- 31 Jan, 2020 2 commits
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Josef Bacik authored
There exists a deadlock with range_cyclic that has existed forever. If we loop around with a bio already built we could deadlock with a writer who has the page locked that we're attempting to write but is waiting on a page in our bio to be written out. The task traces are as follows PID: 1329874 TASK: ffff889ebcdf3800 CPU: 33 COMMAND: "kworker/u113:5" #0 [ffffc900297bb658] __schedule at ffffffff81a4c33f #1 [ffffc900297bb6e0] schedule at ffffffff81a4c6e3 #2 [ffffc900297bb6f8] io_schedule at ffffffff81a4ca42 #3 [ffffc900297bb708] __lock_page at ffffffff811f145b #4 [ffffc900297bb798] __process_pages_contig at ffffffff814bc502 #5 [ffffc900297bb8c8] lock_delalloc_pages at ffffffff814bc684 #6 [ffffc900297bb900] find_lock_delalloc_range at ffffffff814be9ff #7 [ffffc900297bb9a0] writepage_delalloc at ffffffff814bebd0 #8 [ffffc900297bba18] __extent_writepage at ffffffff814bfbf2 #9 [ffffc900297bba98] extent_write_cache_pages at ffffffff814bffbd PID: 2167901 TASK: ffff889dc6a59c00 CPU: 14 COMMAND: "aio-dio-invalid" #0 [ffffc9003b50bb18] __schedule at ffffffff81a4c33f #1 [ffffc9003b50bba0] schedule at ffffffff81a4c6e3 #2 [ffffc9003b50bbb8] io_schedule at ffffffff81a4ca42 #3 [ffffc9003b50bbc8] wait_on_page_bit at ffffffff811f24d6 #4 [ffffc9003b50bc60] prepare_pages at ffffffff814b05a7 #5 [ffffc9003b50bcd8] btrfs_buffered_write at ffffffff814b1359 #6 [ffffc9003b50bdb0] btrfs_file_write_iter at ffffffff814b5933 #7 [ffffc9003b50be38] new_sync_write at ffffffff8128f6a8 #8 [ffffc9003b50bec8] vfs_write at ffffffff81292b9d #9 [ffffc9003b50bf00] ksys_pwrite64 at ffffffff81293032 I used drgn to find the respective pages we were stuck on page_entry.page 0xffffea00fbfc7500 index 8148 bit 15 pid 2167901 page_entry.page 0xffffea00f9bb7400 index 7680 bit 0 pid 1329874 As you can see the kworker is waiting for bit 0 (PG_locked) on index 7680, and aio-dio-invalid is waiting for bit 15 (PG_writeback) on index 8148. aio-dio-invalid has 7680, and the kworker epd looks like the following crash> struct extent_page_data ffffc900297bbbb0 struct extent_page_data { bio = 0xffff889f747ed830, tree = 0xffff889eed6ba448, extent_locked = 0, sync_io = 0 } Probably worth mentioning as well that it waits for writeback of the page to complete while holding a lock on it (at prepare_pages()). Using drgn I walked the bio pages looking for page 0xffffea00fbfc7500 which is the one we're waiting for writeback on bio = Object(prog, 'struct bio', address=0xffff889f747ed830) for i in range(0, bio.bi_vcnt.value_()): bv = bio.bi_io_vec[i] if bv.bv_page.value_() == 0xffffea00fbfc7500: print("FOUND IT") which validated what I suspected. The fix for this is simple, flush the epd before we loop back around to the beginning of the file during writeout. Fixes: b293f02e ("Btrfs: Add writepages support") CC: stable@vger.kernel.org # 4.4+ Reviewed-by:Filipe Manana <fdmanana@suse.com> Signed-off-by:
Josef Bacik <josef@toxicpanda.com> Signed-off-by:
David Sterba <dsterba@suse.com>
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Filipe Manana authored
There is a race between adding and removing elements to the tree mod log list and rbtree that can lead to use-after-free problems. Consider the following example that explains how/why the problems happens: 1) Task A has mod log element with sequence number 200. It currently is the only element in the mod log list; 2) Task A calls btrfs_put_tree_mod_seq() because it no longer needs to access the tree mod log. When it enters the function, it initializes 'min_seq' to (u64)-1. Then it acquires the lock 'tree_mod_seq_lock' before checking if there are other elements in the mod seq list. Since the list it empty, 'min_seq' remains set to (u64)-1. Then it unlocks the lock 'tree_mod_seq_lock'; 3) Before task A acquires the lock 'tree_mod_log_lock', task B adds itself to the mod seq list through btrfs_get_tree_mod_seq() and gets a sequence number of 201; 4) Some other task, name it task C, modifies a btree and because there elements in the mod seq list, it adds a tree mod elem to the tree mod log rbtree. That node added to the mod log rbtree is assigned a sequence number of 202; 5) Task B, which is doing fiemap and resolving indirect back references, calls btrfs get_old_root(), with 'time_seq' == 201, which in turn calls tree_mod_log_search() - the search returns the mod log node from the rbtree with sequence number 202, created by task C; 6) Task A now acquires the lock 'tree_mod_log_lock', starts iterating the mod log rbtree and finds the node with sequence number 202. Since 202 is less than the previously computed 