The fiemap handler locks a file range that can have unflushed delalloc,
and after locking the range, it tries to attach to a running transaction.
If the running transaction started its commit, that is, it is in state
TRANS_STATE_COMMIT_START, and either the filesystem was mounted with the
flushoncommit option or the transaction is creating a snapshot for the
subvolume that contains the file that fiemap is operating on, we end up
deadlocking. This happens because fiemap is blocked on the transaction,
waiting for it to complete, and the transaction is waiting for the flushed
dealloc to complete, which requires locking the file range that the fiemap
task already locked. The following stack traces serve as an example of
when this deadlock happens:
(...)
[404571.515510] Workqueue: btrfs-endio-write btrfs_endio_write_helper [btrfs]
[404571.515956] Call Trace:
[404571.516360] ? __schedule+0x3ae/0x7b0
[404571.516730] schedule+0x3a/0xb0
[404571.517104] lock_extent_bits+0x1ec/0x2a0 [btrfs]
[404571.517465] ? remove_wait_queue+0x60/0x60
[404571.517832] btrfs_finish_ordered_io+0x292/0x800 [btrfs]
[404571.518202] normal_work_helper+0xea/0x530 [btrfs]
[404571.518566] process_one_work+0x21e/0x5c0
[404571.518990] worker_thread+0x4f/0x3b0
[404571.519413] ? process_one_work+0x5c0/0x5c0
[404571.519829] kthread+0x103/0x140
[404571.520191] ? kthread_create_worker_on_cpu+0x70/0x70
[404571.520565] ret_from_fork+0x3a/0x50
[404571.520915] kworker/u8:6 D 0 31651 2 0x80004000
[404571.521290] Workqueue: btrfs-flush_delalloc btrfs_flush_delalloc_helper [btrfs]
(...)
[404571.537000] fsstress D 0 13117 13115 0x00004000
[404571.537263] Call Trace:
[404571.537524] ? __schedule+0x3ae/0x7b0
[404571.537788] schedule+0x3a/0xb0
[404571.538066] wait_current_trans+0xc8/0x100 [btrfs]
[404571.538349] ? remove_wait_queue+0x60/0x60
[404571.538680] start_transaction+0x33c/0x500 [btrfs]
[404571.539076] btrfs_check_shared+0xa3/0x1f0 [btrfs]
[404571.539513] ? extent_fiemap+0x2ce/0x650 [btrfs]
[404571.539866] extent_fiemap+0x2ce/0x650 [btrfs]
[404571.540170] do_vfs_ioctl+0x526/0x6f0
[404571.540436] ksys_ioctl+0x70/0x80
[404571.540734] __x64_sys_ioctl+0x16/0x20
[404571.540997] do_syscall_64+0x60/0x1d0
[404571.541279] entry_SYSCALL_64_after_hwframe+0x49/0xbe
(...)
[404571.543729] btrfs D 0 14210 14208 0x00004000
[404571.544023] Call Trace:
[404571.544275] ? __schedule+0x3ae/0x7b0
[404571.544526] ? wait_for_completion+0x112/0x1a0
[404571.544795] schedule+0x3a/0xb0
[404571.545064] schedule_timeout+0x1ff/0x390
[404571.545351] ? lock_acquire+0xa6/0x190
[404571.545638] ? wait_for_completion+0x49/0x1a0
[404571.545890] ? wait_for_completion+0x112/0x1a0
[404571.546228] wait_for_completion+0x131/0x1a0
[404571.546503] ? wake_up_q+0x70/0x70
[404571.546775] btrfs_wait_ordered_extents+0x27c/0x400 [btrfs]
[404571.547159] btrfs_commit_transaction+0x3b0/0xae0 [btrfs]
[404571.547449] ? btrfs_mksubvol+0x4a4/0x640 [btrfs]
[404571.547703] ? remove_wait_queue+0x60/0x60
[404571.547969] btrfs_mksubvol+0x605/0x640 [btrfs]
[404571.548226] ? __sb_start_write+0xd4/0x1c0
[404571.548512] ? mnt_want_write_file+0x24/0x50
[404571.548789] btrfs_ioctl_snap_create_transid+0x169/0x1a0 [btrfs]
[404571.549048] btrfs_ioctl_snap_create_v2+0x11d/0x170 [btrfs]
[404571.549307] btrfs_ioctl+0x133f/0x3150 [btrfs]
[404571.549549] ? mem_cgroup_charge_statistics+0x4c/0xd0
[404571.549792] ? mem_cgroup_commit_charge+0x84/0x4b0
[404571.550064] ? __handle_mm_fault+0xe3e/0x11f0
[404571.550306] ? do_raw_spin_unlock+0x49/0xc0
[404571.550608] ? _raw_spin_unlock+0x24/0x30
[404571.550976] ? __handle_mm_fault+0xedf/0x11f0
[404571.551319] ? do_vfs_ioctl+0xa2/0x6f0
[404571.551659] ? btrfs_ioctl_get_supported_features+0x30/0x30 [btrfs]
[404571.552087] do_vfs_ioctl+0xa2/0x6f0
[404571.552355] ksys_ioctl+0x70/0x80
[404571.552621] __x64_sys_ioctl+0x16/0x20
[404571.552864] do_syscall_64+0x60/0x1d0
[404571.553104] entry_SYSCALL_64_after_hwframe+0x49/0xbe
(...)
