CodingStyle chapter 2:
"[...] never break user-visible strings such as printk messages,
because that breaks the ability to grep for them."
This patch unsplits user-visible strings.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
commit 909c3a22da (Btrfs: fix loading of orphan roots leading to BUG_ON)
avoids the BUG_ON but can add an aliased root to the dead_roots list or
leak the root.
Since we've already been loading roots into the radix tree, we should
use it before looking the root up on disk.
Cc: <stable@vger.kernel.org> # 4.5
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
__btrfs_abort_transaction doesn't use its root parameter except to
obtain an fs_info pointer. We can obtain that from trans->root->fs_info
for now and from trans->fs_info in a later patch.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_std_error() handles errors, puts FS into readonly mode
(as of now). So its good idea to rename it to btrfs_handle_fs_error().
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ edit changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
Pull btrfs updates from Chris Mason:
"We have a good sized cleanup of our internal read ahead code, and the
first series of commits from Chandan to enable PAGE_SIZE > sectorsize
Otherwise, it's a normal series of cleanups and fixes, with many
thanks to Dave Sterba for doing most of the patch wrangling this time"
* 'for-linus-4.6' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs: (82 commits)
btrfs: make sure we stay inside the bvec during __btrfs_lookup_bio_sums
btrfs: Fix misspellings in comments.
btrfs: Print Warning only if ENOSPC_DEBUG is enabled
btrfs: scrub: silence an uninitialized variable warning
btrfs: move btrfs_compression_type to compression.h
btrfs: rename btrfs_print_info to btrfs_print_mod_info
Btrfs: Show a warning message if one of objectid reaches its highest value
Documentation: btrfs: remove usage specific information
btrfs: use kbasename in btrfsic_mount
Btrfs: do not collect ordered extents when logging that inode exists
Btrfs: fix race when checking if we can skip fsync'ing an inode
Btrfs: fix listxattrs not listing all xattrs packed in the same item
Btrfs: fix deadlock between direct IO reads and buffered writes
Btrfs: fix extent_same allowing destination offset beyond i_size
Btrfs: fix file loss on log replay after renaming a file and fsync
Btrfs: fix unreplayable log after snapshot delete + parent dir fsync
Btrfs: fix lockdep deadlock warning due to dev_replace
btrfs: drop unused argument in btrfs_ioctl_get_supported_features
btrfs: add GET_SUPPORTED_FEATURES to the control device ioctls
btrfs: change max_inline default to 2048
...
When looking for orphan roots during mount we can end up hitting a
BUG_ON() (at root-item.c:btrfs_find_orphan_roots()) if a log tree is
replayed and qgroups are enabled. This is because after a log tree is
replayed, a transaction commit is made, which triggers qgroup extent
accounting which in turn does backref walking which ends up reading and
inserting all roots in the radix tree fs_info->fs_root_radix, including
orphan roots (deleted snapshots). So after the log tree is replayed, when
finding orphan roots we hit the BUG_ON with the following trace:
[118209.182438] ------------[ cut here ]------------
[118209.183279] kernel BUG at fs/btrfs/root-tree.c:314!
