Re: [PATCH 3/3] exfat: set EXFAT_SB_DIRTY and VOL_DIRTY at the same timing

From: Tetsuhiro Kohada
Date: Sat Jun 06 2020 - 05:27:53 EST

On 2020/06/05 16:32, Namjae Jeon wrote:
Set EXFAT_SB_DIRTY flag in exfat_put_super().

In some cases, can't clear VOL_DIRTY with 'sync'.
ex:

VOL_DIRTY is set when rmdir starts, but when non-empty-dir is detected, return error without setting
EXFAT_SB_DIRTY.
If performe 'sync' in this state, VOL_DIRTY will not be cleared.
Good catch.

Can you split this patch into two? (Don't set VOL_DIRTY on -ENOTEMPTY and Setting EXFAT_SB_DIRTY is
merged into exfat_set_vol_flag). I need to check the second one more.

Can't do that.

exfat_set_vol_flag() is called when rmdir processing begins. When Not-empty is detected,
VOL_DIRTY has already been written and synced to the media.

This sequence is same as other write functions.
<begin writing function>
set VOL_DIRTY (write to the media)
preparation/state analysis
update bh & set SB_DIRTY
clear VOL_DIRTY (cached)
<end>

SB_DIRTY is set when updating bh.
However, in some cases SB_DIRTY is not set.
If SB_DIRTY is not set, exfat_sync_fs() does nothing.

I thought there was a problem with separating VOL_DIRTY and SB_DIRTY.
So I investigated the timing when these are set. Attach the caller graph.
The green box is a function that sets SB_DIRTY directly.
The red box is a function that calls exfat_set_vol_flag() and sets VOL_DIRTY.
VOL_DIRTY is set on all paths before setting SB_DIRTY.

I think VOL_DIRTY and SB_DIRTY should be set at the same time.
That way, It is not necessary to set SB_DIRTY when updating bh.

<begin writing function>
set VOL_DIRTY (actually write on media), and set SB_DIRTY
preparation/state analysis
update data
clear VOL_DIRTY (cached)
<end>

By doing this, sync is guaranteed if VOL_DIRTY is set by calling exfat_set_vol_flag.

This change may still have problems, but it's little better than before, I think.

BR
---
Tetsuhiro Kohada <kohada.t2@xxxxxxxxx>



Thanks!

Signed-off-by: Tetsuhiro Kohada <kohada.t2@xxxxxxxxx>
---
fs/exfat/balloc.c | 4 ++--
fs/exfat/dir.c | 18 ++++++++----------
fs/exfat/exfat_fs.h | 2 +-
fs/exfat/fatent.c | 6 +-----
fs/exfat/misc.c | 3 +--
fs/exfat/namei.c | 12 ++++++------
fs/exfat/super.c | 3 +++
7 files changed, 22 insertions(+), 26 deletions(-)

diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c index 4055eb00ea9b..a987919686c0 100644
--- a/fs/exfat/balloc.c
+++ b/fs/exfat/balloc.c
@@ -158,7 +158,7 @@ int exfat_set_bitmap(struct inode *inode, unsigned int clu)
b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);

set_bit_le(b, sbi->vol_amap[i]->b_data);
- exfat_update_bh(sb, sbi->vol_amap[i], IS_DIRSYNC(inode));
+ exfat_update_bh(sbi->vol_amap[i], IS_DIRSYNC(inode));
return 0;
}

@@ -180,7 +180,7 @@ void exfat_clear_bitmap(struct inode *inode, unsigned int clu)
b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);

clear_bit_le(b, sbi->vol_amap[i]->b_data);
- exfat_update_bh(sb, sbi->vol_amap[i], IS_DIRSYNC(inode));
+ exfat_update_bh(sbi->vol_amap[i], IS_DIRSYNC(inode));

if (opts->discard) {
int ret_discard;
diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c index 3eb8386fb5f2..96c9a817d928 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -468,7 +468,7 @@ int exfat_init_dir_entry(struct inode *inode, struct exfat_chain *p_dir,
&ep->dentry.file.access_date,
NULL);

