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When a bad checksum is found and if the filesystem has a mirror of the
damaged data, we read the correct data from the mirror and writes it to
damaged blocks. This however, violates the sequential write constraints
of a zoned block device.
We can consider three methods to repair an IO failure in zoned filesystems:
(1) Reset and rewrite the damaged zone
(2) Allocate new device extent and replace the damaged device extent to
the new extent
(3) Relocate the corresponding block group
Method (1) is most similar to a behavior done with regular devices.
However, it also wipes non-damaged data in the same device extent, and
so it unnecessary degrades non-damaged data.
Method (2) is much like device replacing but done in the same device. It
is safe because it keeps the device extent until the replacing finish.
However, extending device replacing is non-trivial. It assumes
"src_dev->physical == dst_dev->physical". Also, the extent mapping
replacing function should be extended to support replacing device extent
position in one device.
Method (3) invokes relocation of the damaged block group and is
straightforward to implement. It relocates all the mirrored device
extents, so it potentially is a more costly operation than method (1) or
(2). But it relocates only used extents which reduce the total IO size.
Let's apply method (3) for now. In the future, we can extend device-replace
and apply method (2).
For protecting a block group gets relocated multiple time with multiple
IO errors, this commit introduces "relocating_repair" bit to show it's
now relocating to repair IO failures. Also it uses a new kthread
"btrfs-relocating-repair", not to block IO path with relocating process.
This commit also supports repairing in the scrub process.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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This is 4/4 patch to implement device-replace on zoned filesystems.
Even after the copying is done, the write pointers of the source device
and the destination device may not be synchronized. For example, when
the last allocated extent is freed before device-replace process, the
extent is not copied, leaving a hole there.
Synchronize the write pointers by writing zeroes to the destination
device.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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This is 3/4 patch to implement device-replace on zoned filesystems.
This commit implements copying. To do this, it tracks the write pointer
during the device replace process. As device-replace's copy process is
smart enough to only copy used extents on the source device, we have to
fill the gap to honor the sequential write requirement in the target
device.
The device-replace process on zoned filesystems must copy or clone all
the extents in the source device exactly once. So, we need to ensure
allocations started just before the dev-replace process to have their
corresponding extent information in the B-trees.
finish_extent_writes_for_zoned() implements that functionality, which
basically is the removed code in the commit 042528f8d840 ("Btrfs: fix
block group remaining RO forever after error during device replace").
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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This is the 1/4 patch to support device-replace on zoned filesystems.
We have two types of IOs during the device replace process. One is an IO
to "copy" (by the scrub functions) all the device extents from the source
device to the destination device. The other one is an IO to "clone" (by
handle_ops_on_dev_replace()) new incoming write IOs from users to the
source device into the target device.
Cloning incoming IOs can break the sequential write rule in on target
device. When a write is mapped in the middle of a block group, the IO is
directed to the middle of a target device zone, which breaks the
sequential write requirement.
However, the cloning function cannot be disabled since incoming IOs
targeting already copied device extents must be cloned so that the IO is
executed on the target device.
We cannot use dev_replace->cursor_{left,right} to determine whether a bio
is going to a not yet copied region. Since we have a time gap between
finishing btrfs_scrub_dev() and rewriting the mapping tree in
btrfs_dev_replace_finishing(), we can have a newly allocated device extent
which is never cloned nor copied.
So the point is to copy only already existing device extents. This patch
introduces mark_block_group_to_copy() to mark existing block groups as a
target of copying. Then, handle_ops_on_dev_replace() and dev-replace can
check the flag to do their job.
Also, btrfs_finish_block_group_to_copy() will check if the copied stripe
is the last stripe in the block group. With the last stripe copied,
the to_copy flag is finally disabled. Afterwards we can safely clone
incoming IOs on this block group.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Since btrfs scrub is utilizing its own infrastructure to submit
read/write, scrub is independent from all other routines.
This brings one very neat feature, allow us to read 4K data into offset
0 of a 64K page. So is the writeback routine.
This makes scrub on subpage sector size much easier to implement, and
thanks to previous commits which just changed the implementation to
always do scrub based on sector size, now scrub can handle subpage
filesystem without any problem.
This patch will just remove the restriction on
(sectorsize != PAGE_SIZE), to make scrub finally work on subpage
filesystems.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Btrfs scrub is more flexible than buffered data write path, as we can
read an unaligned subpage data into page offset 0.
This ability makes subpage support much easier, we just need to check
each scrub_page::page_len and ensure we only calculate hash for [0,
page_len) of a page.
There is a small thing to notice: for subpage case, we still do sector
by sector scrub. This means we will submit a read bio for each sector
to scrub, resulting in the same amount of read bios, just like on the 4K
page systems.
This behavior can be considered as a good thing, if we want everything
to be the same as 4K page systems. But this also means, we're wasting
the possibility to submit larger bio using 64K page size. This is
another problem to consider in the future.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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To support subpage tree block scrub, scrub_checksum_tree_block() only
needs to learn 2 new tricks:
- Follow sector size
Now scrub_page only represents one sector, we need to follow it
properly.
- Run checksum on all sectors
Since scrub_page only represents one sector, we need to run checksum
on all sectors, not only (nodesize >> PAGE_SIZE).
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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For scrub_pages() and scrub_pages_for_parity(), we currently allocate
one scrub_page structure for one page.
This is fine if we only read/write one sector one time. But for cases
like scrubbing RAID56, we need to read/write the full stripe, which is
in 64K size for now.
For subpage size, we will submit the read in just one page, which is
normally a good thing, but for RAID56 case, it only expects to see one
sector, not the full stripe in its endio function.
This could lead to wrong parity checksum for RAID56 on subpage.
To make the existing code work well for subpage case, here we take a
shortcut by always allocating a full page for one sector.
This should provide the base to make RAID56 work for subpage case.
The cost is pretty obvious now, for one RAID56 stripe now we always need
16 pages. For support subpage situation (64K page size, 4K sector size),
this means we need full one megabyte to scrub just one RAID56 stripe.
