The local 'b' variable is only used to directly read values from passed
extent buffer. So eliminate it and directly use the input parameter.
Furthermore this shrinks the size of the following functions:
./scripts/bloat-o-meter ctree.orig fs/btrfs/ctree.o
add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-73 (-73)
Function old new delta
read_block_for_search.isra 876 871 -5
push_node_left 1112 1044 -68
Total: Before=50348, After=50275, chg -0.14%
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This function wraps the optimisation implemented by d7396f0735
("Btrfs: optimize key searches in btrfs_search_slot") however this
optimisation is really used in only one place - btrfs_search_slot.
Just open code the optimisation and also add a comment explaining how it
works since it's not clear just by looking at the code - the key point
here is it depends on an internal invariant that BTRFS' btree provides,
namely intermediate pointers always contain the key at slot0 at the
child node. So in the case of exact match we can safely assume that the
given key will always be in slot 0 on lower levels.
Furthermore this results in a reduction of btrfs_search_slot's size:
./scripts/bloat-o-meter ctree.orig fs/btrfs/ctree.o
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-75 (-75)
Function old new delta
btrfs_search_slot 2783 2708 -75
Total: Before=50423, After=50348, chg -0.15%
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The name BTRFS_ROOT_REF_COWS is not very clear about the meaning.
In fact, that bit can only be set to those trees:
- Subvolume roots
- Data reloc root
- Reloc roots for above roots
All other trees won't get this bit set. So just by the result, it is
obvious that, roots with this bit set can have tree blocks shared with
other trees. Either shared by snapshots, or by reloc roots (an special
snapshot created by relocation).
This patch will rename BTRFS_ROOT_REF_COWS to BTRFS_ROOT_SHAREABLE to
make it easier to understand, and update all comment mentioning
"reference counted" to follow the rename.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The bin search jumps over the extent buffer item keys, comparing
directly the bytes if the key is in one page, or storing it in a
temporary buffer in case it spans two pages.
The mapping start and length are obtained from map_private_extent_buffer,
which is heavy weight compared to what we need. We know the key size and
can find out the eb page in a simple way. For keys spanning two pages
the fallback read_extent_buffer is used.
The temporary variables are reduced and moved to the scope of use.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The token is supposed to cache the last page used by the set/get
helpers. In leaf_space_used the first and last items are accessed, it's
not likely they'd be on the same page so there's some overhead caused
updating the token address but not using it.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Now that all set/get helpers use the eb from the token, we don't need to
pass it to many btrfs_token_*/btrfs_set_token_* helpers, saving some
stack space.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
All callers pass the eb::level so we can get read it directly inside the
btrfs_bin_search and key_search.
This is inspired by the work of Marek in U-boot.
CC: Marek Behun <marek.behun@nic.cz>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There's an unnecessary indirection in the checksum definition table,
pointer and the string itself. The strings are short and the overall
size of one entry is now 24 bytes.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
All callers pass extent buffer start and length so the extent buffer
itself should work fine.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The helpers are related to locking so move them there, update comments.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Each new element added to the mod seq list is always appended to the list,
and each one gets a sequence number coming from a counter which gets
incremented everytime a new element is added to the list (or a new node
is added to the tree mod log rbtree). Therefore the element with the
lowest sequence number is always the first element in the list.
So just remove the list iteration at btrfs_put_tree_mod_seq() that
computes the minimum sequence number in the list and replace it with
a check for the first element's sequence number.