'min_seq', (u64)-1, it removes the node and frees it; 7) Task B still has a pointer to the node with sequence number 202, and it dereferences the pointer itself and through the call to __tree_mod_log_rewind(), resulting in a use-after-free problem. This issue can be triggered sporadically with the test case generic/561 from fstests, and it happens more frequently with a higher number of duperemove processes. When it happens to me, it either freezes the VM or it produces a trace like the following before crashing: [ 1245.321140] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI [ 1245.321200] CPU: 1 PID: 26997 Comm: pool Not tainted 5.5.0-rc6-btrfs-next-52 #1 [ 1245.321235] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014 [ 1245.321287] RIP: 0010:rb_next+0x16/0x50 [ 1245.321307] Code: .... [ 1245.321372] RSP: 0018:ffffa151c4d039b0 EFLAGS: 00010202 [ 1245.321388] RAX: 6b6b6b6b6b6b6b6b RBX: ffff8ae221363c80 RCX: 6b6b6b6b6b6b6b6b [ 1245.321409] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff8ae221363c80 [ 1245.321439] RBP: ffff8ae20fcc4688 R08: 0000000000000002 R09: 0000000000000000 [ 1245.321475] R10: ffff8ae20b120910 R11: 00000000243f8bb1 R12: 0000000000000038 [ 1245.321506] R13: ffff8ae221363c80 R14: 000000000000075f R15: ffff8ae223f762b8 [ 1245.321539] FS: 00007fdee1ec7700(0000) GS:ffff8ae236c80000(0000) knlGS:0000000000000000 [ 1245.321591] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1245.321614] CR2: 00007fded4030c48 CR3: 000000021da16003 CR4: 00000000003606e0 [ 1245.321642] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1245.321668] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 1245.321706] Call Trace: [ 1245.321798] __tree_mod_log_rewind+0xbf/0x280 [btrfs] [ 1245.321841] btrfs_search_old_slot+0x105/0xd00 [btrfs] [ 1245.321877] resolve_indirect_refs+0x1eb/0xc60 [btrfs] [ 1245.321912] find_parent_nodes+0x3dc/0x11b0 [btrfs] [ 1245.321947] btrfs_check_shared+0x115/0x1c0 [btrfs] [ 1245.321980] ? extent_fiemap+0x59d/0x6d0 [btrfs] [ 1245.322029] extent_fiemap+0x59d/0x6d0 [btrfs] [ 1245.322066] do_vfs_ioctl+0x45a/0x750 [ 1245.322081] ksys_ioctl+0x70/0x80 [ 1245.322092] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 1245.322113] __x64_sys_ioctl+0x16/0x20 [ 1245.322126] do_syscall_64+0x5c/0x280 [ 1245.322139] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 1245.322155] RIP: 0033:0x7fdee3942dd7 [ 1245.322177] Code: .... [ 1245.322258] RSP: 002b:00007fdee1ec6c88 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 1245.322294] RAX: ffffffffffffffda RBX: 00007fded40210d8 RCX: 00007fdee3942dd7 [ 1245.322314] RDX: 00007fded40210d8 RSI: 00000000c020660b RDI: 0000000000000004 [ 1245.322337] RBP: 0000562aa89e7510 R08: 0000000000000000 R09: 00007fdee1ec6d44 [ 1245.322369] R10: 0000000000000073 R11: 0000000000000246 R12: 00007fdee1ec6d48 [ 1245.322390] R13: 00007fdee1ec6d40 R14: 00007fded40210d0 R15: 00007fdee1ec6d50 [ 1245.322423] Modules linked in: .... [ 1245.323443] ---[ end trace 01de1e9ec5dff3cd ]--- Fix this by ensuring that btrfs_put_tree_mod_seq() computes the minimum sequence number and iterates the rbtree while holding the lock 'tree_mod_log_lock' in write mode. Also get rid of the 'tree_mod_seq_lock' lock, since it is now redundant. Fixes: bd989ba3 ("Btrfs: add tree modification log functions") Fixes: 097b8a7c ("Btrfs: join tree mod log code with the code holding back delayed refs") CC: stable@vger.kernel.org # 4.4+ Reviewed-by:
Nikolay Borisov <nborisov@suse.com> Signed-off-by:
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- 23 Jan, 2020 14 commits
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Josef Bacik authored
Sometimes when running generic/475 we would trip the WARN_ON(cache->reserved) check when free'ing the block groups on umount. This is because sometimes we don't commit the transaction because of IO errors and thus do not cleanup the tree logs until at umount time. These blocks are still reserved until they are cleaned up, but they aren't cleaned up until _after_ we do the free block groups work. Fix this by moving the free after free'ing the fs roots, that way all of the tree logs are cleaned up and we have a properly cleaned fs. A bunch of loops of generic/475 confirmed this fixes the problem. CC: stable@vger.kernel.org # 4.9+ Signed-off-by:
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Nikolay Borisov authored