[118209.184074] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[118209.185123] Modules linked in: btrfs dm_flakey dm_mod crc32c_generic ppdev xor raid6_pq evdev sg parport_pc parport acpi_cpufreq tpm_tis tpm psmouse
processor i2c_piix4 serio_raw pcspkr i2c_core button loop autofs4 ext4 crc16 mbcache jbd2 sd_mod sr_mod cdrom ata_generic virtio_scsi ata_piix libata
virtio_pci virtio_ring virtio scsi_mod e1000 floppy [last unloaded: btrfs]
[118209.186318] CPU: 14 PID: 28428 Comm: mount Tainted: G W 4.5.0-rc5-btrfs-next-24+ #1
[118209.186318] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS by qemu-project.org 04/01/2014
[118209.186318] task: ffff8801ec131040 ti: ffff8800af34c000 task.ti: ffff8800af34c000
[118209.186318] RIP: 0010:[<ffffffffa04237d7>] [<ffffffffa04237d7>] btrfs_find_orphan_roots+0x1fc/0x244 [btrfs]
[118209.186318] RSP: 0018:ffff8800af34faa8 EFLAGS: 00010246
[118209.186318] RAX: 00000000ffffffef RBX: 00000000ffffffef RCX: 0000000000000001
[118209.186318] RDX: 0000000080000000 RSI: 0000000000000001 RDI: 00000000ffffffff
[118209.186318] RBP: ffff8800af34fb08 R08: 0000000000000001 R09: 0000000000000000
[118209.186318] R10: ffff8800af34f9f0 R11: 6db6db6db6db6db7 R12: ffff880171b97000
[118209.186318] R13: ffff8801ca9d65e0 R14: ffff8800afa2e000 R15: 0000160000000000
[118209.186318] FS: 00007f5bcb914840(0000) GS:ffff88023edc0000(0000) knlGS:0000000000000000
[118209.186318] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[118209.186318] CR2: 00007f5bcaceb5d9 CR3: 00000000b49b5000 CR4: 00000000000006e0
[118209.186318] Stack:
[118209.186318] fffffbffffffffff 010230ffffffffff 0101000000000000 ff84000000000000
[118209.186318] fbffffffffffffff 30ffffffffffffff 0000000000000101 ffff880082348000
[118209.186318] 0000000000000000 ffff8800afa2e000 ffff8800afa2e000 0000000000000000
[118209.186318] Call Trace:
[118209.186318] [<ffffffffa042e2db>] open_ctree+0x1e37/0x21b9 [btrfs]
[118209.186318] [<ffffffffa040a753>] btrfs_mount+0x97e/0xaed [btrfs]
[118209.186318] [<ffffffff8108e1c0>] ? trace_hardirqs_on+0xd/0xf
[118209.186318] [<ffffffff8117b87e>] mount_fs+0x67/0x131
[118209.186318] [<ffffffff81192d2b>] vfs_kern_mount+0x6c/0xde
[118209.186318] [<ffffffffa0409f81>] btrfs_mount+0x1ac/0xaed [btrfs]
[118209.186318] [<ffffffff8108e1c0>] ? trace_hardirqs_on+0xd/0xf
[118209.186318] [<ffffffff8108c26b>] ? lockdep_init_map+0xb9/0x1b3
[118209.186318] [<ffffffff8117b87e>] mount_fs+0x67/0x131
[118209.186318] [<ffffffff81192d2b>] vfs_kern_mount+0x6c/0xde
[118209.186318] [<ffffffff81195637>] do_mount+0x8a6/0x9e8
[118209.186318] [<ffffffff8119598d>] SyS_mount+0x77/0x9f
[118209.186318] [<ffffffff81493017>] entry_SYSCALL_64_fastpath+0x12/0x6b
[118209.186318] Code: 64 00 00 85 c0 89 c3 75 24 f0 41 80 4c 24 20 20 49 8b bc 24 f0 01 00 00 4c 89 e6 e8 e8 65 00 00 85 c0 89 c3 74 11 83 f8 ef 75 02 <0f> 0b
4c 89 e7 e8 da 72 00 00 eb 1c 41 83 bc 24 00 01 00 00 00
[118209.186318] RIP [<ffffffffa04237d7>] btrfs_find_orphan_roots+0x1fc/0x244 [btrfs]
[118209.186318] RSP <ffff8800af34faa8>
[118209.230735] ---[ end trace 83938f987d85d477 ]---
So fix this by not treating the error -EEXIST, returned when attempting
to insert a root already inserted by the backref walking code, as an error.
The following test case for xfstests reproduces the bug:
seq=`basename $0`
seqres=$RESULT_DIR/$seq
echo "QA output created by $seq"
tmp=/tmp/$$
status=1 # failure is the default!
trap "_cleanup; exit \$status" 0 1 2 3 15
_cleanup()
