Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-11-22 12:11:40 +00:00
Code Issues Packages Projects Releases Wiki Activity

bcachefs: Fix race in bch2_write_super()

Browse Source 
bch2_write_super() was looping over online devices multiple times -
dropping and retaking io_ref each time.

This meant it could race with device removal; it could increment the
sequence number on a device but fail to write it - and then if the
device was re-added, it would get confused the next time around thinking
a superblock write was silently dropped.

Fix this by taking io_ref once, and stashing pointers to online devices
in a darray.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-05-06 20:49:24 -04:00
parent 71dac2482a
commit 54541c1f78
1 changed files with 32 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
fs/bcachefs/super-io.c
View File

@ -923,6 +923,7 @@ int bch2_write_super(struct bch_fs *c)
struct bch_devs_mask sb_written;
bool wrote, can_mount_without_written, can_mount_with_written;
unsigned degraded_flags = BCH_FORCE_IF_DEGRADED;
DARRAY(struct bch_dev *) online_devices = {};
int ret = 0;
trace_and_count(c, write_super, c, _RET_IP_);
@ -935,6 +936,15 @@ int bch2_write_super(struct bch_fs *c)
closure_init_stack(cl);
memset(&sb_written, 0, sizeof(sb_written));
for_each_online_member(c, ca) {
ret = darray_push(&online_devices, ca);
if (bch2_fs_fatal_err_on(ret, c, "%s: error allocating online devices", __func__)) {
percpu_ref_put(&ca->io_ref);
goto out;
}
percpu_ref_get(&ca->io_ref);
}
/* Make sure we're using the new magic numbers: */
c->disk_sb.sb->magic = BCHFS_MAGIC;
c->disk_sb.sb->layout.magic = BCHFS_MAGIC;
@ -942,8 +952,8 @@ int bch2_write_super(struct bch_fs *c)
le64_add_cpu(&c->disk_sb.sb->seq, 1);
struct bch_sb_field_members_v2 *mi = bch2_sb_field_get(c->disk_sb.sb, members_v2);
for_each_online_member(c, ca)
__bch2_members_v2_get_mut(mi, ca->dev_idx)->seq = c->disk_sb.sb->seq;
darray_for_each(online_devices, ca)
__bch2_members_v2_get_mut(mi, (*ca)->dev_idx)->seq = c->disk_sb.sb->seq;
c->disk_sb.sb->write_time = cpu_to_le64(ktime_get_real_seconds());
if (test_bit(BCH_FS_error, &c->flags))
@ -959,16 +969,15 @@ int bch2_write_super(struct bch_fs *c)
bch2_sb_errors_from_cpu(c);
bch2_sb_downgrade_update(c);
for_each_online_member(c, ca)
bch2_sb_from_fs(c, ca);
darray_for_each(online_devices, ca)
bch2_sb_from_fs(c, (*ca));
for_each_online_member(c, ca) {
darray_for_each(online_devices, ca) {
printbuf_reset(&err);
ret = bch2_sb_validate(&ca->disk_sb, &err, WRITE);
ret = bch2_sb_validate(&(*ca)->disk_sb, &err, WRITE);
if (ret) {
bch2_fs_inconsistent(c, "sb invalid before write: %s", err.buf);
percpu_ref_put(&ca->io_ref);
goto out;
}
}
@ -995,16 +1004,18 @@ int bch2_write_super(struct bch_fs *c)
return -BCH_ERR_sb_not_downgraded;
}
for_each_online_member(c, ca) {
__set_bit(ca->dev_idx, sb_written.d);
ca->sb_write_error = 0;
darray_for_each(online_devices, ca) {
__set_bit((*ca)->dev_idx, sb_written.d);
(*ca)->sb_write_error = 0;
}
for_each_online_member(c, ca)
read_back_super(c, ca);
darray_for_each(online_devices, ca)
read_back_super(c, *ca);
closure_sync(cl);
for_each_online_member(c, ca) {
darray_for_each(online_devices, cap) {
struct bch_dev *ca = *cap;
if (ca->sb_write_error)
continue;
@ -1031,17 +1042,20 @@ int bch2_write_super(struct bch_fs *c)
do {
wrote = false;
for_each_online_member(c, ca)
darray_for_each(online_devices, cap) {
struct bch_dev *ca = *cap;
if (!ca->sb_write_error &&
sb < ca->disk_sb.sb->layout.nr_superblocks) {
write_one_super(c, ca, sb);
wrote = true;
}
}
closure_sync(cl);
sb++;
} while (wrote);
for_each_online_member(c, ca) {
darray_for_each(online_devices, cap) {
struct bch_dev *ca = *cap;
if (ca->sb_write_error)
__clear_bit(ca->dev_idx, sb_written.d);
else
@ -1077,6 +1091,9 @@ int bch2_write_super(struct bch_fs *c)
out:
/* Make new options visible after they're persistent: */
bch2_sb_update(c);
darray_for_each(online_devices, ca)
percpu_ref_put(&(*ca)->io_ref);
darray_exit(&online_devices);
printbuf_exit(&err);
return ret;
}