And for data scrub, each 4K sector will also need one 64K page.
This is mostly just a workaround, the proper fix for this is a much
larger project, using scrub_block to replace scrub_page, and allow
scrub_block to handle multi pages, csums, and csum_bitmap to avoid
allocating one page for each sector.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Btrfs on-disk format chose to use u64 for almost everything, but there
are a other restrictions that won't let us use more than u32 for things
like extent length (the maximum length is 128MiB for non-hole extents),
or stripe length (we have device number limit).
This means if we don't have extra handling to convert u64 to u32, we
will always have some questionable operations like
"u32 = u64 >> sectorsize_bits" in the code.
This patch will try to address the problem by reducing the width for the
following members/parameters:
- scrub_parity::stripe_len
- @len of scrub_pages()
- @extent_len of scrub_remap_extent()
- @len of scrub_parity_mark_sectors_error()
- @len of scrub_parity_mark_sectors_data()
- @len of scrub_extent()
- @len of scrub_pages_for_parity()
- @len of scrub_extent_for_parity()
For members extracted from on-disk structure, like map->stripe_len, they
will be kept as is. Since that modification would require on-disk format
change.
There will be cases like "u32 = u64 - u64" or "u32 = u64", for such call
sites, extra ASSERT() is added to be extra safe for debug builds.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Superblock (and its copies) is the only data structure in btrfs which
has a fixed location on a device. Since we cannot overwrite in a
sequential write required zone, we cannot place superblock in the zone.
One easy solution is limiting superblock and copies to be placed only in
conventional zones. However, this method has two downsides: one is
reduced number of superblock copies. The location of the second copy of
superblock is 256GB, which is in a sequential write required zone on
typical devices in the market today. So, the number of superblock and
copies is limited to be two. Second downside is that we cannot support
devices which have no conventional zones at all.
To solve these two problems, we employ superblock log writing. It uses
two adjacent zones as a circular buffer to write updated superblocks.
Once the first zone is filled up, start writing into the second one.
Then, when both zones are filled up and before starting to write to the
first zone again, it reset the first zone.
We can determine the position of the latest superblock by reading write
pointer information from a device. One corner case is when both zones
are full. For this situation, we read out the last superblock of each
zone, and compare them to determine which zone is older.
The following zones are reserved as the circular buffer on ZONED btrfs.
- The primary superblock: zones 0 and 1
- The first copy: zones 16 and 17
- The second copy: zones 1024 or zone at 256GB which is minimum, and
next to it
If these reserved zones are conventional, superblock is written fixed at
the start of the zone without logging.
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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That anonymous structure serve no special purpose, just replace it with
regular members.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Commit 343694eee8d8 ("btrfs: switch seed device to list api"), missed to
check if the parameter seed is true in the function btrfs_find_device().
This tells it whether to traverse the seed device list or not.
After this commit, the argument is unused and can be removed.
In device_list_add() it's not necessary because fs_devices always points
to the device's fs_devices. So with the devid+uuid matching, it will
find the right device and return, thus not needing to traverse seed
devices.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Function scrub_find_csum() is to locate the csum for bytenr @logical
from sctx->csum_list.
However it lacks a lot of comments to explain things like how the
csum_list is organized and why we need to drop csum range which is
before us.
Refactor the function by:
- Add more comments explaining the behavior
- Add comment explaining why we need to drop the csum range
- Put the csum copy in the main loop
This is mostly for the incoming patches to make scrub_find_csum() able
to find multiple checksums.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The @force parameter for scrub_pages() is to indicate whether we want to
force bio submission. Currently it's only used for the super block,
and it can be easily determined by the @flags, so we can remove the
parameter.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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There are several call sites where we declare something like
"struct scrub_page *page".
This is confusing as we also use regular page in this code,
rename it to 'spage' where applicable.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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The context structure unnecessarily stores copy of the checksum size,
that can be now easily obtained from fs_info.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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btrfs_get_16 shows up in the system performance profiles (helper to read
16bit values from on-disk structures). This is partially because of the
checksum size that's frequently read along with data reads/writes, other
u16 uses are from item size or directory entries.
Replace all calls to btrfs_super_csum_size by the cached value from
fs_info.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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We do a lot of calculations where we divide or multiply by sectorsize.
We also know and make sure that sectorsize is a power of two, so this
means all divisions can be turned to shifts and avoid eg. expensive
u64/u32 divisions.
The type is u32 as it's more register friendly on x86_64 compared to u8
and the resulting assembly is smaller (movzbl vs movl).
There's also superblock s_blocksize_bits but it's usually one more
pointer dereference farther than fs_info.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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When scrubbing a stripe of a block group we always start readahead for the
checksums btree and wait for it to complete, however when the blockgroup is
not a data block group (or a mixed block group) it is a waste of time to do
it, since there are no checksums for metadata extents in that btree.
So skip that when the block group does not have the data flag set, saving
some time doing memory allocations, queueing a job in the readahead work
queue, waiting for it to complete and potentially avoiding some IO as well
(when csum tree extents are not in memory already).