{
_cleanup_flakey
cd /
rm -f $tmp.*
}
# get standard environment, filters and checks
. ./common/rc
. ./common/filter
. ./common/dmflakey
# real QA test starts here
_supported_fs btrfs
_supported_os Linux
_require_scratch
_require_dm_target flakey
_require_metadata_journaling $SCRATCH_DEV
rm -f $seqres.full
_scratch_mkfs >>$seqres.full 2>&1
_init_flakey
_mount_flakey
_run_btrfs_util_prog quota enable $SCRATCH_MNT
# Create 2 directories with one file in one of them.
# We use these just to trigger a transaction commit later, moving the file from
# directory a to directory b and doing an fsync against directory a.
mkdir $SCRATCH_MNT/a
mkdir $SCRATCH_MNT/b
touch $SCRATCH_MNT/a/f
sync
# Create our test file with 2 4K extents.
$XFS_IO_PROG -f -s -c "pwrite -S 0xaa 0 8K" $SCRATCH_MNT/foobar | _filter_xfs_io
# Create a snapshot and delete it. This doesn't really delete the snapshot
# immediately, just makes it inaccessible and invisible to user space, the
# snapshot is deleted later by a dedicated kernel thread (cleaner kthread)
# which is woke up at the next transaction commit.
# A root orphan item is inserted into the tree of tree roots, so that if a
# power failure happens before the dedicated kernel thread does the snapshot
# deletion, the next time the filesystem is mounted it resumes the snapshot
# deletion.
_run_btrfs_util_prog subvolume snapshot $SCRATCH_MNT $SCRATCH_MNT/snap
_run_btrfs_util_prog subvolume delete $SCRATCH_MNT/snap
# Now overwrite half of the extents we wrote before. Because we made a snapshpot
# before, which isn't really deleted yet (since no transaction commit happened
# after we did the snapshot delete request), the non overwritten extents get
# referenced twice, once by the default subvolume and once by the snapshot.
$XFS_IO_PROG -c "pwrite -S 0xbb 4K 8K" $SCRATCH_MNT/foobar | _filter_xfs_io
# Now move file f from directory a to directory b and fsync directory a.
# The fsync on the directory a triggers a transaction commit (because a file
# was moved from it to another directory) and the file fsync leaves a log tree
# with file extent items to replay.
mv $SCRATCH_MNT/a/f $SCRATCH_MNT/a/b
$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/a
$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/foobar
echo "File digest before power failure:"
md5sum $SCRATCH_MNT/foobar | _filter_scratch
# Now simulate a power failure and mount the filesystem to replay the log tree.
# After the log tree was replayed, we used to hit a BUG_ON() when processing
# the root orphan item for the deleted snapshot. This is because when processing
# an orphan root the code expected to be the first code inserting the root into
# the fs_info->fs_root_radix radix tree, while in reallity it was the second
# caller attempting to do it - the first caller was the transaction commit that
# took place after replaying the log tree, when updating the qgroup counters.
_flakey_drop_and_remount
echo "File digest before after failure:"
# Must match what he got before the power failure.
md5sum $SCRATCH_MNT/foobar | _filter_scratch
_unmount_flakey
status=0
exit
Fixes: 2d9e977610 ("Btrfs: use btrfs_get_fs_root in resolve_indirect_ref")
Cc: stable@vger.kernel.org # 4.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
CURRENT_TIME macro is not appropriate for filesystems as it
doesn't use the right granularity for filesystem timestamps.
Use current_fs_time() instead.
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: linux-btrfs@vger.kernel.org
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
old_len is used to store the return value of btrfs_item_size_nr().
The return value of btrfs_item_size_nr() is of type u32.
To improve code correctness and avoid mixing signed and unsigned
integers I've changed old_len to be of type u32 as well.
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Alexandru Moise <00moses.alexander00@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Convert the simple cases, not all functions provide a way to reach the
fs_info. Also skipped debugging messages (print-tree, integrity
checker and pr_debug) and messages that are printed from possibly
unfinished mount.
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_error() and btrfs_std_error() does the same thing
and calls _btrfs_std_error(), so consolidate them together.
And the main motivation is that btrfs_error() is closely
named with btrfs_err(), one handles error action the other
is to log the error, so don't closely name them.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Suggested-by: David Sterba <dsterba@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
PTR_RET is deprecated. Use PTR_ERR_OR_ZERO instead. While at it
also include missing err.h header.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Convert all applicable cases of printk and pr_* to the btrfs_* macros.
Fix all uses of the BTRFS prefix.
Signed-off-by: Frank Holton <fholton@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
This patch is the second step in bootstrapping the btrfs_find_item
interface. The btrfs_find_root_ref() is similar to the former
__inode_info(); it accepts four of its parameters, and duplicates the
first half of its functionality.
Replace the one former call to btrfs_find_root_ref() with a call to
btrfs_find_item(), along with the defined key type that was used
internally by btrfs_find_root ref, and a null found key. In
btrfs_find_item(), add a test for the null key at the place where
the functionality of btrfs_find_root_ref() ends; btrfs_find_item()
then returns if the test passes. Finally, remove btrfs_find_root_ref().
Signed-off-by: Kelley Nielsen <kelleynnn@gmail.com>
Suggested-by: Zach Brown <zab@redhat.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <clm@fb.com>
Now we don't drop all the deleted snapshots/subvolumes before the space
balance. It means we have to relocate the space which is held by the dead
snapshots/subvolumes. So we must into them into fs radix tree, or we would
forget to commit the change of them when doing transaction commit, and it
would corrupt the metadata.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
u64 is "unsigned long long" on all architectures now, so there's no need to
cast it when formatting it using the "ll" length modifier.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
Cc: Josef Bacik <jbacik@fusionio.com>
Cc: Chris Mason <chris.mason@fusionio.com>
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
Some codes still use the cpu_to_lexx instead of the
BTRFS_SETGET_STACK_FUNCS declared in ctree.h.
