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diff --git a/sys/geom/zero/g_zero.c b/sys/geom/zero/g_zero.c
--- a/sys/geom/zero/g_zero.c
+++ b/sys/geom/zero/g_zero.c
@@ -3,6 +3,7 @@
*
* Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
* All rights reserved.
+ * Copyright (c) 2025 Mateusz Piotrowski <0mp@FreeBSD.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
@@ -34,53 +35,97 @@
#include <sys/queue.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
+#include <sys/uio.h>
+#include <sys/types.h>
#include <geom/geom.h>
#define G_ZERO_CLASS_NAME "ZERO"
-static int g_zero_clear_sysctl(SYSCTL_HANDLER_ARGS);
+static int g_zero_byte_sysctl(SYSCTL_HANDLER_ARGS);
SYSCTL_DECL(_kern_geom);
static SYSCTL_NODE(_kern_geom, OID_AUTO, zero, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"GEOM_ZERO stuff");
static int g_zero_clear = 1;
-SYSCTL_PROC(_kern_geom_zero, OID_AUTO, clear,
- CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, &g_zero_clear, 0,
- g_zero_clear_sysctl, "I",
+SYSCTL_INT(_kern_geom_zero, OID_AUTO, clear,
+ CTLFLAG_RWTUN, &g_zero_clear, 0,
"Clear read data buffer");
static int g_zero_byte = 0;
-SYSCTL_INT(_kern_geom_zero, OID_AUTO, byte, CTLFLAG_RWTUN, &g_zero_byte, 0,
+static uint8_t g_zero_buffer[PAGE_SIZE];
+SYSCTL_PROC(_kern_geom_zero, OID_AUTO, byte,
+ CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, &g_zero_byte, 0,
+ g_zero_byte_sysctl, "I",
"Byte (octet) value to clear the buffers with");
static struct g_provider *gpp;
static int
-g_zero_clear_sysctl(SYSCTL_HANDLER_ARGS)
+g_zero_byte_sysctl(SYSCTL_HANDLER_ARGS)
{
int error;
- error = sysctl_handle_int(oidp, &g_zero_clear, 0, req);
+ // XXX: Confirm that this is called on module load as well.
+ // XXX: Shouldn't we lock here to avoid changing the byte value if the
+ // driver is in the process of handling I/O?
+ error = sysctl_handle_int(oidp, &g_zero_byte, 0, req);
if (error != 0 || req->newptr == NULL)
return (error);
- if (gpp == NULL)
- return (ENXIO);
- if (g_zero_clear)
- gpp->flags &= ~G_PF_ACCEPT_UNMAPPED;
- else
- gpp->flags |= G_PF_ACCEPT_UNMAPPED;
+ memset(g_zero_buffer, g_zero_byte, PAGE_SIZE);
return (0);
}
+static void
+g_zero_fill_pages(struct bio *bp)
+{
+ struct iovec aiovec;
+ struct uio auio;
+ size_t length;
+ vm_offset_t offset;
+
+ aiovec.iov_base = g_zero_buffer;
+ aiovec.iov_len = PAGE_SIZE;
+ auio.uio_iov = &aiovec;
+ auio.uio_iovcnt = 1;
+ auio.uio_offset = 0;
+ auio.uio_segflg = UIO_SYSSPACE;
+ auio.uio_rw = UIO_WRITE;
+ auio.uio_td = curthread;
+
+ /*
+ * To handle the unmapped I/O request, we need to fill the pages in the
+ * bp->bio_ma array with the g_zero_byte value. However, instead of
+ * setting every byte individually, we use uiomove_fromphys() to fill a
+ * page at a time with g_zero_buffer.
+ */
+ bp->bio_resid = bp->bio_length;
+ offset = bp->bio_ma_offset & PAGE_MASK;
+ for (int i = 0; i < bp->bio_ma_n && bp->bio_resid > 0; i++) {
+ length = MIN(PAGE_SIZE - offset, bp->bio_resid);
+ auio.uio_resid = length;
+
+ (void)uiomove_fromphys(&bp->bio_ma[i], offset, length, &auio);
+
+ offset = 0;
+ bp->bio_resid -= length;
+ }
+}
+
+
static void
g_zero_start(struct bio *bp)
{
- int error = ENXIO;
+ int error;
switch (bp->bio_cmd) {
case BIO_READ:
- if (g_zero_clear && (bp->bio_flags & BIO_UNMAPPED) == 0)
- memset(bp->bio_data, g_zero_byte, bp->bio_length);
+ if (g_zero_clear) {
+ if ((bp->bio_flags & BIO_UNMAPPED) != 0)
+ g_zero_fill_pages(bp);
+ else
+ memset(bp->bio_data, g_zero_byte,
+ bp->bio_length);
+ }
/* FALLTHROUGH */
case BIO_DELETE:
case BIO_WRITE:
@@ -106,9 +151,8 @@
gp->start = g_zero_start;
gp->access = g_std_access;
gpp = pp = g_new_providerf(gp, "%s", gp->name);
- pp->flags |= G_PF_DIRECT_SEND | G_PF_DIRECT_RECEIVE;
- if (!g_zero_clear)
- pp->flags |= G_PF_ACCEPT_UNMAPPED;
+ pp->flags |= G_PF_ACCEPT_UNMAPPED | G_PF_DIRECT_SEND |
+ G_PF_DIRECT_RECEIVE;
pp->mediasize = 1152921504606846976LLU;
pp->sectorsize = 512;
g_error_provider(pp, 0);

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