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Message-Id: <188CB614-ADD9-4DE0-AC1A-0DD94043EC76@dilger.ca>
Date: Fri, 17 Jul 2020 05:16:09 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Lukas Czerner <lczerner@...hat.com>
Cc: linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH v2] ext4: handle read only external journal device
On Jul 17, 2020, at 3:06 AM, Lukas Czerner <lczerner@...hat.com> wrote:
>
> Ext4 uses blkdev_get_by_dev() to get the block_device for journal device
> which does check to see if the read-only block device was opened
> read-only.
>
> As a result ext4 will hapily proceed mounting the file system with
> external journal on read-only device. This is bad as we would not be
> able to use the journal leading to errors later on.
>
> Instead of simply failing to mount file system in this case, treat it in
> a similar way we treat internal journal on read-only device. Allow to
> mount with -o noload in read-only mode.
>
> This can be reproduced easily like this:
>
> mke2fs -F -O journal_dev $JOURNAL_DEV 100M
> mkfs.$FSTYPE -F -J device=$JOURNAL_DEV $FS_DEV
> blockdev --setro $JOURNAL_DEV
> mount $FS_DEV $MNT
> touch $MNT/file
> umount $MNT
>
> leading to error like this
>
> [ 1307.318713] ------------[ cut here ]------------
> [ 1307.323362] generic_make_request: Trying to write to read-only block-device dm-2 (partno 0)
> [ 1307.331741] WARNING: CPU: 36 PID: 3224 at block/blk-core.c:855 generic_make_request_checks+0x2c3/0x580
> [ 1307.341041] Modules linked in: ext4 mbcache jbd2 rfkill intel_rapl_msr intel_rapl_common isst_if_commd
> [ 1307.419445] CPU: 36 PID: 3224 Comm: jbd2/dm-2 Tainted: G W I 5.8.0-rc5 #2
> [ 1307.427359] Hardware name: Dell Inc. PowerEdge R740/01KPX8, BIOS 2.3.10 08/15/2019
> [ 1307.434932] RIP: 0010:generic_make_request_checks+0x2c3/0x580
> [ 1307.440676] Code: 94 03 00 00 48 89 df 48 8d 74 24 08 c6 05 cf 2b 18 01 01 e8 7f a4 ff ff 48 c7 c7 50e
> [ 1307.459420] RSP: 0018:ffffc0d70eb5fb48 EFLAGS: 00010286
> [ 1307.464646] RAX: 0000000000000000 RBX: ffff9b33b2978300 RCX: 0000000000000000
> [ 1307.471780] RDX: ffff9b33e12a81e0 RSI: ffff9b33e1298000 RDI: ffff9b33e1298000
> [ 1307.478913] RBP: ffff9b7b9679e0c0 R08: 0000000000000837 R09: 0000000000000024
> [ 1307.486044] R10: 0000000000000000 R11: ffffc0d70eb5f9f0 R12: 0000000000000400
> [ 1307.493177] R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000
> [ 1307.500308] FS: 0000000000000000(0000) GS:ffff9b33e1280000(0000) knlGS:0000000000000000
> [ 1307.508396] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 1307.514142] CR2: 000055eaf4109000 CR3: 0000003dee40a006 CR4: 00000000007606e0
> [ 1307.521273] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 1307.528407] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [ 1307.535538] PKRU: 55555554
> [ 1307.538250] Call Trace:
> [ 1307.540708] generic_make_request+0x30/0x340
> [ 1307.544985] submit_bio+0x43/0x190
> [ 1307.548393] ? bio_add_page+0x62/0x90
> [ 1307.552068] submit_bh_wbc+0x16a/0x190
> [ 1307.555833] jbd2_write_superblock+0xec/0x200 [jbd2]
> [ 1307.560803] jbd2_journal_update_sb_log_tail+0x65/0xc0 [jbd2]
> [ 1307.566557] jbd2_journal_commit_transaction+0x2ae/0x1860 [jbd2]
> [ 1307.572566] ? check_preempt_curr+0x7a/0x90
> [ 1307.576756] ? update_curr+0xe1/0x1d0
> [ 1307.580421] ? account_entity_dequeue+0x7b/0xb0
> [ 1307.584955] ? newidle_balance+0x231/0x3d0