Also added some BTRFS_SETGET_STACK_FUNCS for btrfs_header btrfs_timespec
and other structures.
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: Miao Xie <miaoxie@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
I hit a weird problem were my root item had been deleted but the orphan item had
not. This isn't necessarily a problem, but it keeps the file system from being
mounted. To fix this we just need to axe the orphan item if we can't find the
fs root when we're putting them altogether. With this patch I was able to
successfully mount my file system. Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
There are several functions whose code is similar, such as
btrfs_find_last_root()
btrfs_read_fs_root_no_radix()
Besides that, some functions are invoked twice, it is unnecessary,
for example, we are sure that all roots which is found in
btrfs_find_orphan_roots()
have their orphan items, so it is unnecessary to check the orphan
item again.
So cleanup it.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Originally root_times_lock was introduced as part of send/receive
code however newly developed patch to label the subvol reused
the same lock, so renaming it for a meaningful name.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
Call btrfs_abort_transaction as early as possible when an error
condition is detected, that way the line number reported is useful
and we're not clueless anymore which error path led to the abort.
Signed-off-by: David Sterba <dsterba@suse.cz>
"trans->transid" is cpu endian but we want to store the data as little
endian. "item->ctime.nsec" is only 32 bits, not 64.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
This patch introduces uuids for subvolumes. Each
subvolume has it's own uuid. In case it was snapshotted,
it also contains parent_uuid. In case it was received,
it also contains received_uuid.
It also introduces subvolume ctime/otime/stime/rtime. The
first two are comparable to the times found in inodes. otime
is the origin/creation time and ctime is the change time.
stime/rtime are only valid on received subvolumes.
stime is the time of the subvolume when it was
sent. rtime is the time of the subvolume when it was
received.
Additionally to the times, we have a transid for each
time. They are updated at the same place as the times.
btrfs receive uses stransid and rtransid to find out
if a received subvolume changed in the meantime.
If an older kernel mounts a filesystem with the
extented fields, all fields become invalid. The next
mount with a new kernel will detect this and reset the
fields.
Signed-off-by: Alexander Block <ablock84@googlemail.com>
Reviewed-by: David Sterba <dave@jikos.cz>
Reviewed-by: Arne Jansen <sensille@gmx.net>
Reviewed-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Reviewed-by: Alex Lyakas <alex.bolshoy.btrfs@gmail.com>
btrfs currently handles most errors with BUG_ON. This patch is a work-in-
progress but aims to handle most errors other than internal logic
errors and ENOMEM more gracefully.
This iteration prevents most crashes but can run into lockups with
the page lock on occasion when the timing "works out."
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
btrfs_update_root BUG's when it can't alloc a path, yet it can recover
from a search error. This patch returns -ENOMEM instead.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
This is fairly trivial - btrfs_set_root_node() - always returns zero so we
can just make it void. All callers ignore the return code now anyway. I
also made sure to check that none of the functions that
btrfs_set_root_node() calls returns an error that we might have needed to
catch and pass back.
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
The error code is returned instead of calling BUG_ON when
btrfs_del_item returns the error.
Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Remove static and global declarations and/or definitions. Reduces size
of btrfs.ko by ~3.4kB.
text data bss dec hex filename
402081 7464 200 409745 64091 btrfs.ko.base
398620 7144 200 405964 631cc btrfs.ko.remove-all
Signed-off-by: David Sterba <dsterba@suse.cz>
parameter tree root it's not used since commit
5f39d397df ("Btrfs: Create extent_buffer
interface for large blocksizes")
Signed-off-by: David Sterba <dsterba@suse.cz>
root_item->flags and root_item->byte_limit are not initialized when
a subvolume is created. This bug is not revealed until we added
readonly snapshot support - now you mount a btrfs filesystem and you
may find the subvolumes in it are readonly.
To work around this problem, we steal a bit from root_item->inode_item->flags,
and use it to indicate if those fields have been properly initialized.
When we read a tree root from disk, we check if the bit is set, and if
not we'll set the flag and initialize the two fields of the root item.
Reported-by: Andreas Philipp <philipp.andreas@gmail.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Tested-by: Andreas Philipp <philipp.andreas@gmail.com>
cc: stable@kernel.org
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This patch changes some BUG_ON() to the error return.
