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Reimplement the read and the write operations #62

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Merged
merged 1 commit into from
Jun 25, 2024
Merged

Reimplement the read and the write operations #62

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172 changes: 168 additions & 4 deletions file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -255,7 +255,7 @@ static int simplefs_write_end(struct file *file,
* over the data block pointers, releasing the associated data blocks, and
* updating the inode metadata (size and block count).
*/
static int simplefs_file_open(struct inode *inode, struct file *filp)
static int simplefs_open(struct inode *inode, struct file *filp)
{
bool wronly = (filp->f_flags & O_WRONLY);
bool rdwr = (filp->f_flags & O_RDWR);
Expand Down Expand Up @@ -293,6 +293,170 @@ static int simplefs_file_open(struct inode *inode, struct file *filp)
return 0;
}

static ssize_t simplefs_read(struct file *file,
char __user *buf,
size_t len,
loff_t *ppos)
{
struct inode *inode = file_inode(file);
struct super_block *sb = inode->i_sb;
ssize_t bytes_read = 0;
loff_t pos = *ppos;

if (pos > inode->i_size)
return 0;

/* find extent block */
struct buffer_head *bh = sb_bread(sb, SIMPLEFS_INODE(inode)->ei_block);
struct simplefs_file_ei_block *ei_block =
(struct simplefs_file_ei_block *) bh->b_data;


if (pos + len > inode->i_size)
len = inode->i_size - pos;

/* count block position */
sector_t block_index = pos / SIMPLEFS_BLOCK_SIZE;
sector_t ei_index = block_index / SIMPLEFS_MAX_BLOCKS_PER_EXTENT;
sector_t block_offset = ei_block->extents[ei_index].ee_start +
block_index % SIMPLEFS_MAX_BLOCKS_PER_EXTENT;

while (len > 0) {
struct buffer_head *bh_data = sb_bread(sb, block_offset);
if (!bh_data) {
pr_err("Failed to read data block %llu\n", block_offset);
bytes_read = -EIO;
break;
}

size_t offset = pos % SIMPLEFS_BLOCK_SIZE;
size_t bytes_to_read =
min_t(size_t, len, SIMPLEFS_BLOCK_SIZE - pos % SIMPLEFS_BLOCK_SIZE);
if (copy_to_user(buf + bytes_read, bh_data->b_data + offset,
bytes_to_read)) {
brelse(bh_data);
bytes_read = -EFAULT;
break;
}
brelse(bh_data);

/* successfully read data */
bytes_read += bytes_to_read;
len -= bytes_to_read;
pos += bytes_to_read;

/* count extent block */
block_index++;
ei_index = block_index / SIMPLEFS_MAX_BLOCKS_PER_EXTENT;
block_offset = ei_block->extents[ei_index].ee_start +
block_index % SIMPLEFS_MAX_BLOCKS_PER_EXTENT;
}

brelse(bh);
*ppos = pos;

return bytes_read;
}

static ssize_t simplefs_write(struct file *file,
const char __user *buf,
size_t len,
loff_t *ppos)
{
struct inode *inode = file_inode(file);
struct super_block *sb = inode->i_sb;
ssize_t bytes_write = 0;
loff_t pos = *ppos;

if (pos > inode->i_size)
return 0;
len = min_t(size_t, len, SIMPLEFS_MAX_FILESIZE - pos);

/* find extent block */
struct buffer_head *bh = sb_bread(sb, SIMPLEFS_INODE(inode)->ei_block);
if (!bh)
return -EIO;
struct simplefs_file_ei_block *ei_block =
(struct simplefs_file_ei_block *) bh->b_data;

/* count block position */
sector_t block_index = pos / SIMPLEFS_BLOCK_SIZE;
sector_t ei_index = block_index / SIMPLEFS_MAX_BLOCKS_PER_EXTENT;