If we were joining the transaction instead of attaching to it, we would
not risk a deadlock because a join only blocks if the transaction is in a
state greater then or equals to TRANS_STATE_COMMIT_DOING, and the delalloc
flush performed by a transaction is done before it reaches that state,
when it is in the state TRANS_STATE_COMMIT_START. However a transaction
join is intended for use cases where we do modify the filesystem, and
fiemap only needs to peek at delayed references from the current
transaction in order to determine if extents are shared, and, besides
that, when there is no current transaction or when it blocks to wait for
a current committing transaction to complete, it creates a new transaction
without reserving any space. Such unnecessary transactions, besides doing
unnecessary IO, can cause transaction aborts (-ENOSPC) and unnecessary
rotation of the precious backup roots.
So fix this by adding a new transaction join variant, named join_nostart,
which behaves like the regular join, but it does not create a transaction
when none currently exists or after waiting for a committing transaction
to complete.
Fixes: 03628cdbc6 ("Btrfs: do not start a transaction during fiemap")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_check_shared looks up parents of a given extent and uses ulists
for that. These are allocated and freed repeatedly. Preallocation in the
caller will avoid the overhead and also allow us to use the GFP_KERNEL
as it is happens before the extent locks are taken.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
During fiemap, for regular extents (non inline) we need to check if they
are shared and if they are, set the shared bit. Checking if an extent is
shared requires checking the delayed references of the currently running
transaction, since some reference might have not yet hit the extent tree
and be only in the in-memory delayed references.
However we were using a transaction join for this, which creates a new
transaction when there is no transaction currently running. That means
that two more potential failures can happen: creating the transaction and
committing it. Further, if no write activity is currently happening in the
system, and fiemap calls keep being done, we end up creating and
committing transactions that do nothing.
In some extreme cases this can result in the commit of the transaction
created by fiemap to fail with ENOSPC when updating the root item of a
subvolume tree because a join does not reserve any space, leading to a
trace like the following:
heisenberg kernel: ------------[ cut here ]------------
heisenberg kernel: BTRFS: Transaction aborted (error -28)
heisenberg kernel: WARNING: CPU: 0 PID: 7137 at fs/btrfs/root-tree.c:136 btrfs_update_root+0x22b/0x320 [btrfs]
(...)
heisenberg kernel: CPU: 0 PID: 7137 Comm: btrfs-transacti Not tainted 4.19.0-4-amd64 #1 Debian 4.19.28-2
heisenberg kernel: Hardware name: FUJITSU LIFEBOOK U757/FJNB2A5, BIOS Version 1.21 03/19/2018
heisenberg kernel: RIP: 0010:btrfs_update_root+0x22b/0x320 [btrfs]
(...)
heisenberg kernel: RSP: 0018:ffffb5448828bd40 EFLAGS: 00010286
heisenberg kernel: RAX: 0000000000000000 RBX: ffff8ed56bccef50 RCX: 0000000000000006
heisenberg kernel: RDX: 0000000000000007 RSI: 0000000000000092 RDI: ffff8ed6bda166a0
heisenberg kernel: RBP: 00000000ffffffe4 R08: 00000000000003df R09: 0000000000000007
heisenberg kernel: R10: 0000000000000000 R11: 0000000000000001 R12: ffff8ed63396a078
heisenberg kernel: R13: ffff8ed092d7c800 R14: ffff8ed64f5db028 R15: ffff8ed6bd03d068
heisenberg kernel: FS: 0000000000000000(0000) GS:ffff8ed6bda00000(0000) knlGS:0000000000000000
heisenberg kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
heisenberg kernel: CR2: 00007f46f75f8000 CR3: 0000000310a0a002 CR4: 00000000003606f0
heisenberg kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
heisenberg kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
heisenberg kernel: Call Trace:
heisenberg kernel: commit_fs_roots+0x166/0x1d0 [btrfs]
heisenberg kernel: ? _cond_resched+0x15/0x30
heisenberg kernel: ? btrfs_run_delayed_refs+0xac/0x180 [btrfs]
heisenberg kernel: btrfs_commit_transaction+0x2bd/0x870 [btrfs]
heisenberg kernel: ? start_transaction+0x9d/0x3f0 [btrfs]
heisenberg kernel: transaction_kthread+0x147/0x180 [btrfs]
heisenberg kernel: ? btrfs_cleanup_transaction+0x530/0x530 [btrfs]
heisenberg kernel: kthread+0x112/0x130
heisenberg kernel: ? kthread_bind+0x30/0x30
heisenberg kernel: ret_from_fork+0x35/0x40
heisenberg kernel: ---[ end trace 05de912e30e012d9 ]---
Since fiemap (and btrfs_check_shared()) is a read-only operation, do not do
a transaction join to avoid the overhead of creating a new transaction (if
there is currently no running transaction) and introducing a potential
point of failure when the new transaction gets committed, instead use a
transaction attach to grab a handle for the currently running transaction
if any.