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Based on user feedback update the message printed when scrub fails to
start due to write requirements. To make a distinction add a device id
to the messages.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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There's already defined _rs within ctree.h:btrfs_printk_ratelimited,
local variables should not use _ to avoid such name clashes with
macro-local variables.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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I got the following lockdep splat while testing:
======================================================
WARNING: possible circular locking dependency detected
5.8.0-rc7-00172-g021118712e59 #932 Not tainted
------------------------------------------------------
btrfs/229626 is trying to acquire lock:
ffffffff828513f0 (cpu_hotplug_lock){++++}-{0:0}, at: alloc_workqueue+0x378/0x450
but task is already holding lock:
ffff889dd3889518 (&fs_info->scrub_lock){+.+.}-{3:3}, at: btrfs_scrub_dev+0x11c/0x630
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #7 (&fs_info->scrub_lock){+.+.}-{3:3}:
__mutex_lock+0x9f/0x930
btrfs_scrub_dev+0x11c/0x630
btrfs_dev_replace_by_ioctl.cold.21+0x10a/0x1d4
btrfs_ioctl+0x2799/0x30a0
ksys_ioctl+0x83/0xc0
__x64_sys_ioctl+0x16/0x20
do_syscall_64+0x50/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xa9
-> #6 (&fs_devs->device_list_mutex){+.+.}-{3:3}:
__mutex_lock+0x9f/0x930
btrfs_run_dev_stats+0x49/0x480
commit_cowonly_roots+0xb5/0x2a0
btrfs_commit_transaction+0x516/0xa60
sync_filesystem+0x6b/0x90
generic_shutdown_super+0x22/0x100
kill_anon_super+0xe/0x30
btrfs_kill_super+0x12/0x20
deactivate_locked_super+0x29/0x60
cleanup_mnt+0xb8/0x140
task_work_run+0x6d/0xb0
__prepare_exit_to_usermode+0x1cc/0x1e0
do_syscall_64+0x5c/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xa9
-> #5 (&fs_info->tree_log_mutex){+.+.}-{3:3}:
__mutex_lock+0x9f/0x930
btrfs_commit_transaction+0x4bb/0xa60
sync_filesystem+0x6b/0x90
generic_shutdown_super+0x22/0x100
kill_anon_super+0xe/0x30
btrfs_kill_super+0x12/0x20
deactivate_locked_super+0x29/0x60
cleanup_mnt+0xb8/0x140
task_work_run+0x6d/0xb0
__prepare_exit_to_usermode+0x1cc/0x1e0
do_syscall_64+0x5c/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xa9
-> #4 (&fs_info->reloc_mutex){+.+.}-{3:3}:
__mutex_lock+0x9f/0x930
btrfs_record_root_in_trans+0x43/0x70
start_transaction+0xd1/0x5d0
btrfs_dirty_inode+0x42/0xd0
touch_atime+0xa1/0xd0
btrfs_file_mmap+0x3f/0x60
mmap_region+0x3a4/0x640
do_mmap+0x376/0x580
vm_mmap_pgoff+0xd5/0x120
ksys_mmap_pgoff+0x193/0x230
do_syscall_64+0x50/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xa9
-> #3 (&mm->mmap_lock#2){++++}-{3:3}:
__might_fault+0x68/0x90
_copy_to_user+0x1e/0x80
perf_read+0x141/0x2c0
vfs_read+0xad/0x1b0
ksys_read+0x5f/0xe0
do_syscall_64+0x50/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xa9
-> #2 (&cpuctx_mutex){+.+.}-{3:3}:
__mutex_lock+0x9f/0x930
perf_event_init_cpu+0x88/0x150
perf_event_init+0x1db/0x20b
start_kernel+0x3ae/0x53c
secondary_startup_64+0xa4/0xb0
-> #1 (pmus_lock){+.+.}-{3:3}:
__mutex_lock+0x9f/0x930
perf_event_init_cpu+0x4f/0x150
cpuhp_invoke_callback+0xb1/0x900
_cpu_up.constprop.26+0x9f/0x130
cpu_up+0x7b/0xc0
bringup_nonboot_cpus+0x4f/0x60
smp_init+0x26/0x71
kernel_init_freeable+0x110/0x258
kernel_init+0xa/0x103
ret_from_fork+0x1f/0x30
-> #0 (cpu_hotplug_lock){++++}-{0:0}:
__lock_acquire+0x1272/0x2310
lock_acquire+0x9e/0x360
cpus_read_lock+0x39/0xb0
alloc_workqueue+0x378/0x450
__btrfs_alloc_workqueue+0x15d/0x200
btrfs_alloc_workqueue+0x51/0x160
scrub_workers_get+0x5a/0x170
btrfs_scrub_dev+0x18c/0x630
btrfs_dev_replace_by_ioctl.cold.21+0x10a/0x1d4
btrfs_ioctl+0x2799/0x30a0
ksys_ioctl+0x83/0xc0
__x64_sys_ioctl+0x16/0x20
do_syscall_64+0x50/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xa9
other info that might help us debug this:
Chain exists of:
cpu_hotplug_lock --> &fs_devs->device_list_mutex --> &fs_info->scrub_lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&fs_info->scrub_lock);
lock(&fs_devs->device_list_mutex);
lock(&fs_info->scrub_lock);
lock(cpu_hotplug_lock);
*** DEADLOCK ***
2 locks held by btrfs/229626:
#0: ffff88bfe8bb86e0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: btrfs_scrub_dev+0xbd/0x630
#1: ffff889dd3889518 (&fs_info->scrub_lock){+.+.}-{3:3}, at: btrfs_scrub_dev+0x11c/0x630
stack backtrace:
CPU: 15 PID: 229626 Comm: btrfs Kdump: loaded Not tainted 5.8.0-rc7-00172-g021118712e59 #932
Hardware name: Quanta Tioga Pass Single Side 01-0030993006/Tioga Pass Single Side, BIOS F08_3A18 12/20/2018
Call Trace:
dump_stack+0x78/0xa0
check_noncircular+0x165/0x180
__lock_acquire+0x1272/0x2310
lock_acquire+0x9e/0x360
? alloc_workqueue+0x378/0x450
cpus_read_lock+0x39/0xb0
? alloc_workqueue+0x378/0x450
alloc_workqueue+0x378/0x450
? rcu_read_lock_sched_held+0x52/0x80
__btrfs_alloc_workqueue+0x15d/0x200
btrfs_alloc_workqueue+0x51/0x160
scrub_workers_get+0x5a/0x170
btrfs_scrub_dev+0x18c/0x630
? start_transaction+0xd1/0x5d0
btrfs_dev_replace_by_ioctl.cold.21+0x10a/0x1d4
btrfs_ioctl+0x2799/0x30a0
? do_sigaction+0x102/0x250
? lockdep_hardirqs_on_prepare+0xca/0x160
? _raw_spin_unlock_irq+0x24/0x30
? trace_hardirqs_on+0x1c/0xe0
? _raw_spin_unlock_irq+0x24/0x30
? do_sigaction+0x102/0x250
? ksys_ioctl+0x83/0xc0
ksys_ioctl+0x83/0xc0
__x64_sys_ioctl+0x16/0x20
do_syscall_64+0x50/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xa9
This happens because we're allocating the scrub workqueues under the
scrub and device list mutex, which brings in a whole host of other
dependencies.
