分类： LINUX
ubidesign.pdf
A Brief Introduction to the Design of UBIFS.pdf
我们按照挂载ubifs的工序来分析代码：
（1）ubiattach /dev/ubi_ctrl -m 3
（2）ubimkvol /dev/ubi0 -N ubifs -s15MiB
（3）mount -t ubifs ubi0:ubifs /mnt
首先先分析（1），相应的代码是ubi_attach_mtd_dev（）函数，下面我们紧跟代码来看看究竟干了些什么。
1．ubi_attach_mtd_devint ubi_attach_mtd_dev(struct mtd_info*mtd, int ubi_num, int vid_hdr_offset)
{
//ubi_num, vid_hdr_offset是命令传进来的参数
structubi_device *ubi;
inti, err, do_free = 1;
/*
* Check if we already have the same MTD deviceattached.
*
* Note, this function assumes that UBI devicescreations and deletions
* are serialized, so it does not take the&ubi_devices_lock.
*/
for(i = 0; i < UBI_MAX_DEVICES; i++) {
ubi= ubi_devices[i];
if(ubi && mtd->index == ubi->mtd->index) {
dbg_err("mtd%dis already attached to ubi%d",
mtd->index,i);
return-EEXIST;
}
}
//上面的这段代码可以看英文注释，一个mtd设备（一个分区）不能被attach两次，除非你已经deatch了。所以在这段代码的开始就检查被attach的mtd设备是否已经被attach了。
if(mtd->type == MTD_UBIVOLUME) {
ubi_err("refuseattaching mtd%d - it is already emulated on "
"topof UBI", mtd->index);
return-EINVAL;
}
上面的代码接着检查被attach的mtd设备时候是一个mtdvolume（卷区），如果已经是一个mtd卷了，那么就不能再被attach了。
if (ubi_num == UBI_DEV_NUM_AUTO) {
/*Search for an empty slot in the @ubi_devices array */
for (ubi_num = 0; ubi_num < UBI_MAX_DEVICES;ubi_num++)
if (!ubi_devices[ubi_num])
break;
如果在终端输入命令的时候没有带ubinum，那么就是自动分配ubinum，系统就会从ubi_device[]数组中找出一个没被使用的ubinum号
if (ubi_num == UBI_MAX_DEVICES) {
dbg_err("only %d UBI devices may becreated",
return -ENFILE;
}
} else {
if (ubi_num >= UBI_MAX_DEVICES)
return -EINVAL;
如果ubi_num > UBI_MAX_DEVICES，就代表没有空余ubinum号可供分配，返回出错
/* Make sure ubi_num is not busy */
if (ubi_devices[ubi_num]) {
dbg_err("ubi%d already exists",ubi_num);
return -EEXIST;
}
}
ubi = kzalloc(sizeof(struct ubi_device), GFP_KERNEL);
if (!ubi)
return -ENOMEM;
ubi->mtd = mtd;
ubi->ubi_num = ubi_num;
ubi->vid_hdr_offset = vid_hdr_offset;
ubi->autoresize_vol_id = -1;
mutex_init(&ubi->buf_mutex);
mutex_init(&ubi->ckvol_mutex);
mutex_init(&ubi->mult_mutex);
mutex_init(&ubi->volumes_mutex);
spin_lock_init(&ubi->volumes_lock);
初始化信号
ubi_msg("attaching mtd%d to ubi%d", mtd->index,ubi_num);
err = io_init(ubi);
if (err)
goto out_free;
下面跟着io_init()往下分析：
static intio_init(struct ubi_device *ubi)
{
if (ubi->mtd->numeraseregions != 0) {
ubi_err("multiple regions, not implemented");
return -EINVAL;
}
Numeraseregions是扫描nandflash得到的信息，如果numeraseregions等于0，代表我们需要attach的设备已经擦除过了
if (ubi->vid_hdr_offset < 0)
return -EINVAL;
ubi->vid_hdr_offset显然应该是一个正数，一般是nandflash的一页，我们的4020上的nandflash页大小为512字节，所以ubi->vid_hdr_offset为512.这儿再稍微说一下，EC header和VID header，是记录我们ubi管理信息。一般EC在一个擦除块的第一页，所以偏移量为0，VID在擦除块的第二页上，所以偏移量为512.，在我们4020的nandflash上，一个擦除块的大小为16K，也就是32页。
下面接着讲我们的扫描信息写进mtd结构体
ubi->peb_size =ubi->mtd->erasesize;
ubi->peb_count =ubi->mtd->size / ubi->mtd->erasesize;
Peb_count是指逻辑块的数目，也就是总的大小除以每一页的大小
ubi->flash_size = ubi->mtd->size;
if (ubi->mtd->block_isbad &&ubi->mtd->block_markbad)
ubi->bad_allowed = 1;
ubi->min_io_size = ubi->mtd->writesize;
ubi->hdrs_min_io_size = ubi->mtd->writesize >>ubi->mtd->subpage_sft;
if (!is_power_of_2(ubi->min_io_size)) {
ubi_err("min. I/O unit (%d) is not power of2",
ubi->min_io_size);
return -EINVAL;
}
ubi_assert(ubi->hdrs_min_io_size > 0);
ubi_assert(ubi->hdrs_min_io_size <=ubi->min_io_size);
ubi_assert(ubi->min_io_size % ubi->hdrs_min_io_size ==0);
/* Calculate defaultaligned sizes of EC and VID headers */
ubi->ec_hdr_alsize = ALIGN(UBI_EC_HDR_SIZE,ubi->hdrs_min_io_size);
ubi->vid_hdr_alsize = ALIGN(UBI_VID_HDR_SIZE,ubi->hdrs_min_io_size);
dbg_msg("min_io_size %d", ubi->min_io_size);
dbg_msg("hdrs_min_io_size %d",ubi->hdrs_min_io_size);
dbg_msg("ec_hdr_alsize %d", ubi->ec_hdr_alsize);
dbg_msg("vid_hdr_alsize %d", ubi->vid_hdr_alsize);
if (ubi->vid_hdr_offset == 0)
/* Default offset */
ubi->vid_hdr_offset = ubi->vid_hdr_aloffset =
ubi->ec_hdr_alsize;
else {
ubi->vid_hdr_aloffset = ubi->vid_hdr_offset &
~(ubi->hdrs_min_io_size- 1);
ubi->vid_hdr_shift = ubi->vid_hdr_offset -
ubi->vid_hdr_aloffset;
}
Io_init剩余的部分就不分析了，比较容易
接着上面ubi_attach_mtd_dev（）往下说：
ubi->peb_buf1 = vmalloc(ubi->peb_size);
if (!ubi->peb_buf1)
goto out_free;
ubi->peb_buf2 = vmalloc(ubi->peb_size);
if (!ubi->peb_buf2)
goto out_free;
分配两个物理擦除块大小的buf，具体的用途下面再说
err = attach_by_scanning(ubi);
if (err) {
dbg_err("failed to attach by scanning, error%d", err);
goto out_free;
}
我们再跟着attach_by_scanning(ubi)细说
static intattach_by_scanning(struct ubi_device *ubi)
{
int err;
struct ubi_scan_info *si;
si = ubi_scan(ubi);
**********************************************************************************
这儿通过ubi_scan函数来扫描MTD分区的每一块。具体是调用static intprocess_eb(struct ubi_device *ubi, struct ubi_scan_info *si,int pnum)函数来读取EC和VID头（即没一块的前两页），在读每一页的时候，会调用check_pattern函数来判断这一页是否为空，如果每一页都是空的，那么就会发现这个MTD分区是空的。
**********************************************************************************
if (IS_ERR(si))
return PTR_ERR(si);
ubi->bad_peb_count = si->bad_peb_count;
ubi->good_peb_count = ubi->peb_count -ubi->bad_peb_count;
ubi->max_ec = si->max_ec;
ubi->mean_ec = si->mean_ec;
err = ubi_read_volume_table(ubi, si);
if (err)
goto out_si;
err = ubi_wl_init_scan(ubi, si);
**********************************************************************************
取之ubi_wl_init_scan(ubi, si);函数片段
list_for_each_entry_safe(seb,tmp, &si->erase, u.list) {
cond_resched();
e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
if (!e)
goto out_free;
e->pnum = seb->pnum;
e->ec = seb->ec;
ubi->lookuptbl[e->pnum] = e;
if (schedule_erase(ubi, e, 0)) {
kmem_cache_free(ubi_wl_entry_slab, e);
goto out_free;
}
}
在初始化wl的时候会将为每一个空页建立一个struct ubi_work *wl_wrk;结构体（该结构体的具体处理函数为erase_worker，擦除一块，并写入EC头），并添加到ubi->works队列中（list_add_tail(&wrk->list,&ubi->works)）；这儿我们渐渐的认识到ubi->works这个队列的作用，后台进程ubi_thread就是循环的处理该队列中的工作的。
在第一次attach的时候，在这儿ubi_thread进程还没有被唤醒，所以这些工作要等到进程被唤醒的时候才能被处理
**********************************************************************************
if (err)
goto out_vtbl;
err =ubi_eba_init_scan(ubi, si);
**********************************************************************************
前面我们看到了ubi_scan，其实这个这个过程是建立ubifs的基础，因为所有关于ubi和ubifs的基本信息都是在scan 的过程中建立在内存中的，现在调用ubi_eba_init_scan来建立起EBA子系统就是利用前面的扫描信息，建立起没一个volumn的vtl。
if (err)
goto out_wl;
ubi_scan_destroy_si(si);
return 0;
out_wl:
ubi_wl_close(ubi);
out_vtbl:
free_internal_volumes(ubi);
vfree(ubi->vtbl);
out_si:
ubi_scan_destroy_si(si);
return err;
}
1.1．Ubi_scan
struct ubi_scan_info*ubi_scan(struct ubi_device *ubi)
{
int err, pnum;
struct rb_node *rb1, *rb2;
struct ubi_scan_volume *sv;
struct ubi_scan_leb *seb;
struct ubi_scan_info *si;
si = kzalloc(sizeof(struct ubi_scan_info), GFP_KERNEL);
if (!si)
return ERR_PTR(-ENOMEM);
INIT_LIST_HEAD(&si->corr);//初始化si的corrupt队列
INIT_LIST_HEAD(&si->free);// //初始化si的corrupt队列
INIT_LIST_HEAD(&si->erase);初始化si的corrupt队列
INIT_LIST_HEAD(&si->alien); //初始化si的corrupt队列
si->volumes = RB_ROOT;
si->is_empty = 1;
err = -ENOMEM;
ech = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);//为ec头部分配空间，用于暂存后面读出的每一个peb的ec头部信息
if (!ech)
goto out_si;
vidh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);//为vid头部分配空间，用于暂存后面读出的每一个peb的vid头部信息，注意扫描的目的就是收集EC和VID中信息，在内存中建立相关的信息
if (!vidh)
goto out_ech;
for (pnum = 0; pnum < ubi->peb_count; pnum++) {
cond_resched();
dbg_gen("process PEB %d", pnum);
err = process_eb(ubi, si, pnum);//具体的扫描每一个物理块
if (err < 0)
goto out_vidh;
}
dbg_msg("scanning is finished");
/* Calculate mean erase counter */
if (si->ec_count)//算平均擦除次数
si->mean_ec = div_u64(si->ec_sum,si->ec_count);
if (si->is_empty)//判断这是否是一个空的MTD，如果是空的话，那么后面的mount的时候调用create_default_filesystem在建立初始的ubifs数据
ubi_msg("empty MTD device detected");
/*
* Few corrupted PEBsare not a problem and may be just a result of
* unclean reboots.However, many of them may indicate some problems
* with the flash HW ordriver. Print a warning in this case.