Reported-by: Christoph Anton Mitterer <calestyo@scientia.net>
Link: https://lore.kernel.org/linux-btrfs/b2a668d7124f1d3e410367f587926f622b3f03a4.camel@scientia.net/
Fixes: afce772e87 ("btrfs: fix check_shared for fiemap ioctl")
CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When finding out which inodes have references on a particular extent, done
by backref.c:iterate_extent_inodes(), from the BTRFS_IOC_LOGICAL_INO (both
v1 and v2) ioctl and from scrub we use the transaction join API to grab a
reference on the currently running transaction, since in order to give
accurate results we need to inspect the delayed references of the currently
running transaction.
However, if there is currently no running transaction, the join operation
will create a new transaction. This is inefficient as the transaction will
eventually be committed, doing unnecessary IO and introducing a potential
point of failure that will lead to a transaction abort due to -ENOSPC, as
recently reported [1].
That's because the join, creates the transaction but does not reserve any
space, so when attempting to update the root item of the root passed to
btrfs_join_transaction(), during the transaction commit, we can end up
failling with -ENOSPC. Users of a join operation are supposed to actually
do some filesystem changes and reserve space by some means, which is not
the case of iterate_extent_inodes(), it is a read-only operation for all
contextes from which it is called.
The reported [1] -ENOSPC failure stack trace is the following:
heisenberg kernel: ------------[ cut here ]------------
heisenberg kernel: BTRFS: Transaction aborted (error -28)
heisenberg kernel: WARNING: CPU: 0 PID: 7137 at fs/btrfs/root-tree.c:136 btrfs_update_root+0x22b/0x320 [btrfs]
(...)
heisenberg kernel: CPU: 0 PID: 7137 Comm: btrfs-transacti Not tainted 4.19.0-4-amd64 #1 Debian 4.19.28-2
heisenberg kernel: Hardware name: FUJITSU LIFEBOOK U757/FJNB2A5, BIOS Version 1.21 03/19/2018
heisenberg kernel: RIP: 0010:btrfs_update_root+0x22b/0x320 [btrfs]
(...)
heisenberg kernel: RSP: 0018:ffffb5448828bd40 EFLAGS: 00010286
heisenberg kernel: RAX: 0000000000000000 RBX: ffff8ed56bccef50 RCX: 0000000000000006
heisenberg kernel: RDX: 0000000000000007 RSI: 0000000000000092 RDI: ffff8ed6bda166a0
heisenberg kernel: RBP: 00000000ffffffe4 R08: 00000000000003df R09: 0000000000000007
heisenberg kernel: R10: 0000000000000000 R11: 0000000000000001 R12: ffff8ed63396a078
heisenberg kernel: R13: ffff8ed092d7c800 R14: ffff8ed64f5db028 R15: ffff8ed6bd03d068
heisenberg kernel: FS: 0000000000000000(0000) GS:ffff8ed6bda00000(0000) knlGS:0000000000000000
heisenberg kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
heisenberg kernel: CR2: 00007f46f75f8000 CR3: 0000000310a0a002 CR4: 00000000003606f0
heisenberg kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
heisenberg kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
heisenberg kernel: Call Trace:
heisenberg kernel: commit_fs_roots+0x166/0x1d0 [btrfs]
heisenberg kernel: ? _cond_resched+0x15/0x30
heisenberg kernel: ? btrfs_run_delayed_refs+0xac/0x180 [btrfs]
heisenberg kernel: btrfs_commit_transaction+0x2bd/0x870 [btrfs]
heisenberg kernel: ? start_transaction+0x9d/0x3f0 [btrfs]
heisenberg kernel: transaction_kthread+0x147/0x180 [btrfs]
heisenberg kernel: ? btrfs_cleanup_transaction+0x530/0x530 [btrfs]
heisenberg kernel: kthread+0x112/0x130
heisenberg kernel: ? kthread_bind+0x30/0x30
heisenberg kernel: ret_from_fork+0x35/0x40
heisenberg kernel: ---[ end trace 05de912e30e012d9 ]---
So fix that by using the attach API, which does not create a transaction
when there is currently no running transaction.
