From: Johannes Thumshirn <Johannes.Thumshirn@wdc.com>
To: Nikolay Borisov <nborisov@suse.com>, David Sterba <dsterba@suse.com>
Cc: "linux-btrfs @ vger . kernel . org" <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH v2 2/6] btrfs: remove buffer heads from super block reading
Date: Thu, 23 Jan 2020 16:45:28 +0000 [thread overview]
Message-ID: <SN4PR0401MB359865C6D227012D2E71CF5B9B0F0@SN4PR0401MB3598.namprd04.prod.outlook.com> (raw)
In-Reply-To: fa80a24c-e174-ec21-9228-8ff5fc415c72@suse.com
[-- Attachment #1: Type: text/plain, Size: 1944 bytes --]
On 23/01/2020 15:14, Nikolay Borisov wrote:
>
>
> On 23.01.20 г. 10:18 ч., Johannes Thumshirn wrote:
>
> <snip>
>
>> @@ -3374,40 +3378,60 @@ static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate)
>> }
>>
>> int btrfs_read_dev_one_super(struct block_device *bdev, int copy_num,
>> - struct buffer_head **bh_ret)
>> + struct page **super_page)
>> {
>> - struct buffer_head *bh;
>> struct btrfs_super_block *super;
>> + struct bio_vec bio_vec;
>> + struct bio bio;
>> + struct page *page;
>> u64 bytenr;
>> + struct address_space *mapping = bdev->bd_inode->i_mapping;
>> + gfp_t gfp_mask;
>> + int ret;
>>
>> bytenr = btrfs_sb_offset(copy_num);
>> if (bytenr + BTRFS_SUPER_INFO_SIZE >= i_size_read(bdev->bd_inode))
>> return -EINVAL;
>>
>> - bh = __bread(bdev, bytenr / BTRFS_BDEV_BLOCKSIZE, BTRFS_SUPER_INFO_SIZE);
>> + gfp_mask = mapping_gfp_constraint(mapping, ~__GFP_FS) | __GFP_NOFAIL;
>> + page = find_or_create_page(mapping, bytenr >> PAGE_SHIFT, gfp_mask);
>> + if (!page)
>> + return -ENOMEM;
>> +
>> + bio_init(&bio, &bio_vec, 1);
>> + bio.bi_iter.bi_sector = bytenr >> SECTOR_SHIFT;
>> + bio_set_dev(&bio, bdev);
>> + bio_set_op_attrs(&bio, REQ_OP_READ, 0);
>> + bio_add_page(&bio, page, BTRFS_SUPER_INFO_SIZE,
>> + offset_in_page(bytenr));
>> +
>> + ret = submit_bio_wait(&bio);
>> + unlock_page(page);
>
> So this is based on my code where the page is unlocked as soon as it's
> read. However, as per out off-list discussion, I think this page needs
> to be unlocked once the caller of
> btrfs_read_dev_one_super/btrfs_read_dev_super is finished with it.
As I don't have an answer to that yet, I just gave it a try (see
attached diff) and it instantly deadlocks on mount. So either I did
something wrong or holding the lock until the callers have finished
processing it is a bad idea.
Thanks,
Johannes
[-- Attachment #2: disk-io.c.patch --]
[-- Type: text/plain, Size: 2406 bytes --]
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index ac1755793596..7afac96be17f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2856,6 +2856,7 @@ int __cold open_ctree(struct super_block *sb,
ret = btrfs_init_csum_hash(fs_info, csum_type);
if (ret) {
err = ret;
+ unlock_page(super_page);
btrfs_release_disk_super(super_page);
goto fail_alloc;
}
@@ -2867,6 +2868,7 @@ int __cold open_ctree(struct super_block *sb,
if (btrfs_check_super_csum(fs_info, superblock)) {
btrfs_err(fs_info, "superblock checksum mismatch");
err = -EINVAL;
+ unlock_page(super_page);
btrfs_release_disk_super(super_page);
goto fail_csum;
}
@@ -2877,6 +2879,7 @@ int __cold open_ctree(struct super_block *sb,
* the whole block of INFO_SIZE
*/
memcpy(fs_info->super_copy, superblock, sizeof(*fs_info->super_copy));
+ unlock_page(super_page);
btrfs_release_disk_super(super_page);
disk_super = fs_info->super_copy;
@@ -3413,7 +3416,6 @@ int btrfs_read_dev_one_super(struct block_device *bdev, int copy_num,
offset_in_page(bytenr));
ret = submit_bio_wait(&bio);
- unlock_page(page);
/*
* If we fail to read from the underlying devices, as of now
* the best option we have is to mark it EIO.