*/
if (si->corr_count >= 8 || si->corr_count >=ubi->peb_count / 4) {
ubi_warn("%d PEBs are corrupted",si->corr_count);
printk(KERN_WARNING "corrupted PEBs are:");
list_for_each_entry(seb, &si->corr, u.list)
printk(KERN_CONT " %d", seb->pnum);
printk(KERN_CONT "\n");
}
/*
* In case of unknownerase counter we use the mean erase counter
* value.
*/
ubi_rb_for_each_entry(rb1, sv, &si->volumes, rb) {
ubi_rb_for_each_entry(rb2, seb, &sv->root, u.rb)
if (seb->ec == UBI_SCAN_UNKNOWN_EC)
seb->ec = si->mean_ec;
}
list_for_each_entry(seb, &si->free, u.list) {
if (seb->ec == UBI_SCAN_UNKNOWN_EC)
seb->ec = si->mean_ec;
}
list_for_each_entry(seb, &si->corr, u.list)
if (seb->ec == UBI_SCAN_UNKNOWN_EC)
seb->ec = si->mean_ec;
list_for_each_entry(seb, &si->erase, u.list)
if (seb->ec == UBI_SCAN_UNKNOWN_EC)
seb->ec = si->mean_ec;
err = paranoid_check_si(ubi, si);
if (err) {
if (err > 0)
err = -EINVAL;
goto out_vidh;
}
ubi_free_vid_hdr(ubi, vidh);
kfree(ech);
return si;
out_vidh:
ubi_free_vid_hdr(ubi, vidh);
out_ech:
kfree(ech);
out_si:
ubi_scan_destroy_si(si);
return ERR_PTR(err);
}
1.2． process_ebstatic intprocess_eb(struct ubi_device *ubi, struct ubi_scan_info *si, int pnum)
{
long long uninitialized_var(ec);
int err, bitflips = 0, vol_id, ec_corr = 0;
dbg_bld("scan PEB %d", pnum);
/* Skip bad physical eraseblocks */
err = ubi_io_is_bad(ubi, pnum);
判断一个块是否为坏块，直接调用mtd层的mtd->block_isbad
if (err < 0)
return err;
else if (err) {
/*
* FIXME: this isactually duty of the I/O sub-system to
* initializethis, but MTD does not provide enough
* information.
*/
si->bad_peb_count += 1;
return 0;
}
err = ubi_io_read_ec_hdr(ubi, pnum, ech, 0);//读ec header，一般为一块的第一页
if (err < 0)
return err;
else if (err == UBI_IO_BITFLIPS)
bitflips = 1;
else if (err == UBI_IO_PEB_EMPTY)
return add_to_list(si, pnum, UBI_SCAN_UNKNOWN_EC,&si->erase);
//注意这儿，为什么这个块是empty（也就是全是0xff），还要丢到si->erase队列中呢？这是因为MTD所谓的空与UBI所谓的空不是一回事。在UBI中，空块是指只包含EC头部的块。所以这些需要将全0xff的块进行擦除，写入EC头部
else if (err == UBI_IO_BAD_EC_HDR) {
/*
* We have toalso look at the VID header, possibly it is not
* corrupted. Set%bitflips flag in order to make this PEB be
* moved and ECbe re-created.
*/
ec_corr = 1;
ec = UBI_SCAN_UNKNOWN_EC;
bitflips = 1;
}
si->is_empty = 0;
if (!ec_corr) {
int image_seq;
/* Make sure UBI version is OK */
if (ech->version != UBI_VERSION) {
ubi_err("this UBI version is %d, imageversion is %d",
UBI_VERSION, (int)ech->version);
return -EINVAL;
}
ec = be64_to_cpu(ech->ec);
if (ec > UBI_MAX_ERASECOUNTER) {
/*
* Erasecounter overflow. The EC headers have 64 bits
*reserved, but we anyway make use of only 31 bit
* values,as this seems to be enough for any existing
* flash.Upgrade UBI and use 64-bit erase counters
*internally.
*/
ubi_err("erase counter overflow, max is%d",
ubi_dbg_dump_ec_hdr(ech);
return -EINVAL;
}
/*
* Make sure thatall PEBs have the same image sequence number.
* This allows usto detect situations when users flash UBI
* imagesincorrectly, so that the flash has the new UBI image
* and leftoversfrom the old one. This feature was added
* relativelyrecently, and the sequence number was always
* zero, becauseold UBI implementations always set it to zero.
* For thisreasons, we do not panic if some PEBs have zero
* sequencenumber, while other PEBs have non-zero sequence
* number.
*/
image_seq = be32_to_cpu(ech->image_seq);
if (!ubi->image_seq && image_seq)
ubi->image_seq = image_seq;
if (ubi->image_seq && image_seq &&
ubi->image_seq!= image_seq) {
ubi_err("bad image sequence number %d inPEB %d, "
"expected %d", image_seq, pnum,ubi->image_seq);
ubi_dbg_dump_ec_hdr(ech);
return -EINVAL;
}
}
/* OK, we've done with the EC header, let's look at the VID header*/
err = ubi_io_read_vid_hdr(ubi, pnum, vidh, 0);
if (err < 0)
return err;
else if (err == UBI_IO_BITFLIPS)
bitflips = 1;
else if (err == UBI_IO_BAD_VID_HDR ||
(err == UBI_IO_PEB_FREE && ec_corr)){
//如果是一个块的VID头，那么就添加到corr队列中去
/* VID header is corrupted */
err = add_to_list(si, pnum, ec, &si->corr);
if (err)
return err;
goto adjust_mean_ec;
}else if (err == UBI_IO_PEB_FREE) {
//如果VID头是空的，也就是说该PEB只存在EC头部，那么添加到free队列中，可以用于后面的分配。
/*No VID header - the physical eraseblock is free */
err = add_to_list(si, pnum, ec, &si->free);
if (err)
return err;
goto adjust_mean_ec;
}
vol_id = be32_to_cpu(vidh->vol_id);
if (vol_id > UBI_MAX_VOLUMES && vol_id !=UBI_LAYOUT_VOLUME_ID) {
//判断vol_id是否合法，ubi内部存在一个layout_volume，专门用来保存uservolumn的信息
UBI maintains internalvolumes to store UBI related information e.g. volume information, flash basederase block assignment tables
int lnum = be32_to_cpu(vidh->lnum);
/* Unsupported internal volume */
switch (vidh->compat) {
case UBI_COMPAT_DELETE:
ubi_msg("\"delete\" compatibleinternal volume %d:%d"
" found, remove it", vol_id,lnum);
err = add_to_list(si, pnum, ec,&si->corr);
if (err)
return err;
break;
case UBI_COMPAT_RO:
ubi_msg("read-only compatible internalvolume %d:%d"
" found, switch to read-onlymode",
vol_id, lnum);
ubi->ro_mode = 1;
break;
case UBI_COMPAT_PRESERVE:
ubi_msg("\"preserve\" compatibleinternal volume %d:%d"
" found", vol_id, lnum);
err = add_to_list(si, pnum, ec,&si->alien);
if (err)
return err;
si->alien_peb_count += 1;
return 0;
case UBI_COMPAT_REJECT:
ubi_err("incompatible internal volume %d:%dfound",
vol_id, lnum);
return -EINVAL;
}
}
if (ec_corr)
ubi_warn("valid VID header but corrupted EC headerat PEB %d",
pnum);
//到这儿可以判定这个PEB是一个有效的UBI块，包含有效的EC头部很有效的VID头部
err = ubi_scan_add_used(ubi, si, pnum, ec, vidh, bitflips);
if (err)
return err;
adjust_mean_ec:
if (!ec_corr) {
si->ec_sum += ec;
si->ec_count += 1;
if (ec > si->max_ec)
si->max_ec = ec;
if (ec < si->min_ec)
si->min_ec = ec;
}
return 0;
}
1.3．ubi_scan_add_usedint ubi_scan_add_used (structubi_device *ubi, struct ubi_scan_info *si,int pnum, int ec, const structubi_vid_hdr *vid_hdr,int bitflips)
{
int err, vol_id, lnum;
unsigned long long sqnum;
struct ubi_scan_volume *sv;
struct ubi_scan_leb *seb;
struct rb_node **p, *parent = NULL;
vol_id = be32_to_cpu(vid_hdr->vol_id);
lnum = be32_to_cpu(vid_hdr->lnum);
sqnum = be64_to_cpu(vid_hdr->sqnum);
dbg_bld("PEB %d, LEB %d:%d, EC %d, sqnum %llu, bitflips%d",
pnum, vol_id, lnum, ec, sqnum, bitflips);
sv = add_volume(si, vol_id, pnum, vid_hdr);
调用add_volumn在检查读出的pnum的volumnid号，在内存中建立volumn的红黑树
if (IS_ERR(sv))
return PTR_ERR(sv);
if (si->max_sqnum < sqnum)
si->max_sqnum = sqnum;
/*
* Walk the RB-tree oflogical eraseblocks of volume @vol_id to look
* if this is the firstinstance of this logical eraseblock or not.
