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Merged
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Jul 27, 2025
Merged

Boost the remove operation #74

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159d64f
Adjust unit tests
RoyWFHuang Jul 20, 2025
0c50fb5
Use nr_blk to record the cont. blks in ext
RoyWFHuang Jul 27, 2025
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69 changes: 37 additions & 32 deletions README.md
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -101,48 +101,53 @@ on the type of file:
```
inode
+-----------------------+
| i_mode = IFDIR | 0755 | block 123
| ei_block = 123 ----|--------> +----------------+
| i_size = 4 KiB | 0 | ee_block = 0 |
| i_blocks = 1 | | ee_len = 8 | block 84
+-----------------------+ | ee_start = 84 |---> +-----------+
|----------------| 0 | 24 (foo) |
1 | ee_block = 8 | |-----------|
| ee_len = 8 | 1 | 45 (bar) |
| ee_start = 16 | |-----------|
|----------------| | ... |
| ... | |-----------|
|----------------| 14 | 0 |
341 | ee_block = 0 | +-----------+
| ee_len = 0 |
| ee_start = 0 |
+----------------+
| i_mode = IFDIR | 0755 | block 123 (simplefs_file_ei_block)
| ei_block = 123 ----|---> +----------------+
| i_size = 4 KiB | | nr_files = 7 |
| i_blocks = 1 | |----------------|
+-----------------------+ 0 | ee_block = 0 |
| ee_len = 8 | block 84(simplefs_dir_block)
| ee_start = 84 |---> +-------------+
| nr_file = 2 | |nr_files = 2 |
|----------------| |-------------|
1 | ee_block = 8 | 0 | inode = 24 |
| ee_len = 8 | | nr_blk = 1 |
| ee_start = 16 | | (foo) |
| nr_file = 5 | |-------------|
|----------------| 1 | inode = 45 |
| ... | | nr_blk = 14 |
|----------------| | (bar) |
341 | ee_block = 0 | |-------------|
| ee_len = 0 | | ... |
| ee_start = 0 | |-------------|
| nr_file = 12 | 14 | 0 |
+----------------+ +-------------+

```
- For a file, it lists the extents that hold the actual data of the file.
Given that block IDs are stored as values of `sizeof(struct simplefs_extent)`
bytes, a single block can accommodate up to 341 links. This limitation
restricts the maximum size of a file to approximately 10.65 MiB (10,912 KiB).
```
inode
+-----------------------+
| i_mode = IFDIR | 0644 | block 93
| ei_block = 93 ----|------> +----------------+
| i_size = 10 KiB | 0 | ee_block = 0 |
| i_blocks = 25 | | ee_len = 8 | extent 94
inode
+-----------------------+
| i_mode = IFDIR | 0644 | block 93
| ei_block = 93 ----|------> +----------------+
| i_size = 10 KiB | 0 | ee_block = 0 |
| i_blocks = 25 | | ee_len = 8 | extent 94
+-----------------------+ | ee_start = 94 |---> +--------+
|----------------| | |
|----------------| | |
1 | ee_block = 8 | +--------+
| ee_len = 8 | extent 99
| ee_start = 99 |---> +--------+
| ee_start = 99 |---> +--------+
|----------------| | |
2 | ee_block = 16 | +--------+
| ee_len = 8 | extent 66
| ee_len = 8 | extent 66
| ee_start = 66 |---> +--------+
|----------------| | |
| ... | +--------+
|----------------|
341 | ee_block = 0 |
|----------------|
341 | ee_block = 0 |
| ee_len = 0 |
| ee_start = 0 |
+----------------+
Expand All @@ -158,8 +163,8 @@ comprises three members:

```
struct simplefs_extent
+----------------+
| ee_block = 0 |
+----------------+
| ee_block = 0 |
| ee_len = 200| extent
| ee_start = 12 |-----------> +---------+
+----------------+ block 12 | |
Expand All @@ -181,7 +186,7 @@ The journaling support in simplefs is implemented using the jbd2 subsystem, whic

For a detailed introduction to journaling, please refer to these two websites:
[Journal(jbd2) document](https://www.kernel.org/doc/html/latest/filesystems/ext4/journal.html)
[Journal(jbd2) api](https://docs.kernel.org/filesystems/journalling.html)
[Journal(jbd2) api](https://docs.kernel.org/filesystems/journalling.html)

External journal device disk layout:

Expand All @@ -193,12 +198,12 @@ Hint:
Each transaction starts with a descriptor block, followed by several metadata blocks or data blocks, and ends with a commit block. Every modified metadata (such as inode, bitmap, etc.) occupies its own block. Currently, simplefs primarily records "extent" metadata.