- exfat_update_bh(sb, bh, IS_DIRSYNC(inode));
+ exfat_update_bh(bh, IS_DIRSYNC(inode));
brelse(bh);

ep = exfat_get_dentry(sb, p_dir, entry + 1, &bh, &sector); @@ -478,7 +478,7 @@ int
exfat_init_dir_entry(struct inode *inode, struct exfat_chain *p_dir,
exfat_init_stream_entry(ep,
(type == TYPE_FILE) ? ALLOC_FAT_CHAIN : ALLOC_NO_FAT_CHAIN,
start_clu, size);
- exfat_update_bh(sb, bh, IS_DIRSYNC(inode));
+ exfat_update_bh(bh, IS_DIRSYNC(inode));
brelse(bh);

return 0;
@@ -514,7 +514,7 @@ int exfat_update_dir_chksum(struct inode *inode, struct exfat_chain *p_dir,
}

fep->dentry.file.checksum = cpu_to_le16(chksum);
- exfat_update_bh(sb, fbh, IS_DIRSYNC(inode));
+ exfat_update_bh(fbh, IS_DIRSYNC(inode));
release_fbh:
brelse(fbh);
return ret;
@@ -536,7 +536,7 @@ int exfat_init_ext_entry(struct inode *inode, struct exfat_chain *p_dir,
return -EIO;

ep->dentry.file.num_ext = (unsigned char)(num_entries - 1);
- exfat_update_bh(sb, bh, sync);
+ exfat_update_bh(bh, sync);
brelse(bh);

ep = exfat_get_dentry(sb, p_dir, entry + 1, &bh, &sector); @@ -545,7 +545,7 @@ int
exfat_init_ext_entry(struct inode *inode, struct exfat_chain *p_dir,

ep->dentry.stream.name_len = p_uniname->name_len;
ep->dentry.stream.name_hash = cpu_to_le16(p_uniname->name_hash);
- exfat_update_bh(sb, bh, sync);
+ exfat_update_bh(bh, sync);
brelse(bh);

for (i = EXFAT_FIRST_CLUSTER; i < num_entries; i++) { @@ -554,7 +554,7 @@ int
exfat_init_ext_entry(struct inode *inode, struct exfat_chain *p_dir,
return -EIO;

exfat_init_name_entry(ep, uniname);
- exfat_update_bh(sb, bh, sync);
+ exfat_update_bh(bh, sync);
brelse(bh);
uniname += EXFAT_FILE_NAME_LEN;
}
@@ -578,7 +578,7 @@ int exfat_remove_entries(struct inode *inode, struct exfat_chain *p_dir,
return -EIO;

exfat_set_entry_type(ep, TYPE_DELETED);
- exfat_update_bh(sb, bh, IS_DIRSYNC(inode));
+ exfat_update_bh(bh, IS_DIRSYNC(inode));
brelse(bh);
}

@@ -606,10 +606,8 @@ int exfat_free_dentry_set(struct exfat_entry_set_cache *es, int sync) {
int i, err = 0;

- if (es->modified) {
- set_bit(EXFAT_SB_DIRTY, &EXFAT_SB(es->sb)->s_state);
+ if (es->modified)
err = exfat_update_bhs(es->bh, es->num_bh, sync);
- }

for (i = 0; i < es->num_bh; i++)
err ? bforget(es->bh[i]):brelse(es->bh[i]);
diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h index f4fa0e833486..0e094d186612 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -514,7 +514,7 @@ void exfat_set_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
u8 *tz, __le16 *time, __le16 *date, u8 *time_cs);
u16 exfat_calc_chksum16(void *data, int len, u16 chksum, int type);
u32 exfat_calc_chksum32(void *data, int len, u32 chksum, int type); -void exfat_update_bh(struct
super_block *sb, struct buffer_head *bh, int sync);
+void exfat_update_bh(struct buffer_head *bh, int sync);
int exfat_update_bhs(struct buffer_head **bhs, int nr_bhs, int sync); void exfat_chain_set(struct
exfat_chain *ec, unsigned int dir,
unsigned int size, unsigned char flags); diff --git a/fs/exfat/fatent.c
b/fs/exfat/fatent.c index 5d11bc2f1b68..f8171183b4c1 100644
--- a/fs/exfat/fatent.c
+++ b/fs/exfat/fatent.c
@@ -75,7 +75,7 @@ int exfat_ent_set(struct super_block *sb, unsigned int loc,

fat_entry = (__le32 *)&(bh->b_data[off]);
*fat_entry = cpu_to_le32(content);
- exfat_update_bh(sb, bh, sb->s_flags & SB_SYNCHRONOUS);
+ exfat_update_bh(bh, sb->s_flags & SB_SYNCHRONOUS);
exfat_mirror_bh(sb, sec, bh);
brelse(bh);
return 0;
@@ -174,7 +174,6 @@ int exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain)
return -EIO;
}

- set_bit(EXFAT_SB_DIRTY, &sbi->s_state);
clu = p_chain->dir;

if (p_chain->flags == ALLOC_NO_FAT_CHAIN) { @@ -261,7 +260,6 @@ int exfat_zeroed_cluster(struct
inode *dir, unsigned int clu)
memset(bhs[n]->b_data, 0, sb->s_blocksize);
}

- set_bit(EXFAT_SB_DIRTY, &sbi->s_state);
err = exfat_update_bhs(bhs, n, IS_DIRSYNC(dir));
if (err)
goto release_bhs;
@@ -326,8 +324,6 @@ int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
}
}