*/
p = &sv->root.rb_node;
while (*p) {
int cmp_res;
parent = *p;
seb = rb_entry(parent, struct ubi_scan_leb, u.rb);
if (lnum != seb->lnum) {
if (lnum < seb->lnum)
p = &(*p)->rb_left;
else
p = &(*p)->rb_right;
continue;
}
在内存中建立ubi_scan_leb的红黑树
/*
* There isalready a physical eraseblock describing the same
* logicaleraseblock present.
*/
dbg_bld("this LEB already exists: PEB %d, sqnum%llu, "
"EC %d", seb->pnum, seb->sqnum,seb->ec);
/*
* Make sure thatthe logical eraseblocks have different
* sequencenumbers. Otherwise the image is bad.
*
* However, ifthe sequence number is zero, we assume it must
* be an ancientUBI image from the era when UBI did not have
* sequencenumbers. We still can attach these images, unless
* there is aneed to distinguish between old and new
* eraseblocks,in which case we'll refuse the image in
*'compare_lebs()'. In other words, we attach old clean
* images, butrefuse attaching old images with duplicated
* logicaleraseblocks because there was an unclean reboot.
*/
//注意上面的那个while(1)的范围，到这儿的时候表示在ubi_seb的红黑树中找到了一个描述pnum的ubi_seb结构，那么说明什么问题呢？说明在ubi中存在多个PEB指向同一个LEB.
//sqnum是一个持续增加的64bit的全局变量，我们认为它不会溢出，如果seb->sqnum== sqnum，那么显然是不合理的
if (seb->sqnum == sqnum && sqnum != 0) {
ubi_err("two LEBs with same sequence number%llu",
sqnum);
ubi_dbg_dump_seb(seb, 0);
ubi_dbg_dump_vid_hdr(vid_hdr);
return -EINVAL;
}
/*
* Now we have todrop the older one and preserve the newer
* one.
*/
// * @copy_flag: if this logical eraseblockwas copied from another physical eraseblock (for wear-leveling reasons)
//如果存在多个PEB指向同一个LEB，那么一般是WL的时候，或者修改文件的时候发生了unclean reboot，那么我们就需要从这些多个PEB中找出哪个是最新的。compare_lebs就是完成这个工作的。
cmp_res = compare_lebs(ubi, seb, pnum, vid_hdr);
if (cmp_res < 0)
return cmp_res;
if (cmp_res & 1) {
/*
* Thislogical eraseblock is newer then the one
* foundearlier.
*/
err = validate_vid_hdr(vid_hdr, sv, pnum);
if (err)
return err;
if (cmp_res & 4)
err = add_to_list(si, seb->pnum,seb->ec,
&si->corr);
else
err = add_to_list(si, seb->pnum, seb->ec,
&si->erase);
if (err)
return err;
seb->ec = ec;
seb->pnum = pnum;
seb->scrub = ((cmp_res & 2) || bitflips);
seb->sqnum = sqnum;
if (sv->highest_lnum == lnum)
sv->last_data_size =
be32_to_cpu(vid_hdr->data_size);
return 0;
/*
* Thislogical eraseblock is older than the one found
*previously.
*/
if (cmp_res & 4)
return add_to_list(si, pnum, ec,&si->corr);
else
return add_to_list(si, pnum, ec,&si->erase);
}
}
/*
* We've met thislogical eraseblock for the first time, add it to the
* scanning information.
*/
//如果到这儿了，表示这是第一次遇到该LEB，那么很简单，将它添加到队列中就可以了
err = validate_vid_hdr(vid_hdr, sv, pnum);
if (err)
return err;
seb = kmalloc(sizeof(struct ubi_scan_leb), GFP_KERNEL);
if (!seb)
return -ENOMEM;
seb->ec = ec;
seb->pnum = pnum;
seb->lnum = lnum;
seb->sqnum = sqnum;
seb->scrub = bitflips;
if (sv->highest_lnum <= lnum) {
sv->highest_lnum = lnum;
sv->last_data_size =be32_to_cpu(vid_hdr->data_size);
}
sv->leb_count += 1;
rb_link_node(&seb->u.rb, parent, p);
rb_insert_color(&seb->u.rb, &sv->root);
return 0;
}
1.4．compare_lebs
static intcompare_lebs(struct ubi_device *ubi, const struct ubi_scan_leb *seb,int pnum,const struct ubi_vid_hdr *vid_hdr)
{
void *buf;
int len, err, second_is_newer, bitflips = 0, corrupted = 0;
uint32_t data_crc, crc;
struct ubi_vid_hdr *vh = NULL;
unsigned long long sqnum2 = be64_to_cpu(vid_hdr->sqnum);
//再次判断一下是否存在sqnum相等的情况发生
if (sqnum2 == seb->sqnum) {
/*
* This must be areally ancient UBI image which has been
* created beforesequence numbers support has been added. At
* that times weused 32-bit LEB versions stored in logical
* eraseblocks.That was before UBI got into mainline. We do not
* support theseimages anymore. Well, those images will work
* still work,but only if no unclean reboots happened.
*/
ubi_err("unsupported on-flash UBI format\n");
return -EINVAL;
}
/* Obviously the LEB with lower sequence counter is older */
//因为sqnum是持续增加的，而且不会溢出。所以认为sqnum大的那个PEB是最新的。 second_is_newer= !!(sqnum2 > seb->sqnum);
/*
* Now we know whichcopy is newer. If the copy flag of the PEB with
* newer version is notset, then we just return, otherwise we have to
* check data CRC. Forthe second PEB we already have the VID header,
* for the first one -we'll need to re-read it from flash.
*
* Note: this may beoptimized so that we wouldn't read twice.
*/
if (second_is_newer) {
if (!vid_hdr->copy_flag) {
/*It is not a copy, so it is newer */
dbg_bld("second PEB %d is newer, copy_flagis unset",
pnum);
return 1;
}
} else {
//如果copy_flag位设置了，那么可以认为是在WL的时候发生意外。因为发生了unclear reboot，所以需要判断这个最新的PEB中的数据是否是完整的。（unclean reboot时数据可能被打断了）
pnum =seb->pnum;
vh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
if (!vh)
return -ENOMEM;
err = ubi_io_read_vid_hdr(ubi, pnum, vh, 0);
if (err) {
if (err == UBI_IO_BITFLIPS)
bitflips = 1;
else {
dbg_err("VID of PEB %d header isbad, but it "
"was OK earlier", pnum);
if (err > 0)
err = -EIO;
goto out_free_vidh;
}
}
if (!vh->copy_flag) {
/*It is not a copy, so it is newer */
dbg_bld("first PEB %d is newer, copy_flagis unset",
pnum);
err = bitflips << 1;
goto out_free_vidh;
}
vid_hdr = vh;
}
/* Read the data of the copy and check the CRC */
len = be32_to_cpu(vid_hdr->data_size);
buf = vmalloc(len);
if (!buf) {
err = -ENOMEM;
goto out_free_vidh;
}
//OK,读出数据，校验CRC
err = ubi_io_read_data(ubi, buf, pnum, 0, len);
if (err && err != UBI_IO_BITFLIPS && err !=-EBADMSG)
goto out_free_buf;
data_crc = be32_to_cpu(vid_hdr->data_crc);
crc = crc32(UBI_CRC32_INIT, buf, len);
if (crc != data_crc) {
dbg_bld("PEB %d CRC error: calculated %#08x, mustbe %#08x",
pnum, crc, data_crc);
corrupted = 1;
bitflips = 0;
//如果CRC校验失败了，那么还沿用老的PEB
second_is_newer = !second_is_newer;
dbg_bld("PEB %d CRC is OK", pnum);
bitflips = !!err;
}
vfree(buf);
ubi_free_vid_hdr(ubi, vh);
if (second_is_newer)
dbg_bld("second PEB %d is newer, copy_flag isset", pnum);
else
dbg_bld("first PEB %d is newer, copy_flag isset", pnum);
return second_is_newer | (bitflips << 1) | (corrupted<< 2);
out_free_buf:
vfree(buf);
out_free_vidh:
ubi_free_vid_hdr(ubi, vh);
return err;
}
二．创建volume
ubimkvol /dev/ubi0 -N ubifs -s 15MiB
上面的这条命令是在ubi设备0上创建一个大小为15M，名字叫做ubifs的volumn
这条命令是通过ioctl实现的，我们下面来看一下相关的代码：
/*Create volume command */
caseUBI_IOCMKVOL:
{
structubi_mkvol_req req;
dbg_gen("createvolume");
err= copy_from_user(&req, argp, sizeof(struct ubi_mkvol_req));
if(err) {
err= -EFAULT;
break;
}
req.name[req.name_len]= '\0';
err= verify_mkvol_req(ubi, &req);
if(err)
break;
mutex_lock(&ubi->device_mutex);
err= ubi_create_volume(ubi, &req);
mutex_unlock(&ubi->device_mutex);
if(err)
break;
err= put_user(req.vol_id, (__user int32_t *)argp);
if(err)
err= -EFAULT;
break;
}
函数的主体部分是ubi_create_volume。传给ubi_create_volume的是一个ubi_mkvol_req类型的结构体。
struct ubi_mkvol_req {
__s32 vol_id;//要创建的volumn的ID，可以不指定
__s32 alignment;//The @alignment field specifies the requiredalignment of the volume logical eraseblock. This means, that the size oflogical eraseblocks will be aligned to this number, i.e.,
(UBI device logicaleraseblock size) mod (@alignment) = 0.