Because the work queue allocation is done with GFP_KERNEL, it can
trigger reclaim, which can lead to a transaction commit, which in turns
needs the device_list_mutex, it can lead to a deadlock. A different
problem for which this fix is a solution.
Fix this by moving the actual allocation outside of the
scrub lock, and then only take the lock once we're ready to actually
assign them to the fs_info. We'll now have to cleanup the workqueues in
a few more places, so I've added a helper to do the refcount dance to
safely free the workqueues.
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Eric reported seeing this message while running generic/475
BTRFS: error (device dm-3) in btrfs_sync_log:3084: errno=-117 Filesystem corrupted
Full stack trace:
BTRFS: error (device dm-0) in btrfs_commit_transaction:2323: errno=-5 IO failure (Error while writing out transaction)
BTRFS info (device dm-0): forced readonly
BTRFS warning (device dm-0): Skipping commit of aborted transaction.
------------[ cut here ]------------
BTRFS: error (device dm-0) in cleanup_transaction:1894: errno=-5 IO failure
BTRFS: Transaction aborted (error -117)
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c6480 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c6488 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c6490 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c6498 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c64a0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c64a8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c64b0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c64b8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c64c0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3572 rw 0,0 sector 0x1b85e8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3572 rw 0,0 sector 0x1b85f0 len 4096 err no 10
WARNING: CPU: 3 PID: 23985 at fs/btrfs/tree-log.c:3084 btrfs_sync_log+0xbc8/0xd60 [btrfs]
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d4288 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d4290 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d4298 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42a0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42a8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42b0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42b8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42c0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42c8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42d0 len 4096 err no 10
CPU: 3 PID: 23985 Comm: fsstress Tainted: G W L 5.8.0-rc4-default+ #1181
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
RIP: 0010:btrfs_sync_log+0xbc8/0xd60 [btrfs]
RSP: 0018:ffff909a44d17bd0 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000001
RDX: ffff8f3be41cb940 RSI: ffffffffb0108d2b RDI: ffffffffb0108ff7
RBP: ffff909a44d17e70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000037988 R12: ffff8f3bd20e4000
R13: ffff8f3bd20e4428 R14: 00000000ffffff8b R15: ffff909a44d17c70
FS: 00007f6a6ed3fb80(0000) GS:ffff8f3c3dc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6a6ed3e000 CR3: 00000000525c0003 CR4: 0000000000160ee0
Call Trace:
? finish_wait+0x90/0x90
? __mutex_unlock_slowpath+0x45/0x2a0
? lock_acquire+0xa3/0x440
? lockref_put_or_lock+0x9/0x30
? dput+0x20/0x4a0
? dput+0x20/0x4a0
? do_raw_spin_unlock+0x4b/0xc0
? _raw_spin_unlock+0x1f/0x30
btrfs_sync_file+0x335/0x490 [btrfs]
do_fsync+0x38/0x70
__x64_sys_fsync+0x10/0x20
do_syscall_64+0x50/0xe0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f6a6ef1b6e3
Code: Bad RIP value.
RSP: 002b:00007ffd01e20038 EFLAGS: 00000246 ORIG_RAX: 000000000000004a
RAX: ffffffffffffffda RBX: 000000000007a120 RCX: 00007f6a6ef1b6e3
RDX: 00007ffd01e1ffa0 RSI: 00007ffd01e1ffa0 RDI: 0000000000000003
RBP: 0000000000000003 R08: 0000000000000001 R09: 00007ffd01e2004c
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000009f
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
irq event stamp: 0
hardirqs last enabled at (0): [<0000000000000000>] 0x0
hardirqs last disabled at (0): [<ffffffffb007fe0b>] copy_process+0x67b/0x1b00
softirqs last enabled at (0): [<ffffffffb007fe0b>] copy_process+0x67b/0x1b00
softirqs last disabled at (0): [<0000000000000000>] 0x0
---[ end trace af146e0e38433456 ]---
BTRFS: error (device dm-0) in btrfs_sync_log:3084: errno=-117 Filesystem corrupted
This ret came from btrfs_write_marked_extents(). If we get an aborted
transaction via EIO before, we'll see it in btree_write_cache_pages()
and return EUCLEAN, which gets printed as "Filesystem corrupted".
Except we shouldn't be returning EUCLEAN here, we need to be returning
EROFS because EUCLEAN is reserved for actual corruption, not IO errors.
We are inconsistent about our handling of BTRFS_FS_STATE_ERROR
elsewhere, but we want to use EROFS for this particular case. The
original transaction abort has the real error code for why we ended up
with an aborted transaction, all subsequent actions just need to return
EROFS because they may not have a trans handle and have no idea about
the original cause of the abort.
After patch "btrfs: don't WARN if we abort a transaction with EROFS" the
stacktrace will not be dumped either.
Reported-by: Eric Sandeen <esandeen@redhat.com>
CC: stable@vger.kernel.org # 5.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add full test stacktrace ]
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Add proper variable for the scrub page and use it instead of repeatedly
dereferencing the other structures.
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Use a simpler iteration over tree block pages, same what csum_tree_block
does: first page always exists, loop over the rest.
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Add proper variable for the scrub page and use it instead of repeatedly
dereferencing the other structures.
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
We have sectorsize same as PAGE_SIZE, the checksum can be calculated in
one go.
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Add proper variable for the scrub page and use it instead of repeatedly
dereferencing the other structures.