[1] https://lore.kernel.org/linux-btrfs/b2a668d7124f1d3e410367f587926f622b3f03a4.camel@scientia.net/
Reported-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
BUG_ON(1) leads to bogus warnings from clang when
CONFIG_PROFILE_ANNOTATED_BRANCHES is set:
fs/btrfs/volumes.c:5041:3: error: variable 'max_chunk_size' is used uninitialized whenever 'if' condition is false
[-Werror,-Wsometimes-uninitialized]
BUG_ON(1);
^~~~~~~~~
include/asm-generic/bug.h:61:36: note: expanded from macro 'BUG_ON'
#define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
^~~~~~~~~~~~~~~~~~~
include/linux/compiler.h:48:23: note: expanded from macro 'unlikely'
# define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x)))
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fs/btrfs/volumes.c:5046:9: note: uninitialized use occurs here
max_chunk_size);
^~~~~~~~~~~~~~
include/linux/kernel.h:860:36: note: expanded from macro 'min'
#define min(x, y) __careful_cmp(x, y, <)
^
include/linux/kernel.h:853:17: note: expanded from macro '__careful_cmp'
__cmp_once(x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y), op))
^
include/linux/kernel.h:847:25: note: expanded from macro '__cmp_once'
typeof(y) unique_y = (y); \
^
fs/btrfs/volumes.c:5041:3: note: remove the 'if' if its condition is always true
BUG_ON(1);
^
include/asm-generic/bug.h:61:32: note: expanded from macro 'BUG_ON'
#define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
^
fs/btrfs/volumes.c:4993:20: note: initialize the variable 'max_chunk_size' to silence this warning
u64 max_chunk_size;
^
= 0
Change it to BUG() so clang can see that this code path can never
continue.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Qgroups will do the old roots lookup at delayed ref time, which could be
while walking down the extent root while running a delayed ref. This
should be fine, except we specifically lock eb's in the backref walking
code irrespective of path->skip_locking, which deadlocks the system.
Fix up the backref code to honor path->skip_locking, nobody will be
modifying the commit_root when we're searching so it's completely safe
to do.
This happens since fb235dc06f ("btrfs: qgroup: Move half of the qgroup
accounting time out of commit trans"), kernel may lockup with quota
enabled.
There is one backref trace triggered by snapshot dropping along with
write operation in the source subvolume. The example can be reliably
reproduced:
btrfs-cleaner D 0 4062 2 0x80000000
Call Trace:
schedule+0x32/0x90
btrfs_tree_read_lock+0x93/0x130 [btrfs]
find_parent_nodes+0x29b/0x1170 [btrfs]
btrfs_find_all_roots_safe+0xa8/0x120 [btrfs]
btrfs_find_all_roots+0x57/0x70 [btrfs]
btrfs_qgroup_trace_extent_post+0x37/0x70 [btrfs]
btrfs_qgroup_trace_leaf_items+0x10b/0x140 [btrfs]
btrfs_qgroup_trace_subtree+0xc8/0xe0 [btrfs]
do_walk_down+0x541/0x5e3 [btrfs]
walk_down_tree+0xab/0xe7 [btrfs]
btrfs_drop_snapshot+0x356/0x71a [btrfs]
btrfs_clean_one_deleted_snapshot+0xb8/0xf0 [btrfs]
cleaner_kthread+0x12b/0x160 [btrfs]
kthread+0x112/0x130
ret_from_fork+0x27/0x50
When dropping snapshots with qgroup enabled, we will trigger backref
walk.
However such backref walk at that timing is pretty dangerous, as if one
of the parent nodes get WRITE locked by other thread, we could cause a
dead lock.
For example:
FS 260 FS 261 (Dropped)
node A node B
/ \ / \
node C node D node E
/ \ / \ / \
leaf F|leaf G|leaf H|leaf I|leaf J|leaf K
The lock sequence would be:
Thread A (cleaner) | Thread B (other writer)
-----------------------------------------------------------------------
write_lock(B) |
write_lock(D) |
^^^ called by walk_down_tree() |
| write_lock(A)
| write_lock(D) << Stall
read_lock(H) << for backref walk |
read_lock(D) << lock owner is |
the same thread A |
so read lock is OK |
read_lock(A) << Stall |
So thread A hold write lock D, and needs read lock A to unlock.