__s64 bytes;//volume的大小
__s8 vol_type;//volume的类型，静态或者动态
__s8 padding1;
__s16 name_len;//volume的名字的长度
__s8 padding2[4];
char name[UBI_MAX_VOLUME_NAME + 1];
} __attribute__((packed));
intubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
{
int i, err, vol_id = req->vol_id, do_free = 1;
struct ubi_volume *vol;
struct ubi_vtbl_record vtbl_rec;
dev_t dev;
if (ubi->ro_mode)
return -EROFS;
vol = kzalloc(sizeof(struct ubi_volume), GFP_KERNEL);
if (!vol)
return -ENOMEM;
spin_lock(&ubi->volumes_lock);
//如果没有指定vol-id,那么就是采用默认的方式获得id
if (vol_id == UBI_VOL_NUM_AUTO) {
/* Find unused volume ID */
dbg_gen("search for vacant volume ID");
for (i = 0; i < ubi->vtbl_slots; i++)
if (!ubi->volumes[i]) {
vol_id = i;
break;
}
if (vol_id == UBI_VOL_NUM_AUTO) {
dbg_err("out of volume IDs");
err = -ENFILE;
goto out_unlock;
}
req->vol_id = vol_id;
}
dbg_gen("create device %d, volume %d, %llu bytes, type%d, name %s",
ubi->ubi_num, vol_id, (unsigned longlong)req->bytes,
(int)req->vol_type, req->name);
/* Ensure that this volume does not exist */
err = -EEXIST;
if (ubi->volumes[vol_id]) {
dbg_err("volume %d already exists", vol_id);
goto out_unlock;
}
/* Ensure that the name is unique */
//确认要创建的volume的名字是唯一的。与已经存在的volume对比
for (i = 0; i < ubi->vtbl_slots; i++)
if (ubi->volumes[i] &&
ubi->volumes[i]->name_len == req->name_len &&
!strcmp(ubi->volumes[i]->name,req->name)) {
dbg_err("volume \"%s\" exists (ID%d)", req->name, i);
goto out_unlock;
}
//根据req->bytes计算需要的物理块数，UBI中操作的基本单元是物理块
/*Calculate how many eraseblocks are requested */
vol->usable_leb_size = ubi->leb_size - ubi->leb_size% req->alignment;
vol->reserved_pebs += div_u64(req->bytes +vol->usable_leb_size - 1,
vol->usable_leb_size);
/* Reserve physical eraseblocks */
if (vol->reserved_pebs > ubi->avail_pebs) {
dbg_err("not enough PEBs, only %d available",ubi->avail_pebs);
err = -ENOSPC;
goto out_unlock;
}
//将ubi设备中的可用pebs减少，因为已经分配了新创建的volume
ubi->avail_pebs -= vol->reserved_pebs;
ubi->rsvd_pebs += vol->reserved_pebs;
spin_unlock(&ubi->volumes_lock);
//初始化新创建的volume的相关信息
vol->vol_id =vol_id;
vol->alignment = req->alignment;
vol->data_pad =ubi->leb_size % vol->alignment;
vol->vol_type =req->vol_type;
vol->name_len =req->name_len;
memcpy(vol->name, req->name, vol->name_len);
vol->ubi = ubi;
/*
* Finish all pendingerases because there may be some LEBs belonging
* to the same volumeID.
*/
//刷新UBI后台中pending的workers。
err = ubi_wl_flush(ubi);
if (err)
goto out_acc;
//创建eba_tbl表，并将其初始化为UBI_LEB_UNMAPPED，只有在对具体的LEB进行写操作的时候才会真正的更新该表中的每一个LEB对应的项
vol->eba_tbl = kmalloc(vol->reserved_pebs * sizeof(int),GFP_KERNEL);
if (!vol->eba_tbl) {
err = -ENOMEM;
goto out_acc;
}
for (i = 0; i < vol->reserved_pebs; i++)
vol->eba_tbl[i] = UBI_LEB_UNMAPPED;
if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
vol->used_ebs = vol->reserved_pebs;
vol->last_eb_bytes = vol->usable_leb_size;
vol->used_bytes =
(long long)vol->used_ebs *vol->usable_leb_size;
vol->used_ebs = div_u64_rem(vol->used_bytes,
vol->usable_leb_size,
&vol->last_eb_bytes);
if (vol->last_eb_bytes != 0)
vol->used_ebs += 1;
else
vol->last_eb_bytes = vol->usable_leb_size;
}
/* Register character device for the volume */
//给ubivolume注册字符接口
cdev_init(&vol->cdev, &ubi_vol_cdev_operations);
vol->cdev.owner = THIS_MODULE;
dev = MKDEV(MAJOR(ubi->cdev.dev), vol_id + 1);
err = cdev_add(&vol->cdev, dev, 1);
if (err) {
ubi_err("cannot add character device");
goto out_mapping;
}
vol->dev.release = vol_release;
vol->dev.parent = &ubi->dev;
vol->dev.devt = dev;
vol->dev.class = ubi_class;
dev_set_name(&vol->dev, "%s_%d",ubi->ubi_name, vol->vol_id);
err = device_register(&vol->dev);
if (err) {
ubi_err("cannot register device");
goto out_cdev;
}
err = volume_sysfs_init(ubi, vol);
if (err)
goto out_sysfs;
/* Fill volume table record */
//ubi中存在一个internalvolume ，其中保持的是每一个volume 的信息，现在新创建了一个volume，就需要更新其中的这个internal volume（layout volume）的信息
memset(&vtbl_rec, 0, sizeof(struct ubi_vtbl_record));
vtbl_rec.reserved_pebs = cpu_to_be32(vol->reserved_pebs);
vtbl_rec.alignment =cpu_to_be32(vol->alignment);
vtbl_rec.data_pad =cpu_to_be32(vol->data_pad);
vtbl_rec.name_len =cpu_to_be16(vol->name_len);
if (vol->vol_type == UBI_DYNAMIC_VOLUME)
vtbl_rec.vol_type = UBI_VID_DYNAMIC;
else
vtbl_rec.vol_type = UBI_VID_STATIC;
memcpy(vtbl_rec.name, vol->name, vol->name_len);
err = ubi_change_vtbl_record(ubi, vol_id, &vtbl_rec);
通过一个ubi_eba_unmap_leb操作，和一个ubi_eba_write_leb操作来实现了ubifs的写操作，保证了数据的安全性
if (err)
goto out_sysfs;
spin_lock(&ubi->volumes_lock);
ubi->volumes[vol_id] = vol;
ubi->vol_count += 1;
spin_unlock(&ubi->volumes_lock);
//通知相关模块，UBI创建了一个新的volume，让它们也采取相应的措施，貌似这个通知联上只有gluebi_notifier。
ubi_volume_notify(ubi, vol, UBI_VOLUME_ADDED);
if (paranoid_check_volumes(ubi))
dbg_err("check failed while creating volume%d", vol_id);
return err;
out_sysfs:
/*
* We have registeredour device, we should not free the volume
* description object inthis function in case of an error - it is
* freed by the releasefunction.
*
* Get device referenceto prevent the release function from being
* called just aftersysfs has been closed.
*/
do_free = 0;
get_device(&vol->dev);
volume_sysfs_close(vol);
out_cdev:
cdev_del(&vol->cdev);
out_mapping:
if (do_free)
kfree(vol->eba_tbl);
out_acc:
spin_lock(&ubi->volumes_lock);
ubi->rsvd_pebs -= vol->reserved_pebs;
ubi->avail_pebs += vol->reserved_pebs;
out_unlock:
spin_unlock(&ubi->volumes_lock);
if (do_free)
kfree(vol);
else
put_device(&vol->dev);
ubi_err("cannot create volume %d, error %d", vol_id,err);
return err;
}
三．Mount过程
static int mount_ubifs(struct ubifs_info *c)
static int mount_ubifs(struct ubifs_info *c)
{
struct super_block *sb= c->vfs_sb;
int err,mounted_read_only = (sb->s_flags & MS_RDONLY);
long long x;
size_t sz;
err =init_constants_early(c);
if (err)
return err;
err =ubifs_debugging_init(c);
if (err)
return err;
//通过检查vtl表来确定volume是否为空
err =check_volume_empty(c);
if (err)
goto out_free;
//如果该volume为空，但是只读的话，显然不能写入信息，自然
//也就不能mount了
if (c->empty&& (mounted_read_only || c->ro_media)) {
/*
* This UBI volume is empty, and read-only, orthe file system
* is mounted read-only - we cannot format it.
*/
ubifs_err("can'tformat empty UBI volume: read-only %s",
c->ro_media ? "UBI volume" :"mount");
err = -EROFS;
goto out_free;
}
if (c->ro_media&& !mounted_read_only) {
ubifs_err("cannotmount read-write - read-only media");
err = -EROFS;
goto out_free;
}
/*
* The requirement for the buffer is that itshould fit indexing B-tree
* height amount of integers. We assume theheight if the TNC tree will
* never exceed 64.
*/
err = -ENOMEM;
//bottom_up_buf: a buffer which isused by 'dirty_cow_bottom_up()' in tnc.c,在后面我们会看到在dirty_cow_bottom_up中将znode的所有的ancestors（父节点，父节点的父节点，一直到根节点未知）都设为dirty。所以在标记之前要记录一下所以的ancestors znode。这个bottom_up_buf就是用于这个目的的。
c->bottom_up_buf =kmalloc(BOTTOM_UP_HEIGHT * sizeof(int), GFP_KERNEL);
if(!c->bottom_up_buf)
goto out_free;
//sbuf: LEB-sizedbuffer to use
c->sbuf =vmalloc(c->leb_size);
if (!c->sbuf)
goto out_free;
if(!mounted_read_only) {
//@ileb_buf:buffer for commit in-the-gaps method
c->ileb_buf= vmalloc(c->leb_size);
if(!c->ileb_buf)
gotoout_free;
}
if (c->bulk_read ==1)
//初始化bulk-read的信息，关于bulk-read的相关信息可以在通过VFS的读操作中看到详细的解释
bu_init(c);
/*
* We have to check all CRCs, even for datanodes, when we mount the FS
* (specifically, when we are replaying).