(but, most callers still use BUG_ON())
Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
These are all the cases where a variable is set, but not read which are
not bugs as far as I can see, but simply leftovers.
Still needs more review.
Found by gcc 4.6's new warnings
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
If btrfs_ioctl_snap_destroy() deletes a snapshot but finishes
with end_transaction(), the cleaner kthread may come in and
drop the root in the same transaction. If that's the case, the
root's refs still == 1 in the tree when btrfs_del_root() deletes
the item, because commit_fs_roots() hasn't updated it yet (that
happens during the commit).
This wasn't a problem before only because
btrfs_ioctl_snap_destroy() would commit the transaction before dropping
the dentry reference, so the dead root wouldn't get queued up until
after the fs root item was updated in the btree.
Since it is not an error to drop the root reference and the root in the
same transaction, just drop the BUG_ON() in btrfs_del_root().
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
We don't need to call btrfs_release_path because btrfs_free_path will do
that for us.
Signed-off-by: Li Dongyang <Jerry87905@gmail.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This patch adds snapshot/subvolume destroy ioctl. A subvolume that isn't being
used and doesn't contains links to other subvolumes can be destroyed.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
btrfs allows subvolumes and snapshots anywhere in the directory tree.
If we snapshot a subvolume that contains a link to other subvolume
called subvolA, subvolA can be accessed through both the original
subvolume and the snapshot. This is similar to creating hard link to
directory, and has the very similar problems.
The aim of this patch is enforcing there is only one access point to
each subvolume. Only the first directory entry (the one added when
the subvolume/snapshot was created) is treated as valid access point.
The first directory entry is distinguished by checking root forward
reference. If the corresponding root forward reference is missing,
we know the entry is not the first one.
This patch also adds snapshot/subvolume rename support, the code
allows rename subvolume link across subvolumes.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit introduces a new kind of back reference for btrfs metadata.
Once a filesystem has been mounted with this commit, IT WILL NO LONGER
BE MOUNTABLE BY OLDER KERNELS.
When a tree block in subvolume tree is cow'd, the reference counts of all
extents it points to are increased by one. At transaction commit time,
the old root of the subvolume is recorded in a "dead root" data structure,
and the btree it points to is later walked, dropping reference counts
and freeing any blocks where the reference count goes to 0.
The increments done during cow and decrements done after commit cancel out,
and the walk is a very expensive way to go about freeing the blocks that
are no longer referenced by the new btree root. This commit reduces the
transaction overhead by avoiding the need for dead root records.
When a non-shared tree block is cow'd, we free the old block at once, and the
new block inherits old block's references. When a tree block with reference
count > 1 is cow'd, we increase the reference counts of all extents
the new block points to by one, and decrease the old block's reference count by
one.
This dead tree avoidance code removes the need to modify the reference
counts of lower level extents when a non-shared tree block is cow'd.
But we still need to update back ref for all pointers in the block.
This is because the location of the block is recorded in the back ref
item.
We can solve this by introducing a new type of back ref. The new
back ref provides information about pointer's key, level and in which
tree the pointer lives. This information allow us to find the pointer
by searching the tree. The shortcoming of the new back ref is that it
only works for pointers in tree blocks referenced by their owner trees.
This is mostly a problem for snapshots, where resolving one of these
fuzzy back references would be O(number_of_snapshots) and quite slow.
The solution used here is to use the fuzzy back references in the common
case where a given tree block is only referenced by one root,
and use the full back references when multiple roots have a reference
on a given block.
This commit adds per subvolume red-black tree to keep trace of cached
inodes. The red-black tree helps the balancing code to find cached
inodes whose inode numbers within a given range.
This commit improves the balancing code by introducing several data
structures to keep the state of balancing. The most important one
is the back ref cache. It caches how the upper level tree blocks are
referenced. This greatly reduce the overhead of checking back ref.
The improved balancing code scales significantly better with a large
number of snapshots.
This is a very large commit and was written in a number of
pieces. But, they depend heavily on the disk format change and were
squashed together to make sure git bisect didn't end up in a
bad state wrt space balancing or the format change.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Shut up various sparse warnings about symbols that should be either
static or have their declarations in scope.
Signed-off-by: Christoph Hellwig <hch@lst.de>
For a directory tree:
/mnt/subvolA/subvolB
btrfsctl -s /mnt/subvolA/subvolB /mnt
Will create a directory loop with subvolA under subvolB. This
commit uses the forward refs for each subvol and snapshot to error out
before creating the loop.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