While thread B holds write lock A, while needs lock D to unlock.
This will cause a deadlock.
This is not only limited to snapshot dropping case. As the backref
walk, even only happens on commit trees, is breaking the normal top-down
locking order, makes it deadlock prone.
Fixes: fb235dc06f ("btrfs: qgroup: Move half of the qgroup accounting time out of commit trans")
CC: stable@vger.kernel.org # 4.14+
Reported-and-tested-by: David Sterba <dsterba@suse.com>
Reported-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
[ rebase to latest branch and fix lock assert bug in btrfs/007 ]
Signed-off-by: Qu Wenruo <wqu@suse.com>
[ copy logs and deadlock analysis from Qu's patch ]
Signed-off-by: David Sterba <dsterba@suse.com>
We can use the right helper where the lock type is a fixed parameter.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
The typos accumulate over time so once in a while time they get fixed in
a large patch.
Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In iterate_inode_exrefs the eb is cloned via btrfs_clone_extent_buffer
which creates a private extent buffer with the dummy flag set and ref
count of 1. Then this buffer is locked for reading and its ref count is
incremented by 1. Finally it's fed to the passed iterate_irefs_t
function. The actual iterate call back is inode_to_path (coming from
paths_from_inode) which feeds the eb to btrfs_ref_to_path. In this final
function the passed eb is only read by first assigning it to the local
eb variable. This variable is only modified in the case another eb was
referenced from the passed path that is eb != eb_in check triggers.
Considering this there is no point in locking the cloned eb in
iterate_inode_refs since it's never being modified and is not published
anywhere. Furthermore the cloned eb is completely fine having its ref
count be 1.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In iterate_inode_refs the eb is cloned via btrfs_clone_extent_buffer
which creates a private extent buffer with the dummy flag set and ref
count of 1. Then this buffer is locked for reading and its ref count is
incremented by 1. Finally it's fed to the passed iterate_irefs_t
function. The actual iterate call back is inode_to_path (coming from
paths_from_inode) which feeds the eb to btrfs_ref_to_path. In this final
function the passed eb is only read by first assigning it to the local
eb variable. This variable is only modified in the case another eb was
referenced from the passed path that is eb != eb_in check triggers.
Considering this there is no point in locking the cloned eb in
iterate_inode_refs since it's never being modified and is not published
anywhere. Furthermore the cloned eb is completely fine having its ref
count be 1.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
rb_first_cached() trades an extra pointer "leftmost" for doing the same
job as rb_first() but in O(1).
While resolving indirect refs and missing refs, it always looks for the
first rb entry in a while loop, it's helpful to use rb_first_cached
instead.
For more details about the optimization see patch "Btrfs: delayed-refs:
use rb_first_cached for href_root".
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
rb_first_cached() trades an extra pointer "leftmost" for doing the same
job as rb_first() but in O(1).
Functions manipulating href->ref_tree need to get the first entry, this
converts href->ref_tree to use rb_first_cached().
For more details about the optimization see patch "Btrfs: delayed-refs:
use rb_first_cached for href_root".
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There are two members in struct btrfs_root which indicate root's
objectid: objectid and root_key.objectid.
They are both set to the same value in __setup_root():
static void __setup_root(struct btrfs_root *root,
struct btrfs_fs_info *fs_info,
u64 objectid)
{
...
root->objectid = objectid;
...
root->root_key.objectid = objecitd;
...
}
and not changed to other value after initialization.
grep in btrfs directory shows both are used in many places:
$ grep -rI "root->root_key.objectid" | wc -l
133
$ grep -rI "root->objectid" | wc -l
55
(4.17, inc. some noise)
It is confusing to have two similar variable names and it seems
that there is no rule about which should be used in a certain case.
Since ->root_key itself is needed for tree reloc tree, let's remove
'objecitd' member and unify code to use ->root_key.objectid in all places.
Signed-off-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Use ERR_CAST() instead of void * to make meaning clear.
Signed-off-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If type of extent_inline_ref found is not expected, filesystem may have
been corrupted, should return EUCLEAN instead of EINVAL.
Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Remove GPL boilerplate text (long, short, one-line) and keep the rest,
ie. personal, company or original source copyright statements. Add the
SPDX header.
Signed-off-by: David Sterba <dsterba@suse.com>
We have several reports about node pointer points to incorrect child
tree blocks, which could have even wrong owner and level but still with
valid generation and checksum.
Although btrfs check could handle it and print error message like:
leaf parent key incorrect 60670574592
Kernel doesn't have enough check on this type of corruption correctly.
At least add such check to read_tree_block() and btrfs_read_buffer(),
where we need two new parameters @level and @first_key to verify the
child tree block.