How to Enable Journaling in simplefs:
How to Enable Journaling in simplefs:

Step 1: Create the Journal Disk Image
To create an 8MB disk image for the journal, use the following make command:

Note:
Note:
Assuming an 8 MB size for the external journal device, which is an arbitrary choice for now, I will set the journal block length to a fixed 2048, calculated by dividing the device size by the block size (4096 bytes).

```shell
Expand Down
3 changes: 2 additions & 1 deletion bitmap.h
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Original file line number Diff line number Diff line change
Expand Up @@ -52,8 +52,9 @@ static inline uint32_t get_free_blocks(struct super_block *sb, uint32_t len)
return 0;

sbi->nr_free_blocks -= len;
struct buffer_head *bh;
for (i = 0; i < len; i++) {
struct buffer_head *bh = sb_bread(sb, ret + i);
bh = sb_bread(sb, ret + i);
if (!bh) {
pr_err("get_free_blocks: sb_bread failed for block %d\n", ret + i);
sbi->nr_free_blocks += len;
Expand Down
59 changes: 42 additions & 17 deletions dir.c
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,6 @@ static int simplefs_iterate(struct file *dir, struct dir_context *ctx)
struct buffer_head *bh = NULL, *bh2 = NULL;
struct simplefs_file_ei_block *eblock = NULL;
struct simplefs_dir_block *dblock = NULL;
struct simplefs_file *f = NULL;
int ei = 0, bi = 0, fi = 0;
int ret = 0;

Expand All @@ -43,36 +42,62 @@ static int simplefs_iterate(struct file *dir, struct dir_context *ctx)
return -EIO;
eblock = (struct simplefs_file_ei_block *) bh->b_data;

ei = (ctx->pos - 2) / SIMPLEFS_FILES_PER_EXT;
bi = (ctx->pos - 2) % SIMPLEFS_FILES_PER_EXT / SIMPLEFS_FILES_PER_BLOCK;
fi = (ctx->pos - 2) % SIMPLEFS_FILES_PER_BLOCK;
if (ctx->pos - 2 == eblock->nr_files)
goto release_bh;

/* Iterate over the index block and commit subfiles */
for (; ei < SIMPLEFS_MAX_EXTENTS; ei++) {
int remained_nr_files = eblock->nr_files - (ctx->pos - 2);

int offset = ctx->pos - 2;
for (ei = 0; ei < SIMPLEFS_MAX_EXTENTS; ei++) {
if (eblock->extents[ei].ee_start == 0)
continue;
if (offset > eblock->extents[ei].nr_files) {
offset -= eblock->extents[ei].nr_files;
} else {
break;
}
}

/* Iterate over the index block and commit subfiles */
for (; remained_nr_files && ei < SIMPLEFS_MAX_EXTENTS; ei++) {
if (eblock->extents[ei].ee_start == 0)
continue;

/* Iterate over blocks in one extent */
for (; bi < eblock->extents[ei].ee_len; bi++) {
for (bi = 0; bi < eblock->extents[ei].ee_len && remained_nr_files;
bi++) {
bh2 = sb_bread(sb, eblock->extents[ei].ee_start + bi);
if (!bh2) {
ret = -EIO;
goto release_bh;
}
dblock = (struct simplefs_dir_block *) bh2->b_data;
if (dblock->files[0].inode == 0) {

if (offset > dblock->nr_files) {
offset -= dblock->nr_files;
brelse(bh2);
bh2 = NULL;
break;
continue;
}
/* Iterate every file in one block */
for (; fi < SIMPLEFS_FILES_PER_BLOCK; fi++) {
f = &dblock->files[fi];
if (f->inode &&
!dir_emit(ctx, f->filename, SIMPLEFS_FILENAME_LEN, f->inode,
DT_UNKNOWN))
break;
ctx->pos++;

for (fi = 0; fi < SIMPLEFS_FILES_PER_BLOCK;) {
if (dblock->files[fi].inode != 0) {
if (offset) {
offset--;
} else {
remained_nr_files--;
if (!dir_emit(ctx, dblock->files[fi].filename,
SIMPLEFS_FILENAME_LEN,
dblock->files[fi].inode, DT_UNKNOWN)) {
brelse(bh2);
bh2 = NULL;
goto release_bh;
}

ctx->pos++;
}
}
fi += dblock->files[fi].nr_blk;
}
brelse(bh2);
bh2 = NULL;
Expand Down
8 changes: 4 additions & 4 deletions file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -51,14 +51,14 @@ static int simplefs_file_get_block(struct inode *inode,
ret = 0;
goto brelse_index;
}
bno = get_free_blocks(sb, 8);
bno = get_free_blocks(sb, SIMPLEFS_MAX_BLOCKS_PER_EXTENT);
if (!bno) {
ret = -ENOSPC;
goto brelse_index;
}

index->extents[extent].ee_start = bno;
index->extents[extent].ee_len = 8;
index->extents[extent].ee_len = SIMPLEFS_MAX_BLOCKS_PER_EXTENT;
index->extents[extent].ee_block =
extent ? index->extents[extent - 1].ee_block +
index->extents[extent - 1].ee_len
Expand Down Expand Up @@ -386,13 +386,13 @@ static ssize_t simplefs_write(struct file *file,
while (len > 0) {
/* check if block is allocated */
if (ei_block->extents[ei_index].ee_start == 0) {
int bno = get_free_blocks(sb, 8);
int bno = get_free_blocks(sb, SIMPLEFS_MAX_BLOCKS_PER_EXTENT);
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_len = SIMPLEFS_MAX_BLOCKS_PER_EXTENT;
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
Expand Down
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