*/
c->always_chk_crc =1;
//读超级块，如果该volume是空的，显然不存在超级块，这时候需要创建一个最初的文件系统
err =ubifs_read_superblock(c);
if (err)
goto out_free;
/*
* Make sure the compressor which is set asdefault in the superblock
* or overridden by mount options is actuallycompiled in.
*/
if(!ubifs_compr_present(c->default_compr)) {
ubifs_err("'compressor\"%s\" is not compiled in",
ubifs_compr_name(c->default_compr));
err =-ENOTSUPP;
goto out_free;
}
//初始化ubifs的一些常量
err =init_constants_sb(c);
if (err)
goto out_free;
sz =ALIGN(c->max_idx_node_sz, c->min_io_size);
sz = ALIGN(sz +c->max_idx_node_sz, c->min_io_size);
c->cbuf =kmalloc(sz, GFP_NOFS);
if (!c->cbuf) {
err = -ENOMEM;
goto out_free;
}
sprintf(c->bgt_name,BGT_NAME_PATTERN, c->vi.ubi_num, c->vi.vol_id);
if(!mounted_read_only) {
err = alloc_wbufs(c);
if (err)
gotoout_cbuf;
/* Createbackground thread */
//创建UBIFS的后台进程，这个后台进程主要用于基于wbuf的读写
c->bgt =kthread_create(ubifs_bg_thread, c, "%s", c->bgt_name);
if(IS_ERR(c->bgt)) {
err =PTR_ERR(c->bgt);
c->bgt= NULL;
ubifs_err("cannotspawn \"%s\", error %d",
c->bgt_name, err);
gotoout_wbufs;
}
//唤醒该进程
wake_up_process(c->bgt);
}
err = ubifs_read_master(c);
//见下面的具体描述
if (err)
goto out_free;
/*
* Make sure the compressor which is set asdefault in the superblock
* or overridden by mount options is actuallycompiled in.
*/
if(!ubifs_compr_present(c->default_compr)) {
ubifs_err("'compressor\"%s\" is not compiled in",
ubifs_compr_name(c->default_compr));
err =-ENOTSUPP;
goto out_free;
}
err =init_constants_sb(c);
if (err)
goto out_free;
sz = ALIGN(c->max_idx_node_sz,c->min_io_size);
sz = ALIGN(sz +c->max_idx_node_sz, c->min_io_size);
c->cbuf =kmalloc(sz, GFP_NOFS);
if (!c->cbuf) {
err = -ENOMEM;
goto out_free;
}
sprintf(c->bgt_name,BGT_NAME_PATTERN, c->vi.ubi_num, c->vi.vol_id);
if (!mounted_read_only){
err =alloc_wbufs(c);
if (err)
gotoout_cbuf;
/* Createbackground thread */
c->bgt =kthread_create(ubifs_bg_thread, c, "%s", c->bgt_name);
if(IS_ERR(c->bgt)) {
err =PTR_ERR(c->bgt);
c->bgt= NULL;
ubifs_err("cannotspawn \"%s\", error %d",
c->bgt_name, err);
gotoout_wbufs;
}
wake_up_process(c->bgt);
}
err =ubifs_read_master(c);
if (err)
gotoout_master;
init_constants_master(c);
if((c->mst_node->flags & cpu_to_le32(UBIFS_MST_DIRTY)) != 0) {
ubifs_msg("recoveryneeded");
c->need_recovery= 1;
if(!mounted_read_only) {
err =ubifs_recover_inl_heads(c, c->sbuf);
if (err)
gotoout_master;
}
} else if(!mounted_read_only) {
/*
* Set the "dirty" flag so that if wereboot uncleanly we
* will notice this immediately on the nextmount.
*/
c->mst_node->flags|= cpu_to_le32(UBIFS_MST_DIRTY);
err =ubifs_write_master(c);
if (err)
gotoout_master;
}
err =ubifs_lpt_init(c, 1, !mounted_read_only);
if (err)
goto out_lpt;
err =dbg_check_idx_size(c, c->old_idx_sz);
if (err)
goto out_lpt;
err =ubifs_replay_journal(c);
if (err)
gotoout_journal;
/* Calculate'min_idx_lebs' after journal replay */
c->min_idx_lebs =ubifs_calc_min_idx_lebs(c);
err = ubifs_mount_orphans(c,c->need_recovery, mounted_read_only);
if (err)
gotoout_orphans;
if(!mounted_read_only) {
int lnum;
err =check_free_space(c);
if (err)
gotoout_orphans;
/* Check forenough log space */
lnum =c->lhead_lnum + 1;
if (lnum >=UBIFS_LOG_LNUM + c->log_lebs)
lnum =UBIFS_LOG_LNUM;
if (lnum ==c->ltail_lnum) {
err =ubifs_consolidate_log(c);
if (err)
gotoout_orphans;
}
if(c->need_recovery) {
err =ubifs_recover_size(c);
if (err)
gotoout_orphans;
err =ubifs_rcvry_gc_commit(c);
err =take_gc_lnum(c);
if (err)
gotoout_orphans;
/*
* GC LEB may contain garbage if there was anunclean
* reboot, and it should be un-mapped.
*/
err =ubifs_leb_unmap(c, c->gc_lnum);
if (err)
returnerr;
}
err =dbg_check_lprops(c);
if (err)
gotoout_orphans;
err =ubifs_recover_size(c);
if (err)
gotoout_orphans;
/*
* Even if we mount read-only, we have to setspace in GC LEB
* to proper value because this affects UBIFSfree space
* reporting. We do not want to have asituation when
* re-mounting from R/O to R/W changes amountof free space.
*/
err =take_gc_lnum(c);
if (err)
goto out_orphans;
}
spin_lock(&ubifs_infos_lock);
list_add_tail(&c->infos_list,&ubifs_infos);
spin_unlock(&ubifs_infos_lock);
if(c->need_recovery) {
if(mounted_read_only)
ubifs_msg("recoverydeferred");
else {
c->need_recovery= 0;
ubifs_msg("recoverycompleted");
/*
* GC LEB has to be empty and taken at thispoint. But
* the journal head LEBs may also be accountedas
* "empty taken" if they are empty.
*/
ubifs_assert(c->lst.taken_empty_lebs> 0);
}
} else
ubifs_assert(c->lst.taken_empty_lebs> 0);
err =dbg_check_filesystem(c);
if (err)
goto out_infos;
err =dbg_debugfs_init_fs(c);
if (err)
goto out_infos;
c->always_chk_crc =0;
ubifs_msg("mountedUBI device %d, volume %d, name \"%s\"",
c->vi.ubi_num, c->vi.vol_id,c->vi.name);
if (mounted_read_only)
ubifs_msg("mountedread-only");
x = (longlong)c->main_lebs * c->leb_size;
ubifs_msg("filesystem size: %lld bytes (%lld KiB, %lldMiB, %d "
"LEBs)", x, x >> 10, x>> 20, c->main_lebs);
x = (longlong)c->log_lebs * c->leb_size + c->max_bud_bytes;
ubifs_msg("journalsize: %lld bytes (%lld KiB, %lldMiB, %d "
"LEBs)", x, x >> 10, x>> 20, c->log_lebs + c->max_bud_cnt);
ubifs_msg("mediaformat: w%d/r%d (latest isw%d/r%d)",
c->fmt_version, c->ro_compat_version,
UBIFS_FORMAT_VERSION,UBIFS_RO_COMPAT_VERSION);
ubifs_msg("defaultcompressor: %s", ubifs_compr_name(c->default_compr));
ubifs_msg("reservedfor root: %llu bytes (%llu KiB)",
c->report_rp_size,c->report_rp_size >> 10);
dbg_msg("compiledon: " __DATE__ " at" __TIME__);
dbg_msg("min. I/Ounit size: %d bytes",c->min_io_size);
dbg_msg("LEBsize: %d bytes (%d KiB)",
c->leb_size,c->leb_size >> 10);
dbg_msg("datajournal heads: %d",
c->jhead_cnt- NONDATA_JHEADS_CNT);
dbg_msg("UUID: %02X%02X%02X%02X-%02X%02X"
"-%02X%02X-%02X%02X-%02X%02X%02X%02X%02X%02X",
c->uuid[0], c->uuid[1],c->uuid[2], c->uuid[3],
c->uuid[4], c->uuid[5],c->uuid[6], c->uuid[7],
c->uuid[8], c->uuid[9],c->uuid[10], c->uuid[11],
c->uuid[12], c->uuid[13],c->uuid[14], c->uuid[15]);
dbg_msg("big_lpt %d", c->big_lpt);
dbg_msg("logLEBs: %d (%d - %d)",
c->log_lebs,UBIFS_LOG_LNUM, c->log_last);
dbg_msg("LPT areaLEBs: %d (%d - %d)",
c->lpt_lebs,c->lpt_first, c->lpt_last);
dbg_msg("orphanarea LEBs: %d (%d - %d)",
c->orph_lebs,c->orph_first, c->orph_last);
dbg_msg("mainarea LEBs: %d (%d - %d)",
c->main_lebs,c->main_first, c->leb_cnt - 1);
dbg_msg("indexLEBs: %d",c->lst.idx_lebs);
dbg_msg("totalindex bytes: %lld (%lld KiB, %lldMiB)",
c->old_idx_sz,c->old_idx_sz >> 10, c->old_idx_sz >> 20);
dbg_msg("key hashtype: %d",c->key_hash_type);
dbg_msg("treefanout: %d", c->fanout);
dbg_msg("reservedGC LEB: %d", c->gc_lnum);
dbg_msg("firstmain LEB: %d",c->main_first);