- set_bit(EXFAT_SB_DIRTY, &sbi->s_state);
-
p_chain->dir = EXFAT_EOF_CLUSTER;

while ((new_clu = exfat_find_free_bitmap(sb, hint_clu)) != diff --git a/fs/exfat/misc.c
b/fs/exfat/misc.c index dc34968e99d3..564718747fb2 100644
--- a/fs/exfat/misc.c
+++ b/fs/exfat/misc.c
@@ -163,9 +163,8 @@ u32 exfat_calc_chksum32(void *data, int len, u32 chksum, int type)
return chksum;
}

-void exfat_update_bh(struct super_block *sb, struct buffer_head *bh, int sync)
+void exfat_update_bh(struct buffer_head *bh, int sync)
{
- set_bit(EXFAT_SB_DIRTY, &EXFAT_SB(sb)->s_state);
set_buffer_uptodate(bh);
mark_buffer_dirty(bh);

diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c index 5b0f35329d63..e36c9fc4a5d6 100644
--- a/fs/exfat/namei.c
+++ b/fs/exfat/namei.c
@@ -387,7 +387,7 @@ static int exfat_find_empty_entry(struct inode *inode,
ep->dentry.stream.valid_size = cpu_to_le64(size);
ep->dentry.stream.size = ep->dentry.stream.valid_size;
ep->dentry.stream.flags = p_dir->flags;
- exfat_update_bh(sb, bh, IS_DIRSYNC(inode));
+ exfat_update_bh(bh, IS_DIRSYNC(inode));
brelse(bh);
if (exfat_update_dir_chksum(inode, &(ei->dir),
ei->entry))
@@ -1071,7 +1071,7 @@ static int exfat_rename_file(struct inode *inode, struct exfat_chain *p_dir,
epnew->dentry.file.attr |= cpu_to_le16(ATTR_ARCHIVE);
ei->attr |= ATTR_ARCHIVE;
}
- exfat_update_bh(sb, new_bh, sync);
+ exfat_update_bh(new_bh, sync);
brelse(old_bh);
brelse(new_bh);

@@ -1083,7 +1083,7 @@ static int exfat_rename_file(struct inode *inode, struct exfat_chain *p_dir,
return -EIO;

memcpy(epnew, epold, DENTRY_SIZE);
- exfat_update_bh(sb, new_bh, sync);
+ exfat_update_bh(new_bh, sync);
brelse(old_bh);
brelse(new_bh);

@@ -1100,7 +1100,7 @@ static int exfat_rename_file(struct inode *inode, struct exfat_chain *p_dir,
epold->dentry.file.attr |= cpu_to_le16(ATTR_ARCHIVE);
ei->attr |= ATTR_ARCHIVE;
}
- exfat_update_bh(sb, old_bh, sync);
+ exfat_update_bh(old_bh, sync);
brelse(old_bh);
ret = exfat_init_ext_entry(inode, p_dir, oldentry,
num_new_entries, p_uniname);
@@ -1155,7 +1155,7 @@ static int exfat_move_file(struct inode *inode, struct exfat_chain *p_olddir,
epnew->dentry.file.attr |= cpu_to_le16(ATTR_ARCHIVE);
ei->attr |= ATTR_ARCHIVE;
}
- exfat_update_bh(sb, new_bh, IS_DIRSYNC(inode));
+ exfat_update_bh(new_bh, IS_DIRSYNC(inode));
brelse(mov_bh);
brelse(new_bh);

@@ -1167,7 +1167,7 @@ static int exfat_move_file(struct inode *inode, struct exfat_chain *p_olddir,
return -EIO;

memcpy(epnew, epmov, DENTRY_SIZE);
- exfat_update_bh(sb, new_bh, IS_DIRSYNC(inode));
+ exfat_update_bh(new_bh, IS_DIRSYNC(inode));
brelse(mov_bh);
brelse(new_bh);

diff --git a/fs/exfat/super.c b/fs/exfat/super.c index e650e65536f8..199a1e78f9e5 100644
--- a/fs/exfat/super.c
+++ b/fs/exfat/super.c
@@ -104,6 +104,9 @@ int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flag)
struct boot_sector *p_boot = (struct boot_sector *)sbi->boot_bh->b_data;
bool sync;

+ if (new_flag == VOL_DIRTY)
+ set_bit(EXFAT_SB_DIRTY, &sbi->s_state);
+
/* flags are not changed */
if (sbi->vol_flag == new_flag)
return 0;
--
2.25.1


Attachment: exfat__fs_8h_a9aac0f25e9499af92c7ac753f1bcb049_icgraph.png
Description: PNG image