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>
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: bd989ba359 ("Btrfs: add tree modification log functions")
Fixes: 097b8a7c9e ("Btrfs: join tree mod log code with the code holding back delayed refs")
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When a tree mod log user no longer needs to use the tree it calls
btrfs_put_tree_mod_seq() to remove itself from the list of users and
delete all no longer used elements of the tree's red black tree, which
should be all elements with a sequence number less then our equals to
the caller's sequence number. However the logic is broken because it
can delete and free elements from the red black tree that have a
sequence number greater then the caller's sequence number:
1) At a point in time we have sequence numbers 1, 2, 3 and 4 in the
tree mod log;
2) The task which got assigned the sequence number 1 calls
btrfs_put_tree_mod_seq();
3) Sequence number 1 is deleted from the list of sequence numbers;
4) The current minimum sequence number is computed to be the sequence
number 2;
5) A task using sequence number 2 is at tree_mod_log_rewind() and gets
a pointer to one of its elements from the red black tree through
a call to tree_mod_log_search();
6) The task with sequence number 1 iterates the red black tree of tree
modification elements and deletes (and frees) all elements with a
sequence number less then or equals to 2 (the computed minimum sequence
number) - it ends up only leaving elements with sequence numbers of 3
and 4;
7) The task with sequence number 2 now uses the pointer to its element,
already freed by the other task, at __tree_mod_log_rewind(), resulting
in a use-after-free issue. When CONFIG_DEBUG_PAGEALLOC=y it produces
a trace like the following:
[16804.546854] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
[16804.547451] CPU: 0 PID: 28257 Comm: pool Tainted: G W 5.4.0-rc8-btrfs-next-51 #1
[16804.548059] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014
[16804.548666] RIP: 0010:rb_next+0x16/0x50
(...)
[16804.550581] RSP: 0018:ffffb948418ef9b0 EFLAGS: 00010202
[16804.551227] RAX: 6b6b6b6b6b6b6b6b RBX: ffff90e0247f6600 RCX: 6b6b6b6b6b6b6b6b
[16804.551873] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff90e0247f6600
[16804.552504] RBP: ffff90dffe0d4688 R08: 0000000000000001 R09: 0000000000000000
[16804.553136] R10: ffff90dffa4a0040 R11: 0000000000000000 R12: 000000000000002e
[16804.553768] R13: ffff90e0247f6600 R14: 0000000000001663 R15: ffff90dff77862b8
[16804.554399] FS: 00007f4b197ae700(0000) GS:ffff90e036a00000(0000) knlGS:0000000000000000
[16804.555039] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[16804.555683] CR2: 00007f4b10022000 CR3: 00000002060e2004 CR4: 00000000003606f0
[16804.556336] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[16804.556968] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[16804.557583] Call Trace:
[16804.558207] __tree_mod_log_rewind+0xbf/0x280 [btrfs]
[16804.558835] btrfs_search_old_slot+0x105/0xd00 [btrfs]
[16804.559468] resolve_indirect_refs+0x1eb/0xc70 [btrfs]
[16804.560087] ? free_extent_buffer.part.19+0x5a/0xc0 [btrfs]
[16804.560700] find_parent_nodes+0x388/0x1120 [btrfs]
[16804.561310] btrfs_check_shared+0x115/0x1c0 [btrfs]
[16804.561916] ? extent_fiemap+0x59d/0x6d0 [btrfs]
[16804.562518] extent_fiemap+0x59d/0x6d0 [btrfs]
[16804.563112] ? __might_fault+0x11/0x90
[16804.563706] do_vfs_ioctl+0x45a/0x700
[16804.564299] ksys_ioctl+0x70/0x80
[16804.564885] ? trace_hardirqs_off_thunk+0x1a/0x20
[16804.565461] __x64_sys_ioctl+0x16/0x20
[16804.566020] do_syscall_64+0x5c/0x250
[16804.566580] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[16804.567153] RIP: 0033:0x7f4b1ba2add7
(...)
[16804.568907] RSP: 002b:00007f4b197adc88 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[16804.569513] RAX: ffffffffffffffda RBX: 00007f4b100210d8 RCX: 00007f4b1ba2add7
[16804.570133] RDX: 00007f4b100210d8 RSI: 00000000c020660b RDI: 0000000000000003
[16804.570726] RBP: 000055de05a6cfe0 R08: 0000000000000000 R09: 00007f4b197add44
[16804.571314] R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4b197add48
[16804.571905] R13: 00007f4b197add40 R14: 00007f4b100210d0 R15: 00007f4b197add50
(...)