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
The page contents with the checksum is available during the entire
function so we don't need to make a copy.
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
BTRFS_SUPER_INFO_SIZE is 4096, and fits to a page on all supported
architectures, so we can calculate the checksum in one go.
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
As the page mapping has been removed, rename the variables to 'kaddr'
that we use everywhere else. The type is changed to 'char *' so pointer
arithmetic works without casts.
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
All pages that scrub uses in the scrub_block::pagev array are allocated
with GFP_KERNEL and never part of any mapping, so kmap is not necessary,
we only need to know the page address.
In scrub_write_page_to_dev_replace we don't even need to call
flush_dcache_page because of the same reason as above.
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
The main function to lookup a root by its id btrfs_get_fs_root takes the
whole key, while only using the objectid. The value of offset is preset
to (u64)-1 but not actually used until btrfs_find_root that does the
actual search.
Switch btrfs_get_fs_root to use only objectid and remove all local
variables that existed just for the lookup. The actual key for search is
set up in btrfs_get_fs_root, reusing another key variable.
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When scrubbing a stripe, whenever we find an extent we lookup for its
checksums in the checksum tree. However we do it even for metadata extents
which don't have checksum items stored in the checksum tree, that is
only for data extents.
So make the lookup for checksums only if we are processing with a data
extent.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Back in 2014, commit 04216820fe83d5 ("Btrfs: fix race between fs trimming
and block group remove/allocation"), I added the 'trimming' member to the
block group structure. Its purpose was to prevent races between trimming
and block group deletion/allocation by pinning the block group in a way
that prevents its logical address and device extents from being reused
while trimming is in progress for a block group, so that if another task
deletes the block group and then another task allocates a new block group
that gets the same logical address and device extents while the trimming
task is still in progress.
After the previous fix for scrub (patch "btrfs: fix a race between scrub
and block group removal/allocation"), scrub now also has the same needs that
trimming has, so the member name 'trimming' no longer makes sense.
Since there is already a 'pinned' member in the block group that refers
to space reservations (pinned bytes), rename the member to 'frozen',
add a comment on top of it to describe its general purpose and rename
the helpers to increment and decrement the counter as well, to match
the new member name.
The next patch in the series will move the helpers into a more suitable
file (from free-space-cache.c to block-group.c).
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When scrub is verifying the extents of a block group for a device, it is
possible that the corresponding block group gets removed and its logical
address and device extents get used for a new block group allocation.
When this happens scrub incorrectly reports that errors were detected
and, if the the new block group has a different profile then the old one,
deleted block group, we can crash due to a null pointer dereference.
Possibly other unexpected and weird consequences can happen as well.
Consider the following sequence of actions that leads to the null pointer
dereference crash when scrub is running in parallel with balance:
1) Balance sets block group X to read-only mode and starts relocating it.
Block group X is a metadata block group, has a raid1 profile (two
device extents, each one in a different device) and a logical address
of 19424870400;
2) Scrub is running and finds device extent E, which belongs to block
group X. It enters scrub_stripe() to find all extents allocated to
block group X, the search is done using the extent tree;
3) Balance finishes relocating block group X and removes block group X;
4) Balance starts relocating another block group and when trying to
commit the current transaction as part of the preparation step
(prepare_to_relocate()), it blocks because scrub is running;
5) The scrub task finds the metadata extent at the logical address
19425001472 and marks the pages of the extent to be read by a bio
(struct scrub_bio). The extent item's flags, which have the bit
BTRFS_EXTENT_FLAG_TREE_BLOCK set, are added to each page (struct
scrub_page). It is these flags in the scrub pages that tells the
bio's end io function (scrub_bio_end_io_worker) which type of extent
it is dealing with. At this point we end up with 4 pages in a bio
which is ready for submission (the metadata extent has a size of
16Kb, so that gives 4 pages on x86);
6) At the next iteration of scrub_stripe(), scrub checks that there is a
pause request from the relocation task trying to commit a transaction,
therefore it submits the pending bio and pauses, waiting for the
transaction commit to complete before resuming;
7) The relocation task commits the transaction. The device extent E, that
was used by our block group X, is now available for allocation, since
the commit root for the device tree was swapped by the transaction
commit;
8) Another task doing a direct IO write allocates a new data block group Y
which ends using device extent E. This new block group Y also ends up
getting the same logical address that block group X had: 19424870400.
This happens because block group X was the block group with the highest
logical address and, when allocating Y, find_next_chunk() returns the
end offset of the current last block group to be used as the logical
address for the new block group, which is
18351128576 + 1073741824 = 19424870400
So our new block group Y has the same logical address and device extent
that block group X had. However Y is a data block group, while X was
a metadata one, and Y has a raid0 profile, while X had a raid1 profile;
9) After allocating block group Y, the direct IO submits a bio to write
to device extent E;
10) The read bio submitted by scrub reads the 4 pages (16Kb) from device
extent E, which now correspond to the data written by the task that
did a direct IO write. Then at the end io function associated with
the bio, scrub_bio_end_io_worker(), we call scrub_block_complete()
which calls scrub_checksum(). This later function checks the flags
of the first page, and sees that the bit BTRFS_EXTENT_FLAG_TREE_BLOCK
is set in the flags, so it assumes it has a metadata extent and
then calls scrub_checksum_tree_block(). That functions returns an
error, since interpreting data as a metadata extent causes the
checksum verification to fail.
So this makes scrub_checksum() call scrub_handle_errored_block(),
which determines 'failed_mirror_index' to be 1, since the device
extent E was allocated as the second mirror of block group X.
It allocates BTRFS_MAX_MIRRORS scrub_block structures as an array at
'sblocks_for_recheck', and all the memory is initialized to zeroes by
kcalloc().