@@ -3426,6 +3428,7 @@ int btrfs_read_dev_one_super(struct block_device *bdev, int copy_num,
super = kmap(page);
if (btrfs_super_bytenr(super) != bytenr ||
btrfs_super_magic(super) != BTRFS_MAGIC) {
+ unlock_page(page);
btrfs_release_disk_super(page);
return -EINVAL;
}
@@ -3457,11 +3460,14 @@ int btrfs_read_dev_super(struct block_device *bdev, struct page **page)
super = kmap(*page);
if (!latest || btrfs_super_generation(super) > transid) {
- if (latest)
+ if (latest) {
+ unlock_page(latest);
btrfs_release_disk_super(latest);
+ }
latest = *page;
transid = btrfs_super_generation(super);
} else {
+ unlock_page(*page);
btrfs_release_disk_super(*page);
}
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f4a6ee518f0c..8bb2f9dead63 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -7344,7 +7344,6 @@ void btrfs_scratch_superblocks(struct block_device *bdev, const char *device_pat
bio_add_page(&bio, page, BTRFS_SUPER_INFO_SIZE,
offset_in_page(bytenr));
- lock_page(page);
submit_bio_wait(&bio);
unlock_page(page);
btrfs_release_disk_super(page);
next prev parent reply other threads:[~2020-01-23 16:45 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-23 8:18 [PATCH v2 0/6] btrfs: remove buffer heads form superblock handling Johannes Thumshirn
2020-01-23 8:18 ` [PATCH v2 1/6] btrfs: export btrfs_release_disk_super Johannes Thumshirn
2020-01-23 13:42 ` Josef Bacik
2020-01-23 8:18 ` [PATCH v2 2/6] btrfs: remove buffer heads from super block reading Johannes Thumshirn
2020-01-23 13:51 ` Josef Bacik
2020-01-23 13:53 ` Johannes Thumshirn
2020-01-23 14:13 ` Nikolay Borisov
2020-01-23 16:45 ` Johannes Thumshirn [this message]
2020-01-23 22:25 ` David Sterba
2020-01-24 13:54 ` David Sterba
2020-01-24 14:03 ` David Sterba
2020-01-23 8:18 ` [PATCH v2 3/6] btrfs: remove use of buffer_heads from superblock writeout Johannes Thumshirn
2020-01-23 13:59 ` Josef Bacik
2020-01-23 14:19 ` Nikolay Borisov
2020-01-24 14:15 ` David Sterba
2020-01-23 8:18 ` [PATCH v2 4/6] btrfs: remove btrfsic_submit_bh() Johannes Thumshirn
2020-01-23 14:00 ` Josef Bacik
2020-01-23 8:18 ` [PATCH v2 5/6] btrfs: remove buffer_heads from btrfsic_process_written_block() Johannes Thumshirn
2020-01-23 14:00 ` Josef Bacik
2020-01-23 8:18 ` [PATCH v2 6/6] btrfs: remove buffer_heads form superblock mirror integrity checking Johannes Thumshirn
2020-01-23 14:03 ` Josef Bacik
2020-01-23 14:23 ` Nikolay Borisov
2020-01-24 14:22 ` David Sterba
2020-01-24 14:59 ` Johannes Thumshirn
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=SN4PR0401MB359865C6D227012D2E71CF5B9B0F0@SN4PR0401MB3598.namprd04.prod.outlook.com \
--to=johannes.thumshirn@wdc.com \
--cc=dsterba@suse.com \
--cc=linux-btrfs@vger.kernel.org \
--cc=nborisov@suse.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.