[16804.575623] ---[ end trace 87317359aad4ba50 ]---
Fix this by making btrfs_put_tree_mod_seq() skip deletion of elements that
have a sequence number equals to the computed minimum sequence number, and
not just elements with a sequence number greater then that minimum.
Fixes: bd989ba359 ("Btrfs: add tree modification log functions")
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently all the checksum algorithms generate a fixed size digest size
and we use it. The on-disk format can hold up to BTRFS_CSUM_SIZE bytes
and BLAKE2b produces digest of 512 bits by default. We can't do that and
will use the blake2b-256, this needs to be passed to the crypto API.
Separate that from the base algorithm name and add a member to request
specific driver, in this case with the digest size.
The only place that uses the driver name is the crypto API setup.
Signed-off-by: David Sterba <dsterba@suse.com>
Export supported checksum algorithms via sysfs in the list of static
features:
/sys/fs/btrfs/features/supported_checksums
Space spearated list of checksum algorithm names.
Co-developed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Add sha256 to the list of possible checksumming algorithms used by BTRFS.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Add xxhash64 to the list of possible checksumming algorithms used by
BTRFS.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The helper is trivial and we can understand what the atomic_inc on
something named refs does.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The attribute is more relaxed than const and the functions could
dereference pointers, as long as the observable state is not changed. We
do have such functions, based on -Wsuggest-attribute=pure .
The visible effects of this patch are negligible, there are differences
in the assembly but hard to summarize.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The function belongs to the family of locking functions, so move it
there. The 'noinline' keyword is dropped as it's now an exported
function that does not need it.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The function belongs to the family of locking functions, so move it
there. The 'noinline' keyword is dropped as it's now an exported
function that does not need it.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The following comment shows up in btrfs_search_slot() with out much
sense:
/*
* setup the path here so we can release it under lock
* contention with the cow code
*/
if (cow) {
/* code touching path->lock[] is far away from here */
}
This comment hasn't been cleaned up after the relevant code has been
removed.
The original code is introduced in commit 65b51a009e
("btrfs_search_slot: reduce lock contention by cowing in two stages"):
+
+ /*
+ * setup the path here so we can release it under lock
+ * contention with the cow code
+ */
+ p->nodes[level] = b;
+ if (!p->skip_locking)
+ p->locks[level] = 1;
+
But in current code, we have different timing for modifying path lock,
so just remove the comment.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Similar to btrfs_search_slot() done in previous patch, make a shortcut
for the level 0 case and allow to reduce indentation for the remaining
case.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
In btrfs_search_slot(), we something like:
if (level != 0) {
/* Do search inside tree nodes*/
} else {
/* Do search inside tree leaves */
goto done;
}
This caused extra indent for tree node search code. Change it to
something like:
if (level == 0) {
/* Do search inside tree leaves */
goto done'
}
/* Do search inside tree nodes */
So we have more space to maneuver our code, this is especially useful as
the tree nodes search code is more complex than the leaves search code.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Those function are simple boolean predicates there is no need to assign
their return values to interim variables. Use them directly as
predicates. No functional changes.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Create a structure to encode the type and length for the known on-disk
checksums. This makes it easier to add new checksums later.
The structure and helpers are moved from ctree.h so they don't occupy
space in all headers including ctree.h. This save some space in the
final object.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Further simplifaction of the get/set helpers is possible when the token
is uniquely tied to an extent buffer. A condition and an assignment can
be avoided.
The initializations are moved closer to the first use when the extent
buffer is valid. There's one exception in __push_leaf_left where the
token is reused.
Signed-off-by: David Sterba <dsterba@suse.com>
Send is the only user of tree_compare, we can move it there along with
the other helpers and definitions.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Preparatory work for code that will be moved out of ctree and uses this
function.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
extent-tree.c has a find_next_key that just walks up the path to find
the next key, but it is used for both the caching stuff and the snapshot
delete stuff. The snapshot deletion stuff is special so it can't really
use btrfs_find_next_key, but the caching thread stuff can. We just need
to fix btrfs_find_next_key to deal with ->skip_locking and then it works
exactly the same as the private find_next_key helper.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The tree is going to be modified so it must be the exclusive lock.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
