2020-09-24 07:33:25

by Zhang Yi

Subject: [PATCH v2 7/7] ext4: introduce ext4_sb_bread_unmovable() to replace sb_bread_unmovable()

Now we only use sb_bread_unmovable() to read superblock and descriptor
block at mount time, so there is no opportunity that we need to clear
buffer verified bit and also handle buffer write_io error bit. But for
the sake of unification, let's introduce ext4_sb_bread_unmovable() to
replace all sb_bread_unmovable(). After this patch, we stop using read
helpers in fs/buffer.c.

Signed-off-by: zhangyi (F) <[email protected]>
---
fs/ext4/ext4.h | 2 ++
fs/ext4/super.c | 38 +++++++++++++++++++++++++++++---------
2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 6da1419f6ee7..28b135a536b5 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2824,6 +2824,8 @@ extern int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count);
/* super.c */
extern struct buffer_head *ext4_sb_bread(struct super_block *sb,
sector_t block, int op_flags);
+extern struct buffer_head *ext4_sb_bread_unmovable(struct super_block *sb,
+ sector_t block);
extern void ext4_read_bh_nowait(struct buffer_head *bh, int op_flags,
bh_end_io_t *end_io);
extern int ext4_read_bh(struct buffer_head *bh, int op_flags,
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b24e68eff48d..2b5b6033b8e6 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -204,18 +204,19 @@ int ext4_read_bh_lock(struct buffer_head *bh, int op_flags, bool wait)
}

/*
- * This works like sb_bread() except it uses ERR_PTR for error
+ * This works like __bread_gfp() except it uses ERR_PTR for error
* returns. Currently with sb_bread it's impossible to distinguish
* between ENOMEM and EIO situations (since both result in a NULL
* return.
*/
-struct buffer_head *
-ext4_sb_bread(struct super_block *sb, sector_t block, int op_flags)
+static struct buffer_head *__ext4_sb_bread_gfp(struct super_block *sb,
+ sector_t block, int op_flags,
+ gfp_t gfp)
{
struct buffer_head *bh;
int ret;

- bh = sb_getblk(sb, block);
+ bh = sb_getblk_gfp(sb, block, gfp);
if (bh == NULL)
return ERR_PTR(-ENOMEM);
if (ext4_buffer_uptodate(bh))
@@ -229,6 +230,18 @@ ext4_sb_bread(struct super_block *sb, sector_t block, int op_flags)
return bh;
}

+struct buffer_head *ext4_sb_bread(struct super_block *sb, sector_t block,
+ int op_flags)
+{
+ return __ext4_sb_bread_gfp(sb, block, op_flags, __GFP_MOVABLE);
+}
+
+struct buffer_head *ext4_sb_bread_unmovable(struct super_block *sb,
+ sector_t block)
+{
+ return __ext4_sb_bread_gfp(sb, block, 0, 0);
+}
+
void ext4_sb_breadahead_unmovable(struct super_block *sb, sector_t block)
{
struct buffer_head *bh = sb_getblk_gfp(sb, block, 0);
@@ -3943,8 +3956,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
logical_sb_block = sb_block;
}

- if (!(bh = sb_bread_unmovable(sb, logical_sb_block))) {
+ bh = ext4_sb_bread_unmovable(sb, logical_sb_block);
+ if (IS_ERR(bh)) {
ext4_msg(sb, KERN_ERR, "unable to read superblock");
+ ret = PTR_ERR(bh);
+ bh = NULL;
goto out_fail;
}
/*
@@ -4340,10 +4356,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
brelse(bh);
logical_sb_block = sb_block * EXT4_MIN_BLOCK_SIZE;
offset = do_div(logical_sb_block, blocksize);
- bh = sb_bread_unmovable(sb, logical_sb_block);
- if (!bh) {
+ bh = ext4_sb_bread_unmovable(sb, logical_sb_block);
+ if (IS_ERR(bh)) {
ext4_msg(sb, KERN_ERR,
"Can't read superblock on 2nd try");
+ ret = PTR_ERR(bh);
+ bh = NULL;
goto failed_mount;
}
es = (struct ext4_super_block *)(bh->b_data + offset);
@@ -4562,11 +4580,13 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
struct buffer_head *bh;

block = descriptor_loc(sb, logical_sb_block, i);
- bh = sb_bread_unmovable(sb, block);
- if (!bh) {
+ bh = ext4_sb_bread_unmovable(sb, block);
+ if (IS_ERR(bh)) {
ext4_msg(sb, KERN_ERR,
"can't read group descriptor %d", i);
db_count = i;
+ ret = PTR_ERR(bh);
+ bh = NULL;
goto failed_mount2;
}
rcu_read_lock();
--
2.25.4

2020-10-09 03:57:01

by Theodore Ts'o

Subject: Re: [PATCH v2 7/7] ext4: introduce ext4_sb_bread_unmovable() to replace sb_bread_unmovable()

On Thu, Sep 24, 2020 at 03:33:37PM +0800, zhangyi (F) wrote:
> Now we only use sb_bread_unmovable() to read superblock and descriptor
> block at mount time, so there is no opportunity that we need to clear
> buffer verified bit and also handle buffer write_io error bit. But for
> the sake of unification, let's introduce ext4_sb_bread_unmovable() to
> replace all sb_bread_unmovable(). After this patch, we stop using read
> helpers in fs/buffer.c.
>
> Signed-off-by: zhangyi (F) <[email protected]>

Thanks, applied.

- Ted