svn commit: r298900 - in head/sys/boot: common efi/libefi i386/libi386
Allan Jude
allanjude at FreeBSD.org
Sun May 1 21:07:01 UTC 2016
Author: allanjude
Date: Sun May 1 21:06:59 2016
New Revision: 298900
URL: https://svnweb.freebsd.org/changeset/base/298900
Log:
bcache read ahead may attempt to read past end of disk
The new bcache code does not know the size of the disk, and therefore may attempt to read past the end of the disk while trying to fill its read-ahead cache.
This is usually not an issue, it fails gracefully on all of my machines, but some BIOSes seem to retry the reads for up to 30 seconds each, resulting in a long stall during boot
Submitted by: Toomas Soome <tsoome at me.com>
Reviewed by: jhb, np
Differential Revision: https://reviews.freebsd.org/D6109
Modified:
head/sys/boot/common/bcache.c
head/sys/boot/efi/libefi/efipart.c
head/sys/boot/i386/libi386/bioscd.c
head/sys/boot/i386/libi386/biosdisk.c
Modified: head/sys/boot/common/bcache.c
==============================================================================
--- head/sys/boot/common/bcache.c Sun May 1 20:57:10 2016 (r298899)
+++ head/sys/boot/common/bcache.c Sun May 1 21:06:59 2016 (r298900)
@@ -272,20 +272,43 @@ read_strategy(void *devdata, int rw, dad
for (i = 0; i < p_size; i++) {
bcache_invalidate(bc, p_blk + i);
}
+
r_size = 0;
+ /*
+ * with read-ahead, it may happen we are attempting to read past
+ * disk end, as bcache has no information about disk size.
+ * in such case we should get partial read if some blocks can be
+ * read or error, if no blocks can be read.
+ * in either case we should return the data in bcache and only
+ * return error if there is no data.
+ */
result = dd->dv_strategy(dd->dv_devdata, rw, p_blk, 0,
p_size * bcache_blksize, p_buf, &r_size);
- if (result)
- goto done;
-
r_size /= bcache_blksize;
for (i = 0; i < r_size; i++)
bcache_insert(bc, p_blk + i);
- bcache_rablks += ra;
- bcopy(bc->bcache_data + (bcache_blksize * BHASH(bc, blk)) + offset, buf,
- size);
+ /* update ra statistics */
+ if (r_size != 0) {
+ if (r_size < p_size)
+ bcache_rablks += (p_size - r_size);
+ else
+ bcache_rablks += ra;
+ }
+
+ /* check how much data can we copy */
+ for (i = 0; i < nblk; i++) {
+ if (BCACHE_LOOKUP(bc, (daddr_t)(blk + i)))
+ break;
+ }
+
+ size = i * bcache_blksize;
+ if (size != 0) {
+ bcopy(bc->bcache_data + (bcache_blksize * BHASH(bc, blk)) + offset,
+ buf, size);
+ result = 0;
+ }
done:
if ((result == 0) && (rsize != NULL))
@@ -349,8 +372,16 @@ bcache_strategy(void *devdata, int rw, d
ret = read_strategy(devdata, rw, blk, offset,
csize, buf+total, &isize);
- if (ret != 0)
- return (ret);
+
+ /*
+ * we may have error from read ahead, if we have read some data
+ * return partial read.