Current code doesn't correctly handle the situation which arises when a file system that has METADATA_UUID_INCOMPAT flag set and has its FSID changed to the one in metadata uuid. This causes the incompat flag to disappear. In case of a power failure we could end up in a situation where part of the disks in a multi-disk filesystem are correctly reverted to METADATA_UUID_INCOMPAT flag unset state, while others have METADATA_UUID_INCOMPAT set and CHANGING_FSID_V2_IN_PROGRESS. This patch corrects the behavior required to handle the case where a disk of the second type is scanned first, creating the necessary btrfs_fs_devices. Subsequently, when a disk which has already completed the transition is scanned it should overwrite the data in btrfs_fs_devices. Reported-by:
Su Yue <Damenly_Su@gmx.com> Reviewed-by:
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Nikolay Borisov authored
There is one more cases which isn't handled by the original metadata uuid work. Namely, when a filesystem has METADATA_UUID incompat bit and the user decides to change the FSID to the original one e.g. have metadata_uuid and fsid match. In case of power failure while this operation is in progress we could end up in a situation where some of the disks have the incompat bit removed and the other half have both METADATA_UUID_INCOMPAT and FSID_CHANGING_IN_PROGRESS flags. This patch handles the case where a disk that has successfully changed its FSID such that it equals METADATA_UUID is scanned first. Subsequently when a disk with both METADATA_UUID_INCOMPAT/FSID_CHANGING_IN_PROGRESS flags is scanned find_fsid_changed won't be able to find an appropriate btrfs_fs_devices. This is done by extending find_fsid_changed to correctly find btrfs_fs_devices whose metadata_uuid/fsid are the same and they match the metadata_uuid of the currently scanned device. Fixes: cc5de4e7 ("btrfs: Handle final split-brain possibility during fsid change") Reviewed-by:
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Su Yue authored
find_fsid became rather hairy with the introduction of metadata uuid changing feature. Alleviate this by factoring out the metadata uuid specific code in a dedicated function which deals with finding correct fsid for a device with changed uuid. Reviewed-by:
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Su Yue authored
Since find_fsid_inprogress should also handle the case in which an fs didn't change its FSID make it call find_fsid directly. This makes the code in device_list_add simpler by eliminating a conditional call of find_fsid. No functional changes. Reviewed-by:
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Filipe Manana authored
Recently fsstress (from fstests) sporadically started to trigger an infinite loop during fsync operations. This turned out to be because support for the rename exchange and whiteout operations was added to fsstress in fstests. These operations, unlike any others in fsstress, cause file names to be reused, whence triggering this issue. However it's not necessary to use rename exchange and rename whiteout operations trigger this issue, simple rename operations and file creations are enough to trigger the issue. The issue boils down to when we are logging inodes that conflict (that had the name of any inode we need to log during the fsync operation), we keep logging them even if they were already logged before, and after that we check if there's any other inode that conflicts with them and then add it again to the list of inodes to log. Skipping already logged inodes fixes the issue. Consider the following example: $ mkfs.btrfs -f /dev/sdb $ mount /dev/sdb /mnt $ mkdir /mnt/testdir # inode 257 $ touch /mnt/testdir/zz # inode 258 $ ln /mnt/testdir/zz /mnt/testdir/zz_link $ touch /mnt/testdir/a # inode 259 $ sync # The following 3 renames achieve the same result as a rename exchange # operation (<rename_exchange> /mnt/testdir/zz_link to /mnt/testdir/a). $ mv /mnt/testdir/a /mnt/testdir/a/tmp $ mv /mnt/testdir/zz_link /mnt/testdir/a $ mv /mnt/testdir/a/tmp /mnt/testdir/zz_link # The following rename and file creation give the same result as a # rename whiteout operation (<rename_whiteout> zz to a2). $ mv /mnt/testdir/zz /mnt/testdir/a2 $ touch /mnt/testdir/zz # inode 260 $ xfs_io -c fsync /mnt/testdir/zz --> results in the infinite loop The following steps happen: 1) When logging inode 260, we find that its reference named "zz" was used by inode 258 in the previous transaction (through the commit root), so inode 258 is added to the list of conflicting indoes that need to be logged; 2) After logging inode 258, we find that its reference named "a" was used by inode 259 in the previous transaction, and therefore we add inode 259 to the list of conflicting inodes to be logged; 3) After logging inode 259, we find that its reference named "zz_link" was used by inode 258 in the previous transaction - we add inode 258 to the list of conflicting inodes to log, again - we had already logged it before at step 3. After logging it again, we find again that inode 259 conflicts with him, and we add again 259 to the list, etc - we end up repeating all the previous steps. So fix this by skipping logging of conflicting inodes that were already logged. Fixes: 6b5fc433 ("Btrfs: fix fsync after succession of renames of different files") CC: stable@vger.kernel.org # 5.1+ Signed-off-by: -