The new @level check is mandatory and all call sites are already
modified to extract expected level from its call chain.
While @first_key is optional, the following call sites are skipping such
check:
1) Root node/leaf
As ROOT_ITEM doesn't contain the first key, skip @first_key check.
2) Direct backref
Only parent bytenr and level is known and we need to resolve the key
all by ourselves, skip @first_key check.
Another note of this verification is, it needs extra info from nodeptr
or ROOT_ITEM, so it can't fit into current tree-checker framework, which
is limited to node/leaf boundary.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Added as part of 86d5f99442 ("btrfs: convert prelimary reference
tracking to use rbtrees") but never used. tmp_op_key essentially
subsumed that variable.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The __cold functions are placed to a special section, as they're
expected to be called rarely. This could help i-cache prefetches or help
compiler to decide which branches are more/less likely to be taken
without any other annotations needed.
Though we can't add more __exit annotations, it's still possible to add
__cold (that's also added with __exit). That way the following function
categories are tagged:
- printf wrappers, error messages
- exit helpers
Signed-off-by: David Sterba <dsterba@suse.com>
This patch addresses an issue that causes fiemap to falsely
report a shared extent. The test case is as follows:
xfs_io -f -d -c "pwrite -b 16k 0 64k" -c "fiemap -v" /media/scratch/file5
sync
xfs_io -c "fiemap -v" /media/scratch/file5
which gives the resulting output:
wrote 65536/65536 bytes at offset 0
64 KiB, 4 ops; 0.0000 sec (121.359 MiB/sec and 7766.9903 ops/sec)
/media/scratch/file5:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..127]: 24576..24703 128 0x2001
/media/scratch/file5:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..127]: 24576..24703 128 0x1
This is because btrfs_check_shared calls find_parent_nodes
repeatedly in a loop, passing a share_check struct to report
the count of shared extent. But btrfs_check_shared does not
re-initialize the count value to zero for subsequent calls
from the loop, resulting in a false share count value. This
is a regressive behavior from 4.13.
With proper re-initialization the test result is as follows:
wrote 65536/65536 bytes at offset 0
64 KiB, 4 ops; 0.0000 sec (110.035 MiB/sec and 7042.2535 ops/sec)
/media/scratch/file5:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..127]: 24576..24703 128 0x1
/media/scratch/file5:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..127]: 24576..24703 128 0x1
which corrects the regression.
Fixes: 3ec4d3238a ("btrfs: allow backref search checks for shared extents")
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
[ add text from cover letter to changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
Until v4.14, this warning was very infrequent:
WARNING: CPU: 3 PID: 18172 at fs/btrfs/backref.c:1391 find_parent_nodes+0xc41/0x14e0
Modules linked in: [...]
CPU: 3 PID: 18172 Comm: bees Tainted: G D W L 4.11.9-zb64+ #1
Hardware name: System manufacturer System Product Name/M5A78L-M/USB3, BIOS 2101 12/02/2014
Call Trace:
dump_stack+0x85/0xc2
__warn+0xd1/0xf0
warn_slowpath_null+0x1d/0x20
find_parent_nodes+0xc41/0x14e0
__btrfs_find_all_roots+0xad/0x120
? extent_same_check_offsets+0x70/0x70
iterate_extent_inodes+0x168/0x300
iterate_inodes_from_logical+0x87/0xb0
? iterate_inodes_from_logical+0x87/0xb0
? extent_same_check_offsets+0x70/0x70
btrfs_ioctl+0x8ac/0x2820
? lock_acquire+0xc2/0x200
do_vfs_ioctl+0x91/0x700
? __fget+0x112/0x200
SyS_ioctl+0x79/0x90
entry_SYSCALL_64_fastpath+0x23/0xc6
? trace_hardirqs_off_caller+0x1f/0x140
Starting with v4.14 (specifically 86d5f99442 ("btrfs: convert prelimary
reference tracking to use rbtrees")) the WARN_ON occurs three orders of
magnitude more frequently--almost once per second while running workloads
like bees.
Replace the WARN_ON() with a comment rationale for its removal.
The rationale is paraphrased from an explanation by Edmund Nadolski
<enadolski@suse.de> on the linux-btrfs mailing list.
Fixes: 8da6d5815c ("Btrfs: added btrfs_find_all_roots()")
Signed-off-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Reviewed-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The function update_share_count is local to the source and does
not need to be in global scope, so make it static.
Cleans up sparse warning:
fs/btrfs/backref.c:219:6: warning: symbol 'update_share_count' was not
declared. Should it be static?