+ */
+ if (ret != 0 || isize == 0) {
+ if (total != 0)
+ ret = 0;
+ break;
+ }
blk += (offset+isize) / bcache_blksize;
offset = 0;
total += isize;
Modified: head/sys/boot/efi/libefi/efipart.c
==============================================================================
--- head/sys/boot/efi/libefi/efipart.c Sun May 1 20:57:10 2016 (r298899)
+++ head/sys/boot/efi/libefi/efipart.c Sun May 1 21:06:59 2016 (r298900)
@@ -321,6 +321,15 @@ efipart_realstrategy(void *devdata, int
if (size == 0 || (size % 512) != 0)
return (EIO);
+ off = blk * 512;
+ /* make sure we don't read past disk end */
+ if ((off + size) / blkio->Media->BlockSize - 1 >
+ blkio->Media->LastBlock) {
+ size = blkio->Media->LastBlock + 1 -
+ off / blkio->Media->BlockSize;
+ size = size * blkio->Media->BlockSize;
+ }
+
if (rsize != NULL)
*rsize = size;
@@ -335,7 +344,6 @@ efipart_realstrategy(void *devdata, int
return (ENOMEM);
error = 0;
- off = blk * 512;
blk = off / blkio->Media->BlockSize;
blkoff = off % blkio->Media->BlockSize;
blksz = blkio->Media->BlockSize - blkoff;
Modified: head/sys/boot/i386/libi386/bioscd.c
==============================================================================
--- head/sys/boot/i386/libi386/bioscd.c Sun May 1 20:57:10 2016 (r298899)
+++ head/sys/boot/i386/libi386/bioscd.c Sun May 1 21:06:59 2016 (r298900)
@@ -271,14 +271,25 @@ bc_realstrategy(void *devdata, int rw, d
if (rsize)
*rsize = 0;
- if (blks && bc_read(unit, dblk, blks, buf)) {
+ if ((blks = bc_read(unit, dblk, blks, buf)) < 0) {
DEBUG("read error");
return (EIO);
+ } else {
+ if (size / BIOSCD_SECSIZE > blks) {
+ if (rsize)
+ *rsize = blks * BIOSCD_SECSIZE;
+ return (0);
+ }
}
#ifdef BD_SUPPORT_FRAGS
DEBUG("frag read %d from %lld+%d to %p",
fragsize, dblk, blks, buf + (blks * BIOSCD_SECSIZE));
- if (fragsize && bc_read(unit, dblk + blks, 1, fragbuf)) {
+ if (fragsize && bc_read(unit, dblk + blks, 1, fragbuf) != 1) {
+ if (blks) {
+ if (rsize)
+ *rsize = blks * BIOSCD_SECSIZE;
+ return (0);
+ }
DEBUG("frag read error");
return(EIO);
}
@@ -292,6 +303,7 @@ bc_realstrategy(void *devdata, int rw, d
/* Max number of sectors to bounce-buffer at a time. */
#define CD_BOUNCEBUF 8
+/* return negative value for an error, otherwise blocks read */
static int
bc_read(int unit, daddr_t dblk, int blks, caddr_t dest)
{
@@ -368,6 +380,8 @@ bc_read(int unit, daddr_t dblk, int blks
result = V86_CY(v86.efl);
if (result == 0)
break;
+ /* fall back to 1 sector read */
+ x = 1;
}
#ifdef DISK_DEBUG
@@ -376,6 +390,11 @@ bc_read(int unit, daddr_t dblk, int blks
DEBUG("%d sectors from %lld to %p (0x%x) %s", x, dblk, p,
VTOP(p), result ? "failed" : "ok");
DEBUG("unit %d status 0x%x", unit, error);
+
+ /* still an error? break off */
+ if (result != 0)
+ break;
+
if (bbuf != NULL)
bcopy(bbuf, p, x * BIOSCD_SECSIZE);
p += (x * BIOSCD_SECSIZE);
@@ -384,7 +403,11 @@ bc_read(int unit, daddr_t dblk, int blks
}
/* hexdump(dest, (blks * BIOSCD_SECSIZE)); */
- return(0);
+
+ if (blks - resid == 0)
+ return (-1); /* read failed */
+
+ return (blks - resid);
}
/*
Modified: head/sys/boot/i386/libi386/biosdisk.c
==============================================================================
--- head/sys/boot/i386/libi386/biosdisk.c Sun May 1 20:57:10 2016 (r298899)
+++ head/sys/boot/i386/libi386/biosdisk.c Sun May 1 21:06:59 2016 (r298900)
@@ -508,6 +508,18 @@ bd_realstrategy(void *devdata, int rw, d
if (rsize)
*rsize = 0;
+ if (dblk >= BD(dev).bd_sectors) {
+ DEBUG("IO past disk end %llu", (unsigned long long)dblk);
+ return (EIO);
+ }
+
+ if (dblk + blks > BD(dev).bd_sectors) {
+ /* perform partial read */
+ blks = BD(dev).bd_sectors - dblk;
+ size = blks * BD(dev).bd_sectorsize;
+ DEBUG("short read %d", blks);
+ }
+
switch(rw){
case F_READ:
DEBUG("read %d from %lld to %p", blks, dblk, buf);
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