d8b12a2162
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@zxy.spb.ru> MFC after: 2 weeks Sponsored by: Integros [integros.com] Differential Revision: https://reviews.freebsd.org/D19094 |
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