From 19a47cb1c2be6da9b9d4a395a7afc07da4813a5f Mon Sep 17 00:00:00 2001 From: Richard Yao Date: Fri, 5 Feb 2016 23:10:13 -0500 Subject: [PATCH] Call dmu_read_uio_dbuf() in zvol_read() The difference between `dmu_read_uio()` and `dmu_read_uio_dbuf()` is that the former takes a hold while the latter uses an existing hold. `zfs_read()` in the ZPL will use `dmu_read_uio_dbuf()` while our analogous `zvol_write()` will use `dmu_write_uio_dbuf()`, but for no apparent reason, we inherited a `zvol_read()` function from OpenSolaris that does `dmu_read_uio()`. illumos-gate also still uses `dmu_read_uio()` to this day. Lets switch to `dmu_read_uio_dbuf()`, which is more performant. Signed-off-by: Richard Yao Signed-off-by: Brian Behlendorf Signed-off-by: Tim Chase Signed-off-by: Chunwei Chen Closes #4316 --- module/zfs/zvol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c index 7269cf0c82..52774a82ce 100644 --- a/module/zfs/zvol.c +++ b/module/zfs/zvol.c @@ -731,7 +731,7 @@ zvol_read(zvol_state_t *zv, uio_t *uio) if (bytes > volsize - uio->uio_loffset) bytes = volsize - uio->uio_loffset; - error = dmu_read_uio(zv->zv_objset, ZVOL_OBJ, uio, bytes); + error = dmu_read_uio_dbuf(zv->zv_dbuf, uio, bytes); if (error) { /* convert checksum errors into IO errors */ if (error == ECKSUM)