diff options
Diffstat (limited to 'module')
| -rw-r--r-- | module/zfs/arc.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/module/zfs/arc.c b/module/zfs/arc.c index 8f6ca1a28..579e78bef 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -6032,6 +6032,23 @@ top: ARC_FLAG_PREDICTIVE_PREFETCH); } + /* + * If there are multiple threads reading the same block + * and that block is not yet in the ARC, then only one + * thread will do the physical I/O and all other + * threads will wait until that I/O completes. + * Synchronous reads use the b_cv whereas nowait reads + * register a callback. Both are signalled/called in + * arc_read_done. + * + * Errors of the physical I/O may need to be propagated + * to the pio. For synchronous reads, we simply restart + * this function and it will reassess. Nowait reads + * attach the acb_zio_dummy zio to pio and + * arc_read_done propagates the physical I/O's io_error + * to acb_zio_dummy, and thereby to pio. + */ + if (*arc_flags & ARC_FLAG_WAIT) { cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); mutex_exit(hash_lock); |