> [ 1307.589056] ? __switch_to_asm+0x42/0x70
> [ 1307.592986] ? __switch_to_asm+0x36/0x70
> [ 1307.596918] ? lock_timer_base+0x67/0x80
> [ 1307.600851] kjournald2+0xbd/0x270 [jbd2]
> [ 1307.604873] ? finish_wait+0x80/0x80
> [ 1307.608460] ? commit_timeout+0x10/0x10 [jbd2]
> [ 1307.612915] kthread+0x114/0x130
> [ 1307.616152] ? kthread_park+0x80/0x80
> [ 1307.619816] ret_from_fork+0x22/0x30
> [ 1307.623400] ---[ end trace 27490236265b1630 ]---
>
> Signed-off-by: Lukas Czerner <lczerner@...hat.com>
Reviewed-by: Andreas Dilger <adilger@...ger.ca>
> ---
> v2: some stylistic and error message changes
>
> fs/ext4/super.c | 51 ++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 33 insertions(+), 18 deletions(-)
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 330957ed1f05..d925a1b16206 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -5077,6 +5077,7 @@ static int ext4_load_journal(struct super_block *sb,
> dev_t journal_dev;
> int err = 0;
> int really_read_only;
> + int journal_dev_ro;
>
> BUG_ON(!ext4_has_feature_journal(sb));
>
> @@ -5088,7 +5089,31 @@ static int ext4_load_journal(struct super_block *sb,
> } else
> journal_dev = new_decode_dev(le32_to_cpu(es->s_journal_dev));
>
> - really_read_only = bdev_read_only(sb->s_bdev);
> + if (journal_inum && journal_dev) {
> + ext4_msg(sb, KERN_ERR,
> + "filesystem has both journal inode and journal device!");
> + return -EINVAL;
> + }
> +
> + if (journal_inum) {
> + journal = ext4_get_journal(sb, journal_inum);
> + if (!journal)
> + return -EINVAL;
> + } else {
> + journal = ext4_get_dev_journal(sb, journal_dev);
> + if (!journal)
> + return -EINVAL;
> + }
> +
> + journal_dev_ro = bdev_read_only(journal->j_dev);
> + really_read_only = bdev_read_only(sb->s_bdev) | journal_dev_ro;
> +
> + if (journal_dev_ro && !sb_rdonly(sb)) {
> + ext4_msg(sb, KERN_ERR,
> + "journal device read-only, try mounting with '-o ro'");
> + err = -EROFS;
> + goto err_out;
> + }
>
> /*
> * Are we loading a blank journal or performing recovery after a
> @@ -5103,27 +5128,14 @@ static int ext4_load_journal(struct super_block *sb,
> ext4_msg(sb, KERN_ERR, "write access "
> "unavailable, cannot proceed "
> "(try mounting with noload)");
> - return -EROFS;
> + err = -EROFS;
> + goto err_out;
> }
> ext4_msg(sb, KERN_INFO, "write access will "
> "be enabled during recovery");
> }
> }
>
> - if (journal_inum && journal_dev) {
> - ext4_msg(sb, KERN_ERR, "filesystem has both journal "
> - "and inode journals!");
> - return -EINVAL;
> - }
> -
> - if (journal_inum) {
> - if (!(journal = ext4_get_journal(sb, journal_inum)))
> - return -EINVAL;
> - } else {
> - if (!(journal = ext4_get_dev_journal(sb, journal_dev)))
> - return -EINVAL;
> - }
> -
> if (!(journal->j_flags & JBD2_BARRIER))
> ext4_msg(sb, KERN_INFO, "barriers disabled");
>
> @@ -5143,8 +5155,7 @@ static int ext4_load_journal(struct super_block *sb,
>
> if (err) {
> ext4_msg(sb, KERN_ERR, "error loading journal");
> - jbd2_journal_destroy(journal);
> - return err;
> + goto err_out;
> }
>
> EXT4_SB(sb)->s_journal = journal;
> @@ -5159,6 +5170,10 @@ static int ext4_load_journal(struct super_block *sb,
> }
>
> return 0;
> +
> +err_out:
> + jbd2_journal_destroy(journal);
> + return err;
> }
>
> static int ext4_commit_super(struct super_block *sb, int sync)
> --
> 2.21.3
>
Cheers, Andreas
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