/*===========================================================================*
* read_block *
*===========================================================================*/
static void read_block(
struct buf *bp /* buffer pointer */
)
{
/* Read or write a disk block. This is the only routine in which actual disk
* I/O is invoked. If an error occurs, a message is printed here, but the error
* is not reported to the caller. If the error occurred while purging a block
* from the cache, it is not clear what the caller could do about it anyway.
*/
int r, op_failed;
off_t pos;
dev_t dev = bp->lmfs_dev;
op_failed = 0;
assert(dev != NO_DEV);
ASSERT(bp->lmfs_bytes == fs_block_size);
ASSERT(fs_block_size > 0);
pos = (off_t)bp->lmfs_blocknr * fs_block_size;
if(fs_block_size > PAGE_SIZE) {
#define MAXPAGES 20
vir_bytes blockrem, vaddr = (vir_bytes) bp->data;
int p = 0;
static iovec_t iovec[MAXPAGES];
blockrem = fs_block_size;
while(blockrem > 0) {
vir_bytes chunk = blockrem >= PAGE_SIZE ? PAGE_SIZE : blockrem;
iovec[p].iov_addr = vaddr;
iovec[p].iov_size = chunk;
vaddr += chunk;
blockrem -= chunk;
p++;
}
r = bdev_gather(dev, pos, iovec, p, BDEV_NOFLAGS);
} else {
r = bdev_read(dev, pos, bp->data, fs_block_size,
BDEV_NOFLAGS);
}
if (r < 0) {
printf("fs cache: I/O error on device %d/%d, block %u\n",
major(dev), minor(dev), bp->lmfs_blocknr);
op_failed = 1;
} else if (r != (ssize_t) fs_block_size) {
r = END_OF_FILE;
op_failed = 1;
}
if (op_failed) {
bp->lmfs_dev = NO_DEV; /* invalidate block */
/* Report read errors to interested parties. */
rdwt_err = r;
}
}
/*===========================================================================*
* read_block *
*===========================================================================*/
static int read_block(struct buf *bp, size_t block_size)
{
/* Read a disk block of 'size' bytes. The given size is always the FS block
* size, except for the last block of a device. If an I/O error occurs,
* invalidate the block and return an error code.
*/
ssize_t r;
off_t pos;
dev_t dev = bp->lmfs_dev;
assert(dev != NO_DEV);
ASSERT(bp->lmfs_bytes == block_size);
ASSERT(fs_block_size > 0);
pos = (off_t)bp->lmfs_blocknr * fs_block_size;
if (block_size > PAGE_SIZE) {
#define MAXPAGES 20
vir_bytes blockrem, vaddr = (vir_bytes) bp->data;
int p = 0;
static iovec_t iovec[MAXPAGES];
blockrem = block_size;
while(blockrem > 0) {
vir_bytes chunk = blockrem >= PAGE_SIZE ? PAGE_SIZE : blockrem;
iovec[p].iov_addr = vaddr;
iovec[p].iov_size = chunk;
vaddr += chunk;
blockrem -= chunk;
p++;
}
r = bdev_gather(dev, pos, iovec, p, BDEV_NOFLAGS);
} else {
r = bdev_read(dev, pos, bp->data, block_size, BDEV_NOFLAGS);
}
if (r != (ssize_t)block_size) {
/* Aesthetics: do not report EOF errors on superblock reads, because
* this is a fairly common occurrence, e.g. during system installation.
*/
if (bp->lmfs_blocknr != 0 /*first block*/ || r != 0 /*EOF*/)
printf("fs cache: I/O error on device %d/%d, block %"PRIu64
" (%zd)\n", major(dev), minor(dev), bp->lmfs_blocknr, r);
if (r >= 0)
r = EIO; /* TODO: retry retrieving (just) the remaining part */
bp->lmfs_dev = NO_DEV; /* invalidate block */
return r;
}
return OK;
}
/*===========================================================================*
* rw_block *
*===========================================================================*/
static void rw_block(
register struct buf *bp, /* buffer pointer */
int rw_flag /* READING or WRITING */
)
{
/* Read or write a disk block. This is the only routine in which actual disk
* I/O is invoked. If an error occurs, a message is printed here, but the error
* is not reported to the caller. If the error occurred while purging a block
* from the cache, it is not clear what the caller could do about it anyway.
*/
int r, op_failed = 0;
u64_t pos;
dev_t dev;
if ( (dev = bp->b_dev) != NO_DEV) {
pos = mul64u(bp->b_blocknr, fs_block_size);
if (rw_flag == READING)
r = bdev_read(dev, pos, bp->b_data, fs_block_size,
BDEV_NOFLAGS);
else
r = bdev_write(dev, pos, bp->b_data, fs_block_size,
BDEV_NOFLAGS);
if (r < 0) {
printf("Ext2(%d) I/O error on device %d/%d, block %u\n",
SELF_E, major(dev), minor(dev), bp->b_blocknr);
op_failed = 1;
} else if (r != (ssize_t) fs_block_size) {
r = END_OF_FILE;
op_failed = 1;
}
if (op_failed) {
bp->b_dev = NO_DEV; /* invalidate block */
/* Report read errors to interested parties. */
if (rw_flag == READING) rdwt_err = r;
}
}
bp->b_dirt = CLEAN;
}
/*
* Reads from a file.
*/
PUBLIC ssize_t sys_read(int fd, void *buf, size_t n)
{
dev_t dev; /* Device number. */
struct file *f; /* File. */
struct inode *i; /* Inode. */
ssize_t count; /* Bytes actually read. */
/* Invalid file descriptor. */
if ((fd < 0) || (fd >= OPEN_MAX) || ((f = curr_proc->ofiles[fd]) == NULL))
return (-EBADF);
/* File not opened for reading. */
if (ACCMODE(f->oflag) == O_WRONLY)
return (-EBADF);
#if (EDUCATIONAL_KERNEL == 0)
/* Invalid buffer. */
if (!chkmem(buf, n, MAY_WRITE))
return (-EINVAL);
#endif
/* Nothing to do. */
if (n == 0)
return (0);
i = f->inode;
/* Character special file. */
if (S_ISCHR(i->mode))
{
dev = i->blocks[0];
count = cdev_read(dev, buf, n);
return (count);
}
/* Block special file. */
else if (S_ISBLK(i->mode))
{
dev = i->blocks[0];
count = bdev_read(dev, buf, n, f->pos);
}
/* Pipe file. */
else if (S_ISFIFO(i->mode))
{
kprintf("read from pipe");
count = pipe_read(i, buf, n);
}
/* Regular file/directory. */
else if ((S_ISDIR(i->mode)) || (S_ISREG(i->mode)))
count = file_read(i, buf, n, f->pos);
/* Unknown file type. */
else
return (-EINVAL);
/* Failed to read. */
if (count < 0)
return (curr_proc->errno);
inode_touch(i);
f->pos += count;
return (count);
}
