svn commit: r348772 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Slawa Olhovchenkov]

On Fri, Jun 07, 2019 at 06:35:42AM +0000, Andriy Gapon wrote:

> Author: avg
> Date: Fri Jun  7 06:35:42 2019
> New Revision: 348772
> URL: https://svnweb.freebsd.org/changeset/base/348772
> 
> Log:
>   Restore ARC MFU/MRU pressure
>   
>   Before r305323 (MFV r302991: 6950 ARC should cache compressed data)
>   arc_read() code did this for access to a ghost buffer:
>    arc_adapt() (from arc_get_data_buf())
>    arc_access(hdr, hash_lock)
>   I.e., we first checked access to the MFU ghost/MRU ghost buffer and
>   adapt MFU/MRU sizes (in arc_adapt()) and next move buffer from the ghost
>   state to regular.
>   
>   After r305323 the sequence is different:
>    arc_access(hdr, hash_lock);
>    arc_hdr_alloc_pabd(hdr);
>   I.e., we first move the buffer from the ghost state in arc_access() and
>   then we check access to buffer in ghost state (in arc_hdr_alloc_pabd()
>   -> arc_get_data_abd() -> arc_get_data_impl() -> arc_adapt()).  This is
>   incorrect: arc_adapt() never see access to the ghost buffer because
>   arc_access() already migrated the buffer from the ghost state to
>   regular.
>   
>   So, the fix is to restore a call to arc_adapt() before arc_access() and
>   to suppress the call to arc_adapt() after arc_access().
>   
>   Submitted by:	Slawa Olhovchenkov <slw at zxy.spb.ru>
>   MFC after:	2 weeks
>   Sponsored by:	Integros [integros.com]
>   Differential Revision: https://reviews.freebsd.org/D19094

Include in 11.3-RELEASE planed?