/* write data */
while (len > 0) {
/* check if block is allocated */
if (ei_block->extents[ei_index].ee_start == 0) {
int bno = get_free_blocks(sb, 8);
if (!bno) {
bytes_write = -ENOSPC;
break;
}
ei_block->extents[ei_index].ee_start = bno;
ei_block->extents[ei_index].ee_len = 8;
ei_block->extents[ei_index].ee_block =
ei_index ? ei_block->extents[ei_index - 1].ee_block +
ei_block->extents[ei_index - 1].ee_len
: 0;
}

struct buffer_head *bh_data =
sb_bread(sb, ei_block->extents[ei_index].ee_start +
block_index % SIMPLEFS_MAX_BLOCKS_PER_EXTENT);
if (!bh_data) {
pr_err("Failed to read data block %llu\n",
ei_block->extents[ei_index].ee_start +
block_index % SIMPLEFS_MAX_BLOCKS_PER_EXTENT);
bytes_write = -EIO;
break;
}
/* copy data from buffer */
size_t bytes_to_write =
min_t(size_t, len, SIMPLEFS_BLOCK_SIZE - pos % SIMPLEFS_BLOCK_SIZE);

if (copy_from_user(bh_data->b_data + pos % SIMPLEFS_BLOCK_SIZE, buf,
bytes_to_write)) {
brelse(bh_data);
bytes_write = -EFAULT;
break;
}

mark_buffer_dirty(bh_data);
sync_dirty_buffer(bh_data);
brelse(bh_data);

/* successfully write data */
len = len - bytes_to_write;
bytes_write += bytes_to_write;
pos += bytes_to_write;

/* count extent block */
block_index = pos / SIMPLEFS_BLOCK_SIZE;
ei_index = block_index / SIMPLEFS_MAX_BLOCKS_PER_EXTENT;
}
mark_buffer_dirty(bh);
sync_dirty_buffer(bh);
brelse(bh);

inode->i_size = max(pos, inode->i_size);
inode->i_blocks = DIV_ROUND_UP(inode->i_size, SIMPLEFS_BLOCK_SIZE) + 1;
#if SIMPLEFS_AT_LEAST(6, 7, 0)
struct timespec64 cur_time = current_time(inode);
inode_set_mtime_to_ts(inode, cur_time);
inode_set_ctime_to_ts(inode, cur_time);
#elif SIMPLEFS_AT_LEAST(6, 6, 0)
struct timespec64 cur_time = current_time(inode);
inode->i_mtime = cur_time;
inode_set_ctime_to_ts(inode, cur_time);
#else
inode->i_mtime = inode->i_ctime = current_time(inode);
#endif
mark_inode_dirty(inode);
*ppos = pos;

return bytes_write;
}

const struct address_space_operations simplefs_aops = {
#if SIMPLEFS_AT_LEAST(5, 19, 0)
.readahead = simplefs_readahead,
Expand All @@ -307,8 +471,8 @@ const struct address_space_operations simplefs_aops = {
const struct file_operations simplefs_file_ops = {
.llseek = generic_file_llseek,
.owner = THIS_MODULE,
.read_iter = generic_file_read_iter,
.write_iter = generic_file_write_iter,
.fsync = generic_file_fsync,
.open = simplefs_file_open,
.open = simplefs_open,
.read = simplefs_read,
.write = simplefs_write,
};
2 changes: 2 additions & 0 deletions simplefs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,8 @@
#define SIMPLEFS_MAX_EXTENTS \
((SIMPLEFS_BLOCK_SIZE - sizeof(uint32_t)) / sizeof(struct simplefs_extent))
#define SIMPLEFS_MAX_BLOCKS_PER_EXTENT 8 /* It can be ~(uint32) 0 */
#define SIMPLEFS_MAX_SIZES_PER_EXTENT \
(SIMPLEFS_MAX_BLOCKS_PER_EXTENT * SIMPLEFS_BLOCK_SIZE)
#define SIMPLEFS_MAX_FILESIZE \
((uint64_t) SIMPLEFS_MAX_BLOCKS_PER_EXTENT * SIMPLEFS_BLOCK_SIZE * \
SIMPLEFS_MAX_EXTENTS)
Expand Down