Josef Bacik authored
If we abort a transaction we have the following sequence if (!trans->dirty && list_empty(&trans->new_bgs)) return; WRITE_ONCE(trans->transaction->aborted, err); The idea being if we didn't modify anything with our trans handle then we don't really need to abort the whole transaction, maybe the other trans handles are fine and we can carry on. However in the case of create_snapshot we add a pending_snapshot object to our transaction and then commit the transaction. We don't actually modify anything. sync() behaves the same way, attach to an existing transaction and commit it. This means that if we have an IO error in the right places we could abort the committing transaction with our trans->dirty being not set and thus not set transaction->aborted. This is a problem because in the create_snapshot() case we depend on pending->error being set to something, or btrfs_commit_transaction returning an error. If we are not the trans handle that gets to commit the transaction, and we're waiting on the commit to happen we get our return value from cur_trans->aborted. If this was not set to anything because sync() hit an error in the transaction commit before it could modify anything then cur_trans->aborted would be 0. Thus we'd return 0 from btrfs_commit_transaction() in create_snapshot. This is a problem because we then try to do things with pending_snapshot->snap, which will be NULL because we didn't create the snapshot, and then we'll get a NULL pointer dereference like the following "BUG: kernel NULL pointer dereference, address: 00000000000001f0" RIP: 0010:btrfs_orphan_cleanup+0x2d/0x330 Call Trace: ? btrfs_mksubvol.isra.31+0x3f2/0x510 btrfs_mksubvol.isra.31+0x4bc/0x510 ? __sb_start_write+0xfa/0x200 ? mnt_want_write_file+0x24/0x50 btrfs_ioctl_snap_create_transid+0x16c/0x1a0 btrfs_ioctl_snap_create_v2+0x11e/0x1a0 btrfs_ioctl+0x1534/0x2c10 ? free_debug_processing+0x262/0x2a3 do_vfs_ioctl+0xa6/0x6b0 ? do_sys_open+0x188/0x220 ? syscall_trace_enter+0x1f8/0x330 ksys_ioctl+0x60/0x90 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x4a/0x1b0 In order to fix this we need to make sure anybody who calls commit_transaction has trans->dirty set so that they properly set the trans->transaction->aborted value properly so any waiters know bad things happened. This was found while I was running generic/475 with my modified fsstress, it reproduced within a few runs. I ran with this patch all night and didn't see the problem again. CC: stable@vger.kernel.org # 4.4+ Signed-off-by:
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Josef Bacik authored
If we fsync on a subvolume and create a log root for that volume, and then later delete that subvolume we'll never clean up its log root. Fix this by making switch_commit_roots free the log for any dropped roots we encounter. The extra churn is because we need a btrfs_trans_handle, not the btrfs_transaction. CC: stable@vger.kernel.org # 5.4+ Reviewed-by:
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Anand Jain authored
New sysfs attributes that track the filesystem status of devices, stored in the per-filesystem directory in /sys/fs/btrfs/FSID/devinfo . There's a directory for each device, with name corresponding to the numerical device id. in_fs_metadata - device is in the list of fs metadata missing - device is missing (no device node or block device) replace_target - device is target of replace writeable - writes from fs are allowed These attributes reflect the state of the device::dev_state and created at mount time. Sample output: $ pwd /sys/fs/btrfs/6e1961f1-5918-4ecc-a22f-948897b409f7/devinfo/1/ $ ls in_fs_metadata missing replace_target writeable $ cat missing 0 The output from these attributes are 0 or 1. 0 indicates unset and 1 indicates set. These attributes are readonly. It is observed that the device delete thread and sysfs read thread will not race because the delete thread calls sysfs kobject_put() which in turn waits for existing sysfs read to complete. Note for device replace devid swap: During the replace the target device temporarily assumes devid 0 before assigning the devid of the soruce device. In btrfs_dev_replace_finishing() we remove source sysfs devid using the function btrfs_sysfs_remove_devices_attr(), so after that call kobject_rename() to update the devid in the sysfs. This adds and calls btrfs_sysfs_update_devid() helper function to update the device id. Signed-off-by:Anand Jain <anand.jain@oracle.com> Reviewed-by:
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Nikolay Borisov authored
Move variables to appropriate scope. Remove last BUG_ON in the function and rework error handling accordingly. Make the duplicate detection code more straightforward. Use in_range macro. And give variables more descriptive name by explicitly distinguishing between IO stripe size (size recorded in the chunk item) and data stripe size (the size of an actual stripe, constituting a logical chunk/block group). Signed-off-by:
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Nikolay Borisov authored
Add RAID1 and single testcases to verify that data stripes are excluded from super block locations and that the address mapping is valid. Signed-off-by:
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Nikolay Borisov authored
Add basic infrastructure to create and link dummy btrfs_devices. This will be used in the pending btrfs_rmap_block test which deals with the block groups. Calling btrfs_alloc_dummy_device will link the newly created device to the passed fs_info and the test framework will free them once the test is finished. Signed-off-by:
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Nikolay Borisov authored
It's used only during initial block group reading to map physical address of super block to a list of logical ones. Make it private to block-group.c, add proper kernel doc and ensure it's exported only for tests. Signed-off-by:
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David Sterba authored
There's a report where objtool detects unreachable instructions, eg.: fs/btrfs/ctree.o: warning: objtool: btrfs_search_slot()+0x2d4: unreachable instruction This seems to be a false positive due to compiler version. The cause is in the ASSERT macro implementation that does the conditional check as IS_DEFINED(CONFIG_BTRFS_ASSERT) and not an #ifdef. To avoid that, use the ifdefs directly. There are still 2 reports that aren't fixed: fs/btrfs/extent_io.o: warning: objtool: __set_extent_bit()+0x71f: unreachable instruction fs/btrfs/relocation.o: warning: objtool: find_data_references()+0x4e0: unreachable instruction Co-developed-by:
Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by:
Randy Dunlap <rdunlap@infradead.org> Signed-off-by:
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- 20 Jan, 2020 24 commits
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Anand Jain authored
We had a report indicating that some read errors aren't reported by the device stats in the userland. It is important to have the errors reported in the device stat as user land scripts might depend on it to take the reasonable corrective actions. But to debug these issue we need to be really sure that request to reset the device stat did not come from the userland itself. So log an info message when device error reset happens. For example: BTRFS info (device sdc): device stats zeroed by btrfs(9223) Reported-by: philip@philip-seeger.de Link: https://www.spinics.net/lists/linux-btrfs/msg96528.htmlReviewed-by:
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Josef Bacik authored
We noticed that we were having regular CG OOM kills in cases where there was still enough dirty pages to avoid OOM'ing. It turned out there's this corner case in btrfs's handling of range_cyclic where files that were being redirtied were not getting fully written out because of how we do range_cyclic writeback. We unconditionally were setting scanned = 1; the first time we found any pages in the inode. This isn't actually what we want, we want it to be set if we've scanned the entire file. For range_cyclic we could be starting in the middle or towards the end of the file, so we could write one page and then not write any of the other dirty pages in the file because we set scanned = 1. Fix this by not setting scanned = 1 if we find pages. The rules for setting scanned should be 1) !range_cyclic. In this case we have a specified range to write out. 2) range_cyclic && index == 0. In this case we've started at the beginning and there is no need to loop around a second time. 3) range_cyclic && we started at index > 0 and we've reached the end of the file without satisfying our nr_to_write. This patch fixes both of our writepages implementations to make sure these rules hold true. This fixed our over zealous CG OOMs in production. Fixes: d1310b2e ("Btrfs: Split the extent_map code into two parts") Signed-off-by:
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David Sterba authored