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If we get a significant amount of delayed refs for a single block (think
modifying multiple snapshots) we can end up spending an ungodly amount
of time looping through all of the entries trying to see if they can be
merged. This is because we only add them to a list, so we have O(2n)
for every ref head. This doesn't make any sense as we likely have refs
for different roots, and so they cannot be merged. Tracking in a tree
will allow us to break as soon as we hit an entry that doesn't match,
making our worst case O(n).
With this we can also merge entries more easily. Before we had to hope
that matching refs were on the ends of our list, but with the tree we
can search down to exact matches and merge them at insert time.
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The LOGICAL_INO ioctl provides a backward mapping from extent bytenr and
offset (encoded as a single logical address) to a list of extent refs.
LOGICAL_INO complements TREE_SEARCH, which provides the forward mapping
(extent ref -> extent bytenr and offset, or logical address). These are
useful capabilities for programs that manipulate extents and extent
references from userspace (e.g. dedup and defrag utilities).
When the extents are uncompressed (and not encrypted and not other),
check_extent_in_eb performs filtering of the extent refs to remove any
extent refs which do not contain the same extent offset as the 'logical'
parameter's extent offset. This prevents LOGICAL_INO from returning
references to more than a single block.
To find the set of extent references to an uncompressed extent from [a, b),
userspace has to run a loop like this pseudocode:
for (i = a; i < b; ++i)
extent_ref_set += LOGICAL_INO(i);
At each iteration of the loop (up to 32768 iterations for a 128M extent),
data we are interested in is collected in the kernel, then deleted by
the filter in check_extent_in_eb.
When the extents are compressed (or encrypted or other), the 'logical'
parameter must be an extent bytenr (the 'a' parameter in the loop).
No filtering by extent offset is done (or possible?) so the result is
the complete set of extent refs for the entire extent. This removes
the need for the loop, since we get all the extent refs in one call.
Add an 'ignore_offset' argument to iterate_inodes_from_logical,
[...several levels of function call graph...], and check_extent_in_eb, so
that we can disable the extent offset filtering for uncompressed extents.
This flag can be set by an improved version of the LOGICAL_INO ioctl to
get either behavior as desired.
There is no functional change in this patch. The new flag is always
false.
Signed-off-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Reviewed-by: David Sterba <dsterba@suse.com>
[ minor coding style fixes ]
Signed-off-by: David Sterba <dsterba@suse.com>
This is just excessive information in the ref_head, and makes the code
complicated. It is a relic from when we had the heads and the refs in
the same tree, which is no longer the case. With this removal I've
cleaned up a bunch of the cruft around this old assumption as well.
Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Since we have a helper which can do sanity check, this converts all
btrfs_extent_inline_ref_type to it.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Repeating the same computation in multiple places is not
necessary.
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When called with a struct share_check, find_parent_nodes()
will detect a shared extent and immediately return with
BACKREF_SHARED_FOUND.
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Since backref resolution is CPU-intensive, the cond_resched calls
should help alleviate soft lockup occurences.
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This patch adds a tracepoint event for prelim_ref insertion and
merging. For each, the ref being inserted or merged and the count
of tree nodes is issued.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This patch adds counters to each of the rbtrees so that we can tell
how large they are growing for a given workload. These counters
will be exported by tracepoints in the next patch.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
It's been known for a while that the use of multiple lists
that are periodically merged was an algorithmic problem within
btrfs. There are several workloads that don't complete in any
reasonable amount of time (e.g. btrfs/130) and others that cause
soft lockups.
The solution is to use a set of rbtrees that do insertion merging
for both indirect and direct refs, with the former converting
refs into the latter. The result is a btrfs/130 workload that
used to take several hours now takes about half of that. This
runtime still isn't acceptable and a future patch will address that
by moving the rbtrees higher in the stack so the lookups can be
shared across multiple calls to find_parent_nodes.
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Commit afce772e87 ("btrfs: fix check_shared for fiemap ioctl") added
the ref_tree code in backref.c to reduce backref searching for
shared extents under the FIEMAP ioctl. This code will not be
compatible with the upcoming rbtree changes for improved backref
searching, so this patch removes the ref_tree code. The rbtree
changes will provide the equivalent functionality for FIEMAP.
The above commit also introduced transaction semantics around calls to
btrfs_check_shared() in order to accurately account for delayed refs.
This functionality needs to be retained, so a complete revert of the
above commit is not desirable. This patch therefore removes the
ref_tree portion of the commit as above, however it does not remove
the transaction portion.
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Commit afce772e87 ("btrfs: fix check_shared for fiemap ioctl") added
transaction semantics around calls to btrfs_check_shared() in order to
provide accurate accounting of delayed refs. The transaction management
should be done inside btrfs_check_shared(), so that callers do not need
to manage transactions individually.