dbg_msg("max.znode size %d",c->max_znode_sz);
dbg_msg("max.index node size %d", c->max_idx_node_sz);
dbg_msg("nodesizes: data %zu, inode %zu,dentry %zu",
UBIFS_DATA_NODE_SZ,UBIFS_INO_NODE_SZ, UBIFS_DENT_NODE_SZ);
dbg_msg("nodesizes: trun %zu, sb %zu, master%zu",
UBIFS_TRUN_NODE_SZ,UBIFS_SB_NODE_SZ, UBIFS_MST_NODE_SZ);
dbg_msg("nodesizes: ref %zu, cmt. start %zu,orph %zu",
UBIFS_REF_NODE_SZ,UBIFS_CS_NODE_SZ, UBIFS_ORPH_NODE_SZ);
dbg_msg("max.node sizes: data %zu, inode %zudentry %zu",
UBIFS_MAX_DATA_NODE_SZ,UBIFS_MAX_INO_NODE_SZ,
dbg_msg("deadwatermark: %d", c->dead_wm);
dbg_msg("darkwatermark: %d", c->dark_wm);
dbg_msg("LEBoverhead: %d",c->leb_overhead);
x = (longlong)c->main_lebs * c->dark_wm;
dbg_msg("max.dark space: %lld (%lld KiB, %lldMiB)",
x, x >>10, x >> 20);
dbg_msg("maximumbud bytes: %lld (%lld KiB, %lldMiB)",
c->max_bud_bytes,c->max_bud_bytes >> 10,
c->max_bud_bytes>> 20);
dbg_msg("BGcommit bud bytes: %lld (%lld KiB, %lld MiB)",
c->bg_bud_bytes,c->bg_bud_bytes >> 10,
c->bg_bud_bytes>> 20);
dbg_msg("currentbud bytes %lld (%lld KiB, %lldMiB)",
c->bud_bytes,c->bud_bytes >> 10, c->bud_bytes >> 20);
dbg_msg("max.seq. number: %llu",c->max_sqnum);
dbg_msg("commitnumber: %llu", c->cmt_no);
return 0;
out_infos:
spin_lock(&ubifs_infos_lock);
list_del(&c->infos_list);
spin_unlock(&ubifs_infos_lock);
out_orphans:
free_orphans(c);
out_journal:
destroy_journal(c);
out_lpt:
ubifs_lpt_free(c, 0);
out_master:
kfree(c->mst_node);
kfree(c->rcvrd_mst_node);
if (c->bgt)
kthread_stop(c->bgt);
out_wbufs:
free_wbufs(c);
out_cbuf:
kfree(c->cbuf);
out_free:
kfree(c->bu.buf);
vfree(c->ileb_buf);
vfree(c->sbuf);
kfree(c->bottom_up_buf);
ubifs_debugging_exit(c);
return err;
}
3.1 ubifs_read_superblock
int ubifs_read_superblock(struct ubifs_info *c)
{
int err, sup_flags;
struct ubifs_sb_node*sup;
//如果前面扫描的时候发现该卷中的LEB全部没有map，因此是一个空卷，什么信息都没有，这时候需要建立一个最原始的文件系统，其实就是写入superblock节点（LEB0），master节点（LEB1，和LEB2），commit节点（LEB3），inode节点（main_first+1），index节点（main_first+0）。
//对于这些节点，我觉得很有必要详细的描述一下。我们都知道每一个文件系统都有一个超级块，里面存放的是文件系统的基本信息，在这儿ubifs将超级块以superblock类型节点的形式写进了flash media。
//从《a brief introduce of ubi and ubifs》的文档中可以看出。为了垃圾回收，采用node-structure的形式组织文件，jiffs2中这些相关的数据结构是在mount的时候建立的，这样花费了大量的时间和内存资源，而ubifs中这些数据是保存在flash media中的。Master节点就是这样的树状信息的根节点。Master节点是一式两份的，分别保存在LEB1和LEB2上。为什么需要两份呢？
因为文件更新的时候，B+tree中的数据会变的，相应的master也就需要更新，为了防止在更新master的时候发生unclean reboot导致数据被破坏，所以保存了两份，用于unclean reboot时候的数据恢复。
if (c->empty) {
err =create_default_filesystem(c);
if (err)
returnerr;
}
//读出超级块，当然这个超级块有可能是上面的create_default_filesystem刚刚写进去的。
sup =ubifs_read_sb_node(c);
if (IS_ERR(sup))
returnPTR_ERR(sup);
c->fmt_version =le32_to_cpu(sup->fmt_version);
c->ro_compat_version= le32_to_cpu(sup->ro_compat_version);
/*
* The software supports all previous versionsbut not future versions,
* due to the unavailability of time-travellingequipment.
*/
if (c->fmt_version> UBIFS_FORMAT_VERSION) {
structsuper_block *sb = c->vfs_sb;
int mounting_ro= sb->s_flags & MS_RDONLY;
ubifs_assert(!c->ro_media|| mounting_ro);
if(!mounting_ro ||
c->ro_compat_version >UBIFS_RO_COMPAT_VERSION) {
ubifs_err("on-flashformat version is w%d/r%d, but "
"software only supports up to version "
"w%d/r%d", c->fmt_version,
c->ro_compat_version,UBIFS_FORMAT_VERSION,
UBIFS_RO_COMPAT_VERSION);
if(c->ro_compat_version <= UBIFS_RO_COMPAT_VERSION) {
ubifs_msg("onlyR/O mounting is possible");
err= -EROFS;
} else
err= -EINVAL;
gotoout;
}
/*
* The FS is mounted R/O, and the media formatis
* R/O-compatible with the UBIFSimplementation, so we can
* mount.
*/
c->rw_incompat= 1;
}
if (c->fmt_version< 3) {
ubifs_err("on-flashformat version %d is not supported",
c->fmt_version);
err = -EINVAL;
goto out;
}
//采用哪种hash运算方法
switch (sup->key_hash) {
caseUBIFS_KEY_HASH_R5:
c->key_hash= key_r5_hash;
c->key_hash_type= UBIFS_KEY_HASH_R5;
break;
caseUBIFS_KEY_HASH_TEST:
c->key_hash= key_test_hash;
c->key_hash_type= UBIFS_KEY_HASH_TEST;
break;
};
c->key_fmt =sup->key_fmt;
switch (c->key_fmt){
caseUBIFS_SIMPLE_KEY_FMT:
c->key_len =UBIFS_SK_LEN;
break;
default:
ubifs_err("unsupportedkey format");
err = -EINVAL;
goto out;
}
//用从超级块中读出的信息来初始化内存中的ubifs_info结构体
c->leb_cnt = le32_to_cpu(sup->leb_cnt);
c->max_leb_cnt = le32_to_cpu(sup->max_leb_cnt);
c->max_bud_bytes =le64_to_cpu(sup->max_bud_bytes);
c->log_lebs = le32_to_cpu(sup->log_lebs);
c->lpt_lebs = le32_to_cpu(sup->lpt_lebs);
c->orph_lebs = le32_to_cpu(sup->orph_lebs);
c->jhead_cnt = le32_to_cpu(sup->jhead_cnt) +NONDATA_JHEADS_CNT;
c->fanout = le32_to_cpu(sup->fanout);
c->lsave_cnt = le32_to_cpu(sup->lsave_cnt);
c->rp_size = le64_to_cpu(sup->rp_size);
c->rp_uid = le32_to_cpu(sup->rp_uid);
c->rp_gid = le32_to_cpu(sup->rp_gid);
sup_flags = le32_to_cpu(sup->flags);
if(!c->mount_opts.override_compr)
c->default_compr= le16_to_cpu(sup->default_compr);
c->vfs_sb->s_time_gran= le32_to_cpu(sup->time_gran);
memcpy(&c->uuid,&sup->uuid, 16);
c->big_lpt =!!(sup_flags & UBIFS_FLG_BIGLPT);
/* Automaticallyincrease file system size to the maximum size */
//ubi的volume是可以resize的，即可以改变大小。此时需要重新写超级块
c->old_leb_cnt =c->leb_cnt;
if (c->leb_cnt <c->vi.size && c->leb_cnt < c->max_leb_cnt) {
c->leb_cnt =min_t(int, c->max_leb_cnt, c->vi.size);
if(c->vfs_sb->s_flags & MS_RDONLY)
dbg_mnt("Autoresizing (ro) from %d LEBs to %d LEBs",
c->old_leb_cnt, c->leb_cnt);
else {
dbg_mnt("Autoresizing (sb) from %d LEBs to %d LEBs",
c->old_leb_cnt,c->leb_cnt);
sup->leb_cnt= cpu_to_le32(c->leb_cnt);
err =ubifs_write_sb_node(c, sup);
if (err)
gotoout;
c->old_leb_cnt= c->leb_cnt;
}
}
c->log_bytes =(long long)c->log_lebs * c->leb_size;
c->log_last =UBIFS_LOG_LNUM + c->log_lebs - 1;
c->lpt_first =UBIFS_LOG_LNUM + c->log_lebs;
c->lpt_last =c->lpt_first + c->lpt_lebs - 1;
c->orph_first =c->lpt_last + 1;
c->orph_last =c->orph_first + c->orph_lebs - 1;
c->main_lebs =c->leb_cnt - UBIFS_SB_LEBS - UBIFS_MST_LEBS;
c->main_lebs -=c->log_lebs + c->lpt_lebs + c->orph_lebs;
c->main_first =c->leb_cnt - c->main_lebs;
err = validate_sb(c,sup);
out:
kfree(sup);
return err;
}
3.2create_default_filesystem
static int create_default_filesystem(struct ubifs_info *c)
{
struct ubifs_sb_node*sup;
struct ubifs_mst_node*mst;
struct ubifs_idx_node*idx;
struct ubifs_branch*br;
struct ubifs_ino_node*ino;
struct ubifs_cs_node*cs;
union ubifs_key key;
int err, tmp,jnl_lebs, log_lebs, max_buds, main_lebs, main_first;
int lpt_lebs,lpt_first, orph_lebs, big_lpt, ino_waste, sup_flags = 0;
int min_leb_cnt =UBIFS_MIN_LEB_CNT;
long long tmp64,main_bytes;
__le64 tmp_le64;
/* Some functionscalled from here depend on the @c->key_len filed */
c->key_len =UBIFS_SK_LEN;
/*
* First of all, we have to calculate defaultfile-system geometry -
* log size, journal size, etc.