After that it calls scrub_setup_recheck_block(), which is responsible
for filling each of those structures. However, when that function
calls btrfs_map_sblock() against the logical address of the metadata
extent, 19425001472, it gets a struct btrfs_bio ('bbio') that matches
the current block group Y. However block group Y has a raid0 profile
and not a raid1 profile like X had, so the following call returns 1:
scrub_nr_raid_mirrors(bbio)
And as a result scrub_setup_recheck_block() only initializes the
first (index 0) scrub_block structure in 'sblocks_for_recheck'.
Then scrub_recheck_block() is called by scrub_handle_errored_block()
with the second (index 1) scrub_block structure as the argument,
because 'failed_mirror_index' was previously set to 1.
This scrub_block was not initialized by scrub_setup_recheck_block(),
so it has zero pages, its 'page_count' member is 0 and its 'pagev'
page array has all members pointing to NULL.
Finally when scrub_recheck_block() calls scrub_recheck_block_checksum()
we have a NULL pointer dereference when accessing the flags of the first
page, as pavev[0] is NULL:
static void scrub_recheck_block_checksum(struct scrub_block *sblock)
{
(...)
if (sblock->pagev[0]->flags & BTRFS_EXTENT_FLAG_DATA)
scrub_checksum_data(sblock);
(...)
}
Producing a stack trace like the following:
[542998.008985] BUG: kernel NULL pointer dereference, address: 0000000000000028
[542998.010238] #PF: supervisor read access in kernel mode
[542998.010878] #PF: error_code(0x0000) - not-present page
[542998.011516] PGD 0 P4D 0
[542998.011929] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
[542998.012786] CPU: 3 PID: 4846 Comm: kworker/u8:1 Tainted: G B W 5.6.0-rc7-btrfs-next-58 #1
[542998.014524] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
[542998.016065] Workqueue: btrfs-scrub btrfs_work_helper [btrfs]
[542998.017255] RIP: 0010:scrub_recheck_block_checksum+0xf/0x20 [btrfs]
[542998.018474] Code: 4c 89 e6 ...
[542998.021419] RSP: 0018:ffffa7af0375fbd8 EFLAGS: 00010202
[542998.022120] RAX: 0000000000000000 RBX: ffff9792e674d120 RCX: 0000000000000000
[542998.023178] RDX: 0000000000000001 RSI: ffff9792e674d120 RDI: ffff9792e674d120
[542998.024465] RBP: 0000000000000000 R08: 0000000000000067 R09: 0000000000000001
[542998.025462] R10: ffffa7af0375fa50 R11: 0000000000000000 R12: ffff9791f61fe800
[542998.026357] R13: ffff9792e674d120 R14: 0000000000000001 R15: ffffffffc0e3dfc0
[542998.027237] FS: 0000000000000000(0000) GS:ffff9792fb200000(0000) knlGS:0000000000000000
[542998.028327] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[542998.029261] CR2: 0000000000000028 CR3: 00000000b3b18003 CR4: 00000000003606e0
[542998.030301] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[542998.031316] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[542998.032380] Call Trace:
[542998.032752] scrub_recheck_block+0x162/0x400 [btrfs]
[542998.033500] ? __alloc_pages_nodemask+0x31e/0x460
[542998.034228] scrub_handle_errored_block+0x6f8/0x1920 [btrfs]
[542998.035170] scrub_bio_end_io_worker+0x100/0x520 [btrfs]
[542998.035991] btrfs_work_helper+0xaa/0x720 [btrfs]
[542998.036735] process_one_work+0x26d/0x6a0
[542998.037275] worker_thread+0x4f/0x3e0
[542998.037740] ? process_one_work+0x6a0/0x6a0
[542998.038378] kthread+0x103/0x140
[542998.038789] ? kthread_create_worker_on_cpu+0x70/0x70
[542998.039419] ret_from_fork+0x3a/0x50
[542998.039875] Modules linked in: dm_snapshot dm_thin_pool ...
[542998.047288] CR2: 0000000000000028
[542998.047724] ---[ end trace bde186e176c7f96a ]---
This issue has been around for a long time, possibly since scrub exists.
The last time I ran into it was over 2 years ago. After recently fixing
fstests to pass the "--full-balance" command line option to btrfs-progs
when doing balance, several tests started to more heavily exercise balance
with fsstress, scrub and other operations in parallel, and therefore
started to hit this issue again (with btrfs/061 for example).
Fix this by having scrub increment the 'trimming' counter of the block
group, which pins the block group in such a way that it guarantees neither
its logical address nor device extents can be reused by future block group
allocations until we decrement the 'trimming' counter. Also make sure that
on each iteration of scrub_stripe() we stop scrubbing the block group if
it was removed already.
A later patch in the series will rename the block group's 'trimming'
counter and its helpers to a more generic name, since now it is not used
exclusively for pinning while trimming anymore.
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array
member[1][2], introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning in
case the flexible array does not occur last in the structure, which will
help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by this
change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero." [1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
We are now using these for all roots, rename them to btrfs_put_root()
and btrfs_grab_root();
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Now that all callers of btrfs_get_fs_root are subsequently calling
btrfs_grab_fs_root and handling dropping the ref when they are done
appropriately, go ahead and push btrfs_grab_fs_root up into
btrfs_get_fs_root.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
We look up the root for the bytenr that is failing, so we need to hold a
ref on the root for that operation.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
All this does is call btrfs_get_fs_root() with check_ref == true. Just
use btrfs_get_fs_root() so we don't have a bunch of different helpers
that do the same thing.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull btrfs updates from David Sterba:
"Features, highlights:
- async discard
- "mount -o discard=async" to enable it
- freed extents are not discarded immediatelly, but grouped
together and trimmed later, with IO rate limiting
- the "sync" mode submits short extents that could have been
ignored completely by the device, for SATA prior to 3.1 the
requests are unqueued and have a big impact on performance
- the actual discard IO requests have been moved out of
transaction commit to a worker thread, improving commit latency
- IO rate and request size can be tuned by sysfs files, for now
enabled only with CONFIG_BTRFS_DEBUG as we might need to
add/delete the files and don't have a stable-ish ABI for
general use, defaults are conservative
- export device state info in sysfs, eg. missing, writeable
- no discard of extents known to be untouched on disk (eg. after
reservation)
- device stats reset is logged with process name and PID that called
the ioctl
Fixes:
- fix missing hole after hole punching and fsync when using NO_HOLES
- writeback: range cyclic mode could miss some dirty pages and lead
to OOM
- two more corner cases for metadata_uuid change after power loss
during the change
- fix infinite loop during fsync after mix of rename operations
Core changes:
- qgroup assign returns ENOTCONN when quotas not enabled, used to
return EINVAL that was confusing
- device closing does not need to allocate memory anymore
- snapshot aware code got removed, disabled for years due to
performance problems, reimplmentation will allow to select wheter
defrag breaks or does not break COW on shared extents
- tree-checker:
- check leaf chunk item size, cross check against number of
stripes
- verify location keys for DIR_ITEM, DIR_INDEX and XATTR items
- new self test for physical -> logical mapping code, used for super
block range exclusion
- assertion helpers/macros updated to avoid objtool "unreachable
code" reports on older compilers or config option combinations"
* tag 'for-5.6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (84 commits)
btrfs: free block groups after free'ing fs trees
btrfs: Fix split-brain handling when changing FSID to metadata uuid
btrfs: Handle another split brain scenario with metadata uuid feature
btrfs: Factor out metadata_uuid code from find_fsid.