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We typically use __ to indicate a helper routine that shouldn't be
called directly without understanding the proper context required
to do so. We use static functions to indicate that a function is
private to a particular C file. The backref code uses static
function and __ prefixes on nearly everything, which makes the code
difficult to read and establishes a pattern for future code that
shouldn't be followed. This patch drops all the unnecessary prefixes.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Replacing the double cast and ternary conditional with a helper makes
the code easier on the eyes.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Now that init_ipath is called either from a safe context or with
memalloc_nofs protection, we can switch to GFP_KERNEL allocations in
init_path and init_data_container.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Define the SEQ_LAST macro to replace (u64)-1 in places where said
value triggers a special-case ref search behavior.
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
Reviewed-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Replace hardcoded numeric values for __merge_refs 'mode' argument
with descriptive constants.
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
Reviewed-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
All we need is @delayed_refs, all callers have get it ahead of calling
btrfs_find_delayed_ref_head since lock needs to be acquired firstly,
there is no reason to deference it again inside the function.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Now we only use the root parameter to print the root objectid in
a tracepoint. We can use the root parameter from the transaction
handle for that. It's also used to join the transaction with
async commits, so we remove the comment that it's just for checking.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There are loads of functions in btrfs that accept a root parameter
but only use it to obtain an fs_info pointer. Let's convert those to
just accept an fs_info pointer directly.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We track the node sizes per-root, but they never vary from the values
in the superblock. This patch messes with the 80-column style a bit,
but subsequent patches to factor out root->fs_info into a convenience
variable fix it up again.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For many printks, we want to know which file system issued the message.
This patch converts most pr_* calls to use the btrfs_* versions instead.
In some cases, this means adding plumbing to allow call sites access to
an fs_info pointer.
fs/btrfs/check-integrity.c is left alone for another day.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
CodingStyle chapter 2:
"[...] never break user-visible strings such as printk messages,
because that breaks the ability to grep for them."
This patch unsplits user-visible strings.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Only in the case of different root_id or different object_id, check_shared
identified extent as the shared. However, If a extent was referred by
different offset of same file, it should also be identified as shared.
In addition, check_shared's loop scale is at least n^3, so if a extent
has too many references, even causes soft hang up.
First, add all delayed_ref to the ref_tree and calculate the unqiue_refs,
if the unique_refs is greater than one, return BACKREF_FOUND_SHARED.
Then individually add the on-disk reference(inline/keyed) to the ref_tree
and calculate the unique_refs of the ref_tree to check if the unique_refs
is greater than one.Because once there are two references to return
SHARED, so the time complexity is close to the constant.
Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When over 1000 file extents refers to one extent, find_parent_nodes()
will be obviously slow, due to the O(n^2)~O(n^3) loops inside
__merge_refs().
The following ftrace shows the cubic growth of execution time:
256 refs
5) + 91.768 us | __add_keyed_refs.isra.12 [btrfs]();
5) 1.447 us | __add_missing_keys.isra.13 [btrfs]();
5) ! 114.544 us | __merge_refs [btrfs]();
5) ! 136.399 us | __merge_refs [btrfs]();
512 refs
6) ! 279.859 us | __add_keyed_refs.isra.12 [btrfs]();
6) 3.164 us | __add_missing_keys.isra.13 [btrfs]();
6) ! 442.498 us | __merge_refs [btrfs]();
6) # 2091.073 us | __merge_refs [btrfs]();
and 1024 refs
7) ! 368.683 us | __add_keyed_refs.isra.12 [btrfs]();
7) 4.810 us | __add_missing_keys.isra.13 [btrfs]();
7) # 2043.428 us | __merge_refs [btrfs]();
7) * 18964.23 us | __merge_refs [btrfs]();
And sort them into the following char:
(Unit: us)
------------------------------------------------------------------------
Trace function | 256 ref | 512 refs | 1024 refs |
------------------------------------------------------------------------
__add_keyed_refs | 91 | 249 | 368 |
__add_missing_keys | 1 | 3 | 4 |
__merge_refs 1st call | 114 | 442 | 2043 |
__merge_refs 2nd call | 136 | 2091 | 18964 |
------------------------------------------------------------------------
We can see the that __add_keyed_refs() grows almost in linear behavior.
And __add_missing_keys() in this case doesn't change much or takes much
time.
While for the 1st __merge_refs() it's square growth
for the 2nd __merge_refs() call it's cubic growth.
It's no doubt that merge_refs() will take a long long time to execute if
the number of refs continues its grows.
So add a cond_resced() into the loop of __merge_refs().
Although this will solve the problem of soft lockup, we need to use the
new rb_tree based structure introduced by Lu Fengqi to really solve the
long execution time.
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