*/
//首先根据文件系统的大小算相应的journal和log区的大小。Journal的目的前面可能已经提到了，因为ubifs的文件的B+tree的数据是保存在flash media中，这就带来了一个问题，每次更新文件的时候都需要更新相关的B+tree的信息，这样就会频繁的读写flash设备，降低文件系统的性能。所以采用了joural，也就是说在更新的时候先将更新相关inode的信息写进log中，在log满了的时候才一起更新flash media中的B+tree。这样降低了更新的频率，提高了文件系统的性能。
if (c->leb_cnt <0x7FFFFFFF / DEFAULT_JNL_PERCENT)
/* We can firstmultiply then divide and have no overflow */
jnl_lebs =c->leb_cnt * DEFAULT_JNL_PERCENT / 100;
else
jnl_lebs =(c->leb_cnt / 100) * DEFAULT_JNL_PERCENT;
if (jnl_lebs <UBIFS_MIN_JNL_LEBS)
jnl_lebs =UBIFS_MIN_JNL_LEBS;
if (jnl_lebs *c->leb_size > DEFAULT_MAX_JNL)
jnl_lebs =DEFAULT_MAX_JNL / c->leb_size;
/*
* The log should be large enough to fitreference nodes for all bud
* LEBs. Because buds do not have to start fromthe beginning of LEBs
* (half of the LEB may contain committeddata), the log should
* generally be larger, make it twice as large.
*/
tmp = 2 *(c->ref_node_alsz * jnl_lebs) + c->leb_size - 1;
log_lebs = tmp /c->leb_size;
/* Plus one LEBreserved for commit */
log_lebs += 1;
if (c->leb_cnt -min_leb_cnt > 8) {
/* And someextra space to allow writes while committing */
log_lebs += 1;
min_leb_cnt +=1;
}
max_buds = jnl_lebs -log_lebs;
if (max_buds <UBIFS_MIN_BUD_LEBS)
max_buds =UBIFS_MIN_BUD_LEBS;
/*
* Orphan nodes are stored in a separate area.One node can store a lot
* of orphan inode numbers, but when new orphancomes we just add a new
* orphan node. At some point the nodes areconsolidated into one
* orphan node.
*/
//An orphan is an inodenumber whose inode node has been committed to the index with a link count ofzero. That happens when an open file is deleted (unlinked) and then a commit isrun
// The orphan area is afixed number of LEBs situated between the LPT area and the main area
// orphan 顾名思义是指牺牲者，在ubifs中的当一inode的引用为零的时候，这个文件需要被删除，为了防止在删除的时候发生unclean reboot，ubifs将这些需要删除的文件信息写在orphan area中，这样在发生unclean reboot的时候文件系统可以清楚的知道哪些文件需要被删除，而不是去扫描整个分区。文件系统在没有空余空间的时候也可以通过GC子系统来回收这些空间。关于orphan 的相关信息就保存在orphan area中，The orphan area is a fixed numberof LEBs situated between the LPT area and the main area
orph_lebs =UBIFS_MIN_ORPH_LEBS;
#ifdef CONFIG_UBIFS_FS_DEBUG
if (c->leb_cnt -min_leb_cnt > 1)
/*
* For debugging purposes it is better to haveat least 2
* orphan LEBs, because the orphan subsystemwould need to do
* consolidations and would be stressed more.
*/
orph_lebs += 1;
#endif
main_lebs =c->leb_cnt - UBIFS_SB_LEBS - UBIFS_MST_LEBS - log_lebs;
main_lebs -=orph_lebs;
//上面提到了，orphan区处于LPT区和main area之间。什么是LPT，LPT= LEB Properties Tree
lpt_first =UBIFS_LOG_LNUM + log_lebs;
c->lsave_cnt =DEFAULT_LSAVE_CNT;
c->max_leb_cnt =c->leb_cnt;
err = ubifs_create_dflt_lpt(c, &main_lebs,lpt_first, &lpt_lebs,
&big_lpt);
*********************************************************************************
ubifs_create_dflt_lpt算出LPT需要占用几块LEB,LPT是描述的ubifs中每一个leb的空闲bytes和dirty （这儿的脏好像并不是指被修改的意思，从代码pnode->lprops[0].dirty = iopos - node_sz;中大体的意思为没有被写，但是别人不能用的空间，因为flash操作的基本单元是page，如果在某一页中只写了一半的数据，那么另外一半就是脏的，虽然没有写东西，但是别人也用不了, Dirty space is thenumber of bytes taken up by obsolete nodes and padding, that can potentially bereclaimed by garbage collection）bytes。因为LPT区自己也占用了LEB，所以需要建立LPT自己的表。这想内核在启动的过程中建立自己的页表一样
a) 为跟index节点和根inode节点所占的leb创建LEB properties
b) 为其余所有的pnode节点建立信息，同时将信息写入flash media中
**********************************************************************************
if (err)
return err;
dbg_gen("LEBProperties Tree created (LEBs %d-%d)", lpt_first,
lpt_first +lpt_lebs - 1);
main_first =c->leb_cnt - main_lebs;
/* Create defaultsuperblock */
tmp =ALIGN(UBIFS_SB_NODE_SZ, c->min_io_size);
sup = kzalloc(tmp,GFP_KERNEL);
if (!sup)
return -ENOMEM;
tmp64 = (longlong)max_buds * c->leb_size;
if (big_lpt)
sup_flags |=UBIFS_FLG_BIGLPT;
//初始化superblock节点
sup->ch.node_type = UBIFS_SB_NODE;
sup->key_hash = UBIFS_KEY_HASH_R5;
sup->flags = cpu_to_le32(sup_flags);
sup->min_io_size = cpu_to_le32(c->min_io_size);
sup->leb_size = cpu_to_le32(c->leb_size);
sup->leb_cnt = cpu_to_le32(c->leb_cnt);
sup->max_leb_cnt = cpu_to_le32(c->max_leb_cnt);
sup->max_bud_bytes= cpu_to_le64(tmp64);
sup->log_lebs = cpu_to_le32(log_lebs);
sup->lpt_lebs = cpu_to_le32(lpt_lebs);
sup->orph_lebs = cpu_to_le32(orph_lebs);
sup->jhead_cnt = cpu_to_le32(DEFAULT_JHEADS_CNT);
sup->fanout = cpu_to_le32(DEFAULT_FANOUT);
sup->lsave_cnt = cpu_to_le32(c->lsave_cnt);
sup->fmt_version = cpu_to_le32(UBIFS_FORMAT_VERSION);
sup->time_gran = cpu_to_le32(DEFAULT_TIME_GRAN);
if(c->mount_opts.override_compr)
sup->default_compr= cpu_to_le16(c->mount_opts.compr_type);
else
sup->default_compr= cpu_to_le16(UBIFS_COMPR_LZO);
generate_random_uuid(sup->uuid);
main_bytes = (longlong)main_lebs * c->leb_size;
tmp64 = div_u64(main_bytes* DEFAULT_RP_PERCENT, 100);
if (tmp64 >DEFAULT_MAX_RP_SIZE)
tmp64 =DEFAULT_MAX_RP_SIZE;
sup->rp_size =cpu_to_le64(tmp64);
sup->ro_compat_version= cpu_to_le32(UBIFS_RO_COMPAT_VERSION);
//写入superblock 节点到LEB0
err =ubifs_write_node(c, sup, UBIFS_SB_NODE_SZ, 0, 0, UBI_LONGTERM);
kfree(sup);
if (err)
return err;
dbg_gen("defaultsuperblock created at LEB 0:0");
/* Create defaultmaster node */
mst =kzalloc(c->mst_node_alsz, GFP_KERNEL);
if (!mst)
return -ENOMEM;
//初始化master节点
mst->ch.node_type =UBIFS_MST_NODE;
mst->log_lnum = cpu_to_le32(UBIFS_LOG_LNUM);
mst->highest_inum =cpu_to_le64(UBIFS_FIRST_INO);
mst->cmt_no = 0;
mst->root_lnum = cpu_to_le32(main_first +DEFAULT_IDX_LEB);
mst->root_offs = 0;
tmp =ubifs_idx_node_sz(c, 1);
mst->root_len = cpu_to_le32(tmp);
mst->gc_lnum = cpu_to_le32(main_first +DEFAULT_GC_LEB);
mst->ihead_lnum = cpu_to_le32(main_first + DEFAULT_IDX_LEB);
mst->ihead_offs = cpu_to_le32(ALIGN(tmp,c->min_io_size));
mst->index_size = cpu_to_le64(ALIGN(tmp, 8));
mst->lpt_lnum = cpu_to_le32(c->lpt_lnum);
mst->lpt_offs = cpu_to_le32(c->lpt_offs);
mst->nhead_lnum = cpu_to_le32(c->nhead_lnum);
mst->nhead_offs = cpu_to_le32(c->nhead_offs);
mst->ltab_lnum = cpu_to_le32(c->ltab_lnum);
mst->ltab_offs = cpu_to_le32(c->ltab_offs);
mst->lsave_lnum = cpu_to_le32(c->lsave_lnum);
mst->lsave_offs = cpu_to_le32(c->lsave_offs);
mst->lscan_lnum = cpu_to_le32(main_first);
mst->empty_lebs = cpu_to_le32(main_lebs - 2);
mst->idx_lebs = cpu_to_le32(1);
mst->leb_cnt = cpu_to_le32(c->leb_cnt);
/* Calculate lpropsstatistics */
tmp64 = main_bytes;
tmp64 -=ALIGN(ubifs_idx_node_sz(c, 1), c->min_io_size);
tmp64 -=ALIGN(UBIFS_INO_NODE_SZ, c->min_io_size);
mst->total_free =cpu_to_le64(tmp64);
tmp64 =ALIGN(ubifs_idx_node_sz(c, 1), c->min_io_size);
ino_waste =ALIGN(UBIFS_INO_NODE_SZ, c->min_io_size) -
tmp64 += ino_waste;
tmp64 -=ALIGN(ubifs_idx_node_sz(c, 1), 8);
mst->total_dirty =cpu_to_le64(tmp64);
/* The indexing LEB does not contribute to darkspace */
tmp64 =(c->main_lebs - 1) * c->dark_wm;
mst->total_dark =cpu_to_le64(tmp64);
mst->total_used =cpu_to_le64(UBIFS_INO_NODE_SZ);
//master节点一式两份
err = ubifs_write_node(c,mst, UBIFS_MST_NODE_SZ, UBIFS_MST_LNUM, 0,
if (err) {
kfree(mst);
return err;
}
err =ubifs_write_node(c, mst, UBIFS_MST_NODE_SZ, UBIFS_MST_LNUM + 1, 0,
kfree(mst);
if (err)
return err;
dbg_gen("defaultmaster node created at LEB %d:0", UBIFS_MST_LNUM);
/* Create the rootindexing node */
tmp =ubifs_idx_node_sz(c, 1);
//idx节点。从tnc.c中的描述操作，idx的成员zbranch以及make_idx_node函数看来，idx节点是用来在flash media中保存TNC树的
内核用struct ubifs_znode结构体来代表着flash中的一个idx 节点。Idx节点的孩子代表真正的数据，当然这些数据本身可以是一个idx节点，也可以是当初的数据。
这儿初始化的是TNC的根节点。
//《a brief introduce of ubi and ubifs》中说inode节点和它的数据是分开的，上面的idx节点其实是存放的数据。那么struct ubifs_ino_node类型的节点是存放的inode吗？(yes)
// In UBIFS, inodes have a correspondinginode node which records the number of directory entry links, moresimply known as the link count.