btrfs: Call find_fsid from find_fsid_inprogress
Btrfs: fix infinite loop during fsync after rename operations
btrfs: set trans->drity in btrfs_commit_transaction
btrfs: drop log root for dropped roots
btrfs: sysfs, add devid/dev_state kobject and device attributes
btrfs: Refactor btrfs_rmap_block to improve readability
btrfs: Add self-tests for btrfs_rmap_block
btrfs: selftests: Add support for dummy devices
btrfs: Move and unexport btrfs_rmap_block
btrfs: separate definition of assertion failure handlers
btrfs: device stats, log when stats are zeroed
btrfs: fix improper setting of scanned for range cyclic write cache pages
btrfs: safely advance counter when looking up bio csums
btrfs: remove unused member btrfs_device::work
btrfs: remove unnecessary wrapper get_alloc_profile
btrfs: add correction to handle -1 edge case in async discard
...
|
|
[BUG]
For dev-replace test cases with fsstress, like btrfs/06[45] btrfs/071,
looped runs can lead to random failure, where scrub finds csum error.
The possibility is not high, around 1/20 to 1/100, but it's causing data
corruption.
The bug is observable after commit b12de52896c0 ("btrfs: scrub: Don't
check free space before marking a block group RO")
[CAUSE]
Dev-replace has two source of writes:
- Write duplication
All writes to source device will also be duplicated to target device.
Content: Not yet persisted data/meta
- Scrub copy
Dev-replace reused scrub code to iterate through existing extents, and
copy the verified data to target device.
Content: Previously persisted data and metadata
The difference in contents makes the following race possible:
Regular Writer | Dev-replace
-----------------------------------------------------------------
^ |
| Preallocate one data extent |
| at bytenr X, len 1M |
v |
^ Commit transaction |
| Now extent [X, X+1M) is in |
v commit root |
================== Dev replace starts =========================
| ^
| | Scrub extent [X, X+1M)
| | Read [X, X+1M)
| | (The content are mostly garbage
| | since it's preallocated)
^ | v
| Write back happens for |
| extent [X, X+512K) |
| New data writes to both |
| source and target dev. |
v |
| ^
| | Scrub writes back extent [X, X+1M)
| | to target device.
| | This will over write the new data in
| | [X, X+512K)
| v
This race can only happen for nocow writes. Thus metadata and data cow
writes are safe, as COW will never overwrite extents of previous
transaction (in commit root).
This behavior can be confirmed by disabling all fallocate related calls
in fsstress (*), then all related tests can pass a 2000 run loop.
*: FSSTRESS_AVOID="-f fallocate=0 -f allocsp=0 -f zero=0 -f insert=0 \
-f collapse=0 -f punch=0 -f resvsp=0"
I didn't expect resvsp ioctl will fallback to fallocate in VFS...
[FIX]
Make dev-replace to require mandatory block group RO, and wait for current
nocow writes before calling scrub_chunk().
This patch will mostly revert commit 76a8efa171bf ("btrfs: Continue replace
when set_block_ro failed") for dev-replace path.
The side effect is, dev-replace can be more strict on avaialble space, but
definitely worth to avoid data corruption.
Reported-by: Filipe Manana <fdmanana@suse.com>
Fixes: 76a8efa171bf ("btrfs: Continue replace when set_block_ro failed")
Fixes: b12de52896c0 ("btrfs: scrub: Don't check free space before marking a block group RO")
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
block_group removal is a little tricky. It can race with the extent
allocator, the cleaner thread, and balancing. The current path is for a
block_group to be added to the unused_bgs list. Then, when the cleaner
thread comes around, it starts a transaction and then proceeds with
removing the block_group. Extents that are pinned are subsequently
removed from the pinned trees and then eventually a discard is issued
for the entire block_group.
Async discard introduces another player into the game, the discard
workqueue. While it has none of the racing issues, the new problem is
ensuring we don't leave free space untrimmed prior to forgetting the
block_group. This is handled by placing fully free block_groups on a
separate discard queue. This is necessary to maintain discarding order
as in the future we will slowly trim even fully free block_groups. The
ordering helps us make progress on the same block_group rather than say
the last fully freed block_group or needing to search through the fully
freed block groups at the beginning of a list and insert after.
The new order of events is a fully freed block group gets placed on the
unused discard queue first. Once it's processed, it will be placed on
the unusued_bgs list and then the original sequence of events will
happen, just without the final whole block_group discard.