Dan's smatch tool reports fs/btrfs/file-item.c:295 btrfs_lookup_bio_sums() warn: should this be 'count == -1' which points to the while (count--) loop. With count == 0 the check itself could decrement it to -1. There's a WARN_ON a few lines below that has never been seen in practice though. It turns out that the value of page_bytes_left matches the count (by sectorsize multiples). The loop never reaches the state where count would go to -1, because page_bytes_left == 0 is found first and this breaks out. For clarity, use only plain check on count (and only for positive value), decrement safely inside the loop. Any other discrepancy after the whole bio list processing should be reported by the exising WARN_ON_ONCE as well. Reported-by:
Dan Carpenter <dan.carpenter@oracle.com> Reviewed-by:
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David Sterba authored
This is a leftover from recently removed bio scheduling framework. Fixes: ba8a9d07 ("Btrfs: delete the entire async bio submission framework") Reviewed-by:
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Johannes Thumshirn authored
btrfs_get_alloc_profile() is a simple wrapper over get_alloc_profile(). The only difference is btrfs_get_alloc_profile() is visible to other functions in btrfs while get_alloc_profile() is static and thus only visible to functions in block-group.c. Let's just fold get_alloc_profile() into btrfs_get_alloc_profile() to get rid of the unnecessary second function. Reviewed-by:
Johannes Thumshirn <jth@kernel.org> Reviewed-by:
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Dennis Zhou authored
From Dave's testing described below, it's possible to drive a file system to have bogus values of discardable_extents and _bytes. As btrfs_discard_calc_delay() is the only user of discardable_extents, we can correct here for any negative discardable_extents/discardable_bytes. The problem is not reliably reproducible. The workload that created it was based on linux git tree, switching between release tags, then everytihng deleted followed by a full rebalance. At this state the values of discardable_bytes was 16K and discardable_extents was -1, expected values 0 and 0. Repeating the workload again did not correct the bogus values so the offset seems to be stable once it happens. Reported-by:
Dennis Zhou <dennis@kernel.org> Signed-off-by:
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Dennis Zhou authored
Most callers of free_bitmap() only call it if bitmap_info->bytes is 0. However, there are certain cases where we may free the free space cache via __btrfs_remove_free_space_cache(). This exposes a path where free_bitmap() is called regardless. This may result in a bad accounting situation for discardable_bytes and discardable_extents. So, remove the stats and call btrfs_discard_update_discardable(). Signed-off-by:
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Dennis Zhou authored
It's less than ideal for small extents to eat into our extent budget, so force extents <= 32KB into the bitmaps save for the first handful. Reviewed-by:
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Dennis Zhou authored
Currently, there is no way for the free space cache to recover from being serviced by purely bitmaps because the extent threshold is set to 0 in recalculate_thresholds() when we surpass the metadata allowance. This adds a recovery mechanism by keeping large extents out of the bitmaps and increases the metadata upper bound to 64KB. The recovery mechanism bypasses this upper bound, thus making it a soft upper bound. But, with the bypass being 1MB or greater, it shouldn't add unbounded overhead. Reviewed-by:
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Dennis Zhou authored
Give a brief overview for how async discard is implemented. Reviewed-by:
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Dennis Zhou authored
Keep track of how much we are discarding and how often we are reusing with async discard. The discard_*_bytes values don't need any special protection because the work item provides the single threaded access. Reviewed-by:
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Dennis Zhou authored
As mentioned earlier, discarding data can be done either by issuing an explicit discard or implicitly by reusing the LBA. Metadata block_groups see much more frequent reuse due to well it being metadata. So instead of explicitly discarding metadata block_groups, just leave them be and let the latter implicit discarding be done for them. For mixed block_groups, block_groups which contain both metadata and data, we let them be as higher fragmentation is expected. Reviewed-by:
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Dennis Zhou authored
Non-block group destruction discarding currently only had a single list with no minimum discard length. This can lead to caravaning more meaningful discards behind a heavily fragmented block group. This adds support for multiple lists with minimum discard lengths to prevent the caravan effect. We promote block groups back up when we exceed the BTRFS_ASYNC_DISCARD_MAX_FILTER size, currently we support only 2 lists with filters of 1MB and 32KB respectively. Reviewed-by:
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Dennis Zhou authored
Expose max_discard_size as a tunable via sysfs and switch the current fixed maximum to the default value. Signed-off-by:
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Dennis Zhou authored
Throttle the maximum size of a discard so that we can provide an upper bound for the rate of async discard. While the block layer is able to split discards into the appropriate sized discards, we want to be able to account more accurately the rate at which we are consuming NCQ slots as well as limit the upper bound of work for a discard. Reviewed-by:
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Dennis Zhou authored
Provide the ability to rate limit based on kbps in addition to iops as additional guides for the target discard rate. The delay used ends up being max(kbps_delay, iops_delay). Signed-off-by:
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Dennis Zhou authored
An earlier patch keeps track of discardable_extents. These are undiscarded extents managed by the free space cache. Here, we will use this to dynamically calculate the discard delay interval. There are 3 rate to consider. The first is the target convergence rate, the rate to discard all discardable_extents over the BTRFS_DISCARD_TARGET_MSEC time frame. This is clamped by the lower limit, the iops limit or BTRFS_DISCARD_MIN_DELAY (1ms), and the upper limit, BTRFS_DISCARD_MAX_DELAY (1s). We reevaluate this delay every transaction commit. Reviewed-by:
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Dennis Zhou authored
Keep track of this metric so that we can understand how ahead or behind we are in discarding rate. This uses the same accounting method as discardable_extents, deltas between previous/current values and propagating them up. Signed-off-by:
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Dennis Zhou authored
The number of discardable extents will serve as the rate limiting metric for how often we should discard. This keeps track of discardable extents in the free space caches by maintaining deltas and propagating them to the global count. The deltas are calculated from 2 values stored in PREV and CURR entries, then propagated up to the global discard ctl. The current counter value becomes the previous counter value after update. Signed-off-by:
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Dennis Zhou authored
Setup base sysfs directory for discard stats + tunables. Reviewed-by:
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Dennis Zhou authored
Btrfs only allowed attributes to be exposed in debug/. Let's let other groups be created by making debug its own kobject. This also makes the per-fs debug options separate from the global features mount attributes. This seems to be needed as sysfs_create_files() requires const struct attribute * while sysfs_create_group() can take struct attribute *. This seems nicer as per file system, you'll probably use to_fs_info(). Reviewed-by:
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Dennis Zhou authored
We probably should call sysfs_remove_group() on debug/. Reviewed-by:
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Dennis Zhou authored
The prior two patches added discarding via a background workqueue. This just piggybacked off of the fstrim code to trim the whole block at once. Well inevitably this is worse performance wise and will aggressively overtrim. But it was nice to plumb the other infrastructure to keep the patches easier to review. This adds the real goal of this series which is discarding slowly (ie. a slow long running fstrim). The discarding is split into two phases, extents and then bitmaps. The reason for this is two fold. First, the bitmap regions overlap the extent regions. Second, discarding the extents first will let the newly trimmed bitmaps have the highest chance of coalescing when being readded to the free space cache. Reviewed-by:
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Dennis Zhou authored
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:
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