// inode node is a node that holds themetadata for an inode. Every inode has
exactly one (non-obsolete) inode node.
idx =kzalloc(ALIGN(tmp, c->min_io_size), GFP_KERNEL);
if (!idx)
return -ENOMEM;
c->key_fmt =UBIFS_SIMPLE_KEY_FMT;
c->key_hash =key_r5_hash;
idx->ch.node_type =UBIFS_IDX_NODE;
idx->child_cnt =cpu_to_le16(1);
ino_key_init(c,&key, UBIFS_ROOT_INO);
br =ubifs_idx_branch(c, idx, 0);
key_write_idx(c,&key, &br->key);
br->lnum =cpu_to_le32(main_first + DEFAULT_DATA_LEB);
br->len = cpu_to_le32(UBIFS_INO_NODE_SZ);
err =ubifs_write_node(c, idx, tmp, main_first + DEFAULT_IDX_LEB, 0,
kfree(idx);
if (err)
return err;
dbg_gen("defaultroot indexing node created LEB %d:0",
main_first +DEFAULT_IDX_LEB);
/* Create default rootinode */
tmp =ALIGN(UBIFS_INO_NODE_SZ, c->min_io_size);
ino = kzalloc(tmp,GFP_KERNEL);
if (!ino)
return -ENOMEM;
ino_key_init_flash(c,&ino->key, UBIFS_ROOT_INO);
ino->ch.node_type =UBIFS_INO_NODE;
ino->creat_sqnum =cpu_to_le64(++c->max_sqnum);
ino->nlink =cpu_to_le32(2);
tmp_le64 =cpu_to_le64(CURRENT_TIME_SEC.tv_sec);
ino->atime_sec = tmp_le64;
ino->ctime_sec = tmp_le64;
ino->mtime_sec = tmp_le64;
ino->atime_nsec = 0;
ino->ctime_nsec = 0;
ino->mtime_nsec = 0;
ino->mode =cpu_to_le32(S_IFDIR | S_IRUGO | S_IWUSR | S_IXUGO);
ino->size =cpu_to_le64(UBIFS_INO_NODE_SZ);
/* Set compressionenabled by default */
ino->flags =cpu_to_le32(UBIFS_COMPR_FL);
err =ubifs_write_node(c, ino, UBIFS_INO_NODE_SZ,
main_first + DEFAULT_DATA_LEB, 0,
kfree(ino);
if (err)
return err;
dbg_gen("rootinode created at LEB %d:0",
main_first +DEFAULT_DATA_LEB);
/*
* The first node in the log has to be thecommit start node. This is
* always the case during normal file-systemoperation. Write a fake
* commit start node to the log.
*/
tmp =ALIGN(UBIFS_CS_NODE_SZ, c->min_io_size);
cs = kzalloc(tmp,GFP_KERNEL);
if (!cs)
return -ENOMEM;
cs->ch.node_type =UBIFS_CS_NODE;
//在log区域写入一个commit start node，每一次commit的时候会向log区域写入两种类型，一种就是commit start类型的节点表示一次commit的开始，两外一种就是referencr 节点，里面记录了相应的日志需要操作的leb，和offset。
err =ubifs_write_node(c, cs, UBIFS_CS_NODE_SZ, UBIFS_LOG_LNUM,
0, UBI_UNKNOWN);
kfree(cs);
ubifs_msg("defaultfile-system created");
return 0;
}
3.3 ubifs_read_master
读ubifs文件系统的master节点，我们前面提到了master节点是一式两份的，因为它里面保存的是idx的最基本的东西，不容有失。而且master节点是不能同时写的，防止unclean reboot使得两份数据同时被破坏
int ubifs_read_master(struct ubifs_info *c)
{
int err, old_leb_cnt;
c->mst_node =kzalloc(c->mst_node_alsz, GFP_KERNEL);
if (!c->mst_node)
return -ENOMEM;
//检查两份master节点，看是master中的数据是否被破坏。
err =scan_for_master(c);
if (err) {
if (err ==-EUCLEAN)
//如果被破坏，那么就需要恢复
err =ubifs_recover_master_node(c);
if (err)
/*
* Note, we do not free 'c->mst_node' herebecause the
* unmount routine will take care of this.
*/
returnerr;
}
/* Make sure that therecovery flag is clear */
//用master节点来初始化ubifs_info结构体中的信息
c->mst_node->flags&= cpu_to_le32(~UBIFS_MST_RCVRY);
c->max_sqnum =le64_to_cpu(c->mst_node->ch.sqnum);
c->highest_inum =le64_to_cpu(c->mst_node->highest_inum);
c->cmt_no = le64_to_cpu(c->mst_node->cmt_no);
c->zroot.lnum =le32_to_cpu(c->mst_node->root_lnum);
c->zroot.offs =le32_to_cpu(c->mst_node->root_offs);
c->zroot.len =le32_to_cpu(c->mst_node->root_len);
c->lhead_lnum =le32_to_cpu(c->mst_node->log_lnum);
c->gc_lnum =le32_to_cpu(c->mst_node->gc_lnum);
c->ihead_lnum =le32_to_cpu(c->mst_node->ihead_lnum);
c->ihead_offs =le32_to_cpu(c->mst_node->ihead_offs);
c->old_idx_sz =le64_to_cpu(c->mst_node->index_size);
c->lpt_lnum =le32_to_cpu(c->mst_node->lpt_lnum);
c->lpt_offs =le32_to_cpu(c->mst_node->lpt_offs);
c->nhead_lnum =le32_to_cpu(c->mst_node->nhead_lnum);
c->nhead_offs =le32_to_cpu(c->mst_node->nhead_offs);
c->ltab_lnum = le32_to_cpu(c->mst_node->ltab_lnum);
c->ltab_offs =le32_to_cpu(c->mst_node->ltab_offs);
c->lsave_lnum =le32_to_cpu(c->mst_node->lsave_lnum);
c->lsave_offs =le32_to_cpu(c->mst_node->lsave_offs);
c->lscan_lnum =le32_to_cpu(c->mst_node->lscan_lnum);
c->lst.empty_lebs = le32_to_cpu(c->mst_node->empty_lebs);
c->lst.idx_lebs = le32_to_cpu(c->mst_node->idx_lebs);
old_leb_cnt =le32_to_cpu(c->mst_node->leb_cnt);
c->lst.total_free = le64_to_cpu(c->mst_node->total_free);
c->lst.total_dirty= le64_to_cpu(c->mst_node->total_dirty);
c->lst.total_used = le64_to_cpu(c->mst_node->total_used);
c->lst.total_dead = le64_to_cpu(c->mst_node->total_dead);
c->lst.total_dark = le64_to_cpu(c->mst_node->total_dark);
c->calc_idx_sz =c->old_idx_sz;
if(c->mst_node->flags & cpu_to_le32(UBIFS_MST_NO_ORPHS))
c->no_orphs= 1;
if (old_leb_cnt !=c->leb_cnt) {
/* The filesystem has been resized */
int growth =c->leb_cnt - old_leb_cnt;
if(c->leb_cnt < old_leb_cnt ||
c->leb_cnt < UBIFS_MIN_LEB_CNT) {
ubifs_err("badleb_cnt on master node");
dbg_dump_node(c,c->mst_node);
return-EINVAL;
}
dbg_mnt("Autoresizing (master) from %d LEBs to %d LEBs",
old_leb_cnt,c->leb_cnt);
c->lst.empty_lebs+= growth;
c->lst.total_free+= growth * (long long)c->leb_size;
c->lst.total_dark+= growth * (long long)c->dark_wm;
/*
* Reflect changes back onto the master node.N.B. the master
* node gets written immediately whenevermounting (or
* remounting) in read-write mode, so we do notneed to write it
* here.
*/
c->mst_node->leb_cnt= cpu_to_le32(c->leb_cnt);
c->mst_node->empty_lebs= cpu_to_le32(c->lst.empty_lebs);
c->mst_node->total_free= cpu_to_le64(c->lst.total_free);
c->mst_node->total_dark= cpu_to_le64(c->lst.total_dark);
}
err =validate_master(c);
if (err)
return err;
err =dbg_old_index_check_init(c, &c->zroot);
return err;
}
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