The mount flags can change when processing unused_bgs, so when flipping
from DISCARD to DISCARD_ASYNC, the unused_bgs must be punted to the
discard_list to be trimmed. If we flip off DISCARD_ASYNC, we punt
free block groups on the discard_list to the unused_bg queue which will
do the final discard for us.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When doing a device replace, while at scrub.c:scrub_enumerate_chunks(), we
set the block group to RO mode and then wait for any ongoing writes into
extents of the block group to complete. While doing that wait we overwrite
the value of the variable 'ret' and can break out of the loop if an error
happens without turning the block group back into RW mode. So what happens
is the following:
1) btrfs_inc_block_group_ro() returns 0, meaning it set the block group
to RO mode (its ->ro field set to 1 or incremented to some value > 1);
2) Then btrfs_wait_ordered_roots() returns a value > 0;
3) Then if either joining or committing the transaction fails, we break
out of the loop wihtout calling btrfs_dec_block_group_ro(), leaving
the block group in RO mode forever.
To fix this, just remove the code that waits for ongoing writes to extents
of the block group, since it's not needed because in the initial setup
phase of a device replace operation, before starting to find all chunks
and their extents, we set the target device for replace while holding
fs_info->dev_replace->rwsem, which ensures that after releasing that
semaphore, any writes into the source device are made to the target device
as well (__btrfs_map_block() guarantees that). So while at
scrub_enumerate_chunks() we only need to worry about finding and copying
extents (from the source device to the target device) that were written
before we started the device replace operation.
Fixes: f0e9b7d6401959 ("Btrfs: fix race setting block group readonly during device replace")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
[BUG]
When running btrfs/072 with only one online CPU, it has a pretty high
chance to fail:
btrfs/072 12s ... _check_dmesg: something found in dmesg (see xfstests-dev/results//btrfs/072.dmesg)
- output mismatch (see xfstests-dev/results//btrfs/072.out.bad)
--- tests/btrfs/072.out 2019-10-22 15:18:14.008965340 +0800
+++ /xfstests-dev/results//btrfs/072.out.bad 2019-11-14 15:56:45.877152240 +0800
@@ -1,2 +1,3 @@
QA output created by 072
Silence is golden
+Scrub find errors in "-m dup -d single" test
...
And with the following call trace:
BTRFS info (device dm-5): scrub: started on devid 1
------------[ cut here ]------------
BTRFS: Transaction aborted (error -27)
WARNING: CPU: 0 PID: 55087 at fs/btrfs/block-group.c:1890 btrfs_create_pending_block_groups+0x3e6/0x470 [btrfs]
CPU: 0 PID: 55087 Comm: btrfs Tainted: G W O 5.4.0-rc1-custom+ #13
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:btrfs_create_pending_block_groups+0x3e6/0x470 [btrfs]
Call Trace:
__btrfs_end_transaction+0xdb/0x310 [btrfs]
btrfs_end_transaction+0x10/0x20 [btrfs]
btrfs_inc_block_group_ro+0x1c9/0x210 [btrfs]
scrub_enumerate_chunks+0x264/0x940 [btrfs]
btrfs_scrub_dev+0x45c/0x8f0 [btrfs]
btrfs_ioctl+0x31a1/0x3fb0 [btrfs]
do_vfs_ioctl+0x636/0xaa0
ksys_ioctl+0x67/0x90
__x64_sys_ioctl+0x43/0x50
do_syscall_64+0x79/0xe0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
---[ end trace 166c865cec7688e7 ]---
[CAUSE]
The error number -27 is -EFBIG, returned from the following call chain:
btrfs_end_transaction()
|- __btrfs_end_transaction()
|- btrfs_create_pending_block_groups()
|- btrfs_finish_chunk_alloc()
|- btrfs_add_system_chunk()
This happens because we have used up all space of
btrfs_super_block::sys_chunk_array.
The root cause is, we have the following bad loop of creating tons of
system chunks:
1. The only SYSTEM chunk is being scrubbed
It's very common to have only one SYSTEM chunk.
2. New SYSTEM bg will be allocated
As btrfs_inc_block_group_ro() will check if we have enough space
after marking current bg RO. If not, then allocate a new chunk.
3. New SYSTEM bg is still empty, will be reclaimed
During the reclaim, we will mark it RO again.
4. That newly allocated empty SYSTEM bg get scrubbed
We go back to step 2, as the bg is already mark RO but still not
cleaned up yet.
If the cleaner kthread doesn't get executed fast enough (e.g. only one
CPU), then we will get more and more empty SYSTEM chunks, using up all
the space of btrfs_super_block::sys_chunk_array.
[FIX]
Since scrub/dev-replace doesn't always need to allocate new extent,
especially chunk tree extent, so we don't really need to do chunk
pre-allocation.
To break above spiral, here we introduce a new parameter to
btrfs_inc_block_group(), @do_chunk_alloc, which indicates whether we
need extra chunk pre-allocation.
For relocation, we pass @do_chunk_alloc=true, while for scrub, we pass
@do_chunk_alloc=false.
This should keep unnecessary empty chunks from popping up for scrub.
Also, since there are two parameters for btrfs_inc_block_group_ro(),
add more comment for it.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
The type name is misleading, a single entry is named 'cache' while this
normally means a collection of objects. Rename that everywhere. Also the
identifier was quite long, making function prototypes harder to format.
Suggested-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
The "&fs_info->dev_replace.rwsem" and "&dev_replace->rwsem" refer to
the same lock but Smatch is not clever enough to figure that out so it
leads to static checker warnings. It's better to use it consistently
anyway.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
The on-disk format of block group item makes use of the key that stores
the offset and length. This is further used in the code, although this
makes thing harder to understand. The key is also packed so the
offset/length is not properly aligned as u64.
Add start (key.objectid) and length (key.offset) members to block group
and remove the embedded key. When the item is searched or written, a
local variable for key is used.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
For unknown reasons, the member 'used' in the block group struct is
stored in the b-tree item and accessed everywhere using the special
accessor helper. Let's unify it and make it a regular member and only
update the item before writing it to the tree.
The item is still being used for flags and chunk_objectid, there's some
duplication until the item is removed in following patches.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
