ -1320,15 +1320,25 @@ zfs_rezget(znode_t *zp)
}
/*
* XXXPJD: Not sure how is that possible, but under heavy
* zfs recv -F load it happens that z_gen is the same, but
* vnode type is different than znode type. This would mean
* that for example regular file was replaced with directory
* which has the same object number.
* It is highly improbable but still quite possible that two
* objects in different datasets are created with the same
* object numbers and in transaction groups with the same
* numbers. znodes corresponding to those objects would
* have the same z_id and z_gen, but their other attributes
* may be different.
* zfs recv -F may replace one of such objects with the other.
* As a result file properties recorded in the replaced
* object's vnode may no longer match the received object's
* properties. At present the only cached property is the
* files type recorded in v_type.
* So, handle this case by leaving the old vnode and znode
* disassociated from the actual object. A new vnode and a
* znode will be created if the object is accessed
* (e.g. via a look-up). The old vnode and znode will be
* recycled when the last vnode reference is dropped.
*/
vp = ZTOV(zp);
if (vp != NULL &&
vp->v_type != IFTOVT((mode_t)zp->z_mode)) {
if (vp != NULL && vp->v_type != IFTOVT((mode_t)zp->z_mode)) {
zfs_znode_dmu_fini(zp);
ZFS_OBJ_HOLD_EXIT(zfsvfs, obj_num);
return (EIO);