[PATCH -next v4 3/3] ext4: simplify read_mmp_block fucntion

Ye Bin
2021-10-19T12:27:08Z

This patch is according to Jan Kara's suggestion:
I guess I would just get rid of sb_getblk() in read_mmp_block() and always
expect valid bh passed. The only place that passes NULL bh after this
patch is one case in ext4_multi_mount_protect() and that can call
sb_getblk() on its own. That way we can also simplify read_mmp_block()
prototype to:

static int read_mmp_block(struct super_block *sb, struct buffer_head *bh);

Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
fs/ext4/mmp.c | 44 +++++++++++++++++++-------------------------
1 file changed, 19 insertions(+), 25 deletions(-)

diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index 9788c617e593..3a7370c88934 100644
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -64,33 +64,26 @@ static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
/*
* Read the MMP block. It _must_ be read from disk and hence we clear the
* uptodate flag on the buffer.
+ * Caller must ensure pass valid 'bh'.
*/
-static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
- ext4_fsblk_t mmp_block)
+static int read_mmp_block(struct super_block *sb, struct buffer_head *bh)
{
struct mmp_struct *mmp;
int ret;

- if (*bh)
- clear_buffer_uptodate(*bh);
-
- /* This would be sb_bread(sb, mmp_block), except we need to be sure
- * that the MD RAID device cache has been bypassed, and that the read
- * is not blocked in the elevator. */
- if (!*bh) {
- *bh = sb_getblk(sb, mmp_block);
- if (!*bh) {
- ret = -ENOMEM;
- goto warn_exit;
- }
+ if (!bh) {
+ ret = -EINVAL;
+ goto warn_exit;
}

- lock_buffer(*bh);
- ret = ext4_read_bh(*bh, REQ_META | REQ_PRIO, NULL);
+ clear_buffer_uptodate(bh);
+
+ lock_buffer(bh);
+ ret = ext4_read_bh(bh, REQ_META | REQ_PRIO, NULL);
if (ret)
goto warn_exit;

- mmp = (struct mmp_struct *)((*bh)->b_data);
+ mmp = (struct mmp_struct *)((bh)->b_data);
if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC) {
ret = -EFSCORRUPTED;
goto warn_exit;
@@ -101,10 +94,7 @@ static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
}
return 0;
warn_exit:
- brelse(*bh);
- *bh = NULL;
- ext4_warning(sb, "Error %d while reading MMP block %llu",
- ret, mmp_block);
+ ext4_warning(sb, "Error %d while reading MMP block", ret);
return ret;
}

@@ -195,7 +185,7 @@ static int kmmpd(void *data)
*/
diff = jiffies - last_update_time;
if (diff > mmp_check_interval * HZ) {
- retval = read_mmp_block(sb, &bh, mmp_block);
+ retval = read_mmp_block(sb, bh);
if (retval) {
ext4_error_err(sb, -retval,
"error reading MMP data: %d",
@@ -289,7 +279,11 @@ int ext4_multi_mount_protect(struct super_block *sb,
goto failed;
}

- retval = read_mmp_block(sb, &bh, mmp_block);
+ bh = sb_getblk(sb, mmp_block);
+ if (bh)
+ goto failed;
+
+ retval = read_mmp_block(sb, bh);
if (retval)
goto failed;

@@ -327,7 +321,7 @@ int ext4_multi_mount_protect(struct super_block *sb,
goto failed;
}

- retval = read_mmp_block(sb, &bh, mmp_block);
+ retval = read_mmp_block(sb, bh);
if (retval)
goto failed;
mmp = (struct mmp_struct *)(bh->b_data);
@@ -356,7 +350,7 @@ int ext4_multi_mount_protect(struct super_block *sb,
goto failed;
}

- retval = read_mmp_block(sb, &bh, mmp_block);
+ retval = read_mmp_block(sb, bh);
if (retval)
goto failed;
mmp = (struct mmp_struct *)(bh->b_data);
--
2.31.1