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Index: head/sys/boot/common/bcache.c
===================================================================
--- head/sys/boot/common/bcache.c
+++ head/sys/boot/common/bcache.c
@@ -64,7 +64,7 @@
struct bcache {
struct bcachectl *bcache_ctl;
caddr_t bcache_data;
- u_int bcache_nblks;
+ size_t bcache_nblks;
size_t ra;
};
@@ -86,6 +86,7 @@
((bc)->bcache_ctl[BHASH((bc), (blkno))].bc_blkno != (blkno))
#define BCACHE_READAHEAD 256
#define BCACHE_MINREADAHEAD 32
+#define BCACHE_MARKER 0xdeadbeef
static void bcache_invalidate(struct bcache *bc, daddr_t blkno);
static void bcache_insert(struct bcache *bc, daddr_t blkno);
@@ -95,7 +96,7 @@
* Initialise the cache for (nblks) of (bsize).
*/
void
-bcache_init(u_int nblks, size_t bsize)
+bcache_init(size_t nblks, size_t bsize)
{
/* set up control data */
bcache_total_nblks = nblks;
@@ -122,6 +123,7 @@
u_int i;
struct bcache *bc = malloc(sizeof (struct bcache));
int disks = bcache_numdev;
+ uint32_t *marker;
if (disks == 0)
disks = 1; /* safe guard */
@@ -140,11 +142,13 @@
bc->bcache_nblks = bcache_total_nblks >> i;
bcache_unit_nblks = bc->bcache_nblks;
- bc->bcache_data = malloc(bc->bcache_nblks * bcache_blksize);
+ bc->bcache_data = malloc(bc->bcache_nblks * bcache_blksize +
+ sizeof(uint32_t));
if (bc->bcache_data == NULL) {
/* dont error out yet. fall back to 32 blocks and try again */
bc->bcache_nblks = 32;
- bc->bcache_data = malloc(bc->bcache_nblks * bcache_blksize);
+ bc->bcache_data = malloc(bc->bcache_nblks * bcache_blksize +
+ sizeof(uint32_t));
}
bc->bcache_ctl = malloc(bc->bcache_nblks * sizeof(struct bcachectl));
@@ -152,8 +156,11 @@
if ((bc->bcache_data == NULL) || (bc->bcache_ctl == NULL)) {
bcache_free_instance(bc);
errno = ENOMEM;
- return(NULL);
+ return (NULL);
}
+ /* Insert cache end marker. */
+ marker = (uint32_t *)(bc->bcache_data + bc->bcache_nblks * bcache_blksize);
+ *marker = BCACHE_MARKER;
/* Flush the cache */
for (i = 0; i < bc->bcache_nblks; i++) {
@@ -215,6 +222,9 @@
int result;
daddr_t p_blk;
caddr_t p_buf;
+ uint32_t *marker;
+
+ marker = (uint32_t *)(bc->bcache_data + bc->bcache_nblks * bcache_blksize);
if (bc == NULL) {
errno = ENODEV;
@@ -261,9 +271,35 @@
p_size = MIN(r_size, nblk - i); /* read at least those blocks */
+ /*
+ * The read ahead size setup.
+ * While the read ahead can save us IO, it also can complicate things:
+ * 1. We do not want to read ahead by wrapping around the
+ * bcache end - this would complicate the cache management.
+ * 2. We are using bc->ra as dynamic hint for read ahead size,
+ * detected cache hits will increase the read-ahead block count, and
+ * misses will decrease, see the code above.
+ * 3. The bcache is sized by 512B blocks, however, the underlying device
+ * may have a larger sector size, and we should perform the IO by
+ * taking into account these larger sector sizes. We could solve this by
+ * passing the sector size to bcache_allocate(), or by using ioctl(), but
+ * in this version we are using the constant, 16 blocks, and are rounding
+ * read ahead block count down to multiple of 16.
+ * Using the constant has two reasons, we are not entirely sure if the
+ * BIOS disk interface is providing the correct value for sector size.
+ * And secondly, this way we get the most conservative setup for the ra.
+ *
+ * The selection of multiple of 16 blocks (8KB) is quite arbitrary, however,
+ * we want to have the CD (2K) and the 4K disks to be covered.
+ * Also, as we have 32 blocks to be allocated as the fallback value in the
+ * bcache_allocate(), the 16 ra blocks will allow the read ahead
+ * to be used even with bcache this small.
+ */
+
ra = bc->bcache_nblks - BHASH(bc, p_blk + p_size);
- if (ra != bc->bcache_nblks) { /* do we have RA space? */
- ra = MIN(bc->ra, ra);
+ if (ra != 0 && ra != bc->bcache_nblks) { /* do we have RA space? */
+ ra = MIN(bc->ra, ra - 1);
+ ra = rounddown(ra, 16); /* multiple of 16 blocks */
p_size += ra;
}
@@ -310,6 +346,12 @@
result = 0;
}
+ if (*marker != BCACHE_MARKER) {
+ printf("BUG: bcache corruption detected: nblks: %zu p_blk: %lu, "
+ "p_size: %zu, ra: %zu\n", bc->bcache_nblks,
+ (long unsigned)BHASH(bc, p_blk), p_size, ra);
+ }
+
done:
if ((result == 0) && (rsize != NULL))
*rsize = size;
@@ -338,7 +380,7 @@
/* bypass large requests, or when the cache is inactive */
if (bc == NULL ||
((size * 2 / bcache_blksize) > bcache_nblks)) {
- DEBUG("bypass %d from %d", size / bcache_blksize, blk);
+ DEBUG("bypass %zu from %qu", size / bcache_blksize, blk);
bcache_bypasses++;
return (dd->dv_strategy(dd->dv_devdata, rw, blk, size, buf, rsize));
}
Index: head/sys/boot/common/bootstrap.h
===================================================================
--- head/sys/boot/common/bootstrap.h
+++ head/sys/boot/common/bootstrap.h
@@ -73,7 +73,7 @@
void *alloc_pread(int fd, off_t off, size_t len);
/* bcache.c */
-void bcache_init(u_int nblks, size_t bsize);
+void bcache_init(size_t nblks, size_t bsize);
void bcache_add_dev(int);
void *bcache_allocate(void);
void bcache_free(void *);

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