The individual testcases for extent maps do not return an error on
allocation failures. This is not a big problem as the allocation don't
fail in general but there are functional tests handled with ASSERTS.
This makes tests dependent on them and it's not reliable.
This patch adds the allocation failure handling and allows for the
conversion of the asserts to proper error handling and reporting.
Signed-off-by: David Sterba <dsterba@suse.com>
Allocation of main objects like fs_info or extent buffers is in each
test so let's simplify and unify the error messages to a table and add a
convenience helper.
Signed-off-by: David Sterba <dsterba@suse.com>
For better diagnostics print the file name and line to locate the
errors. Sample output:
[ 9.052924] BTRFS: selftest: fs/btrfs/tests/extent-io-tests.c:283 offset bits do not match
Signed-off-by: David Sterba <dsterba@suse.com>
The fs_info is not freed at the end of the function and leaks. The
function is called twice so there can be up to 2x sizeof(struct
btrfs_fs_info) of leaked memory. Fortunatelly this affects only testing
builds, the size could be 16k with several debugging features enabled.
Signed-off-by: David Sterba <dsterba@suse.com>
Just add one extra line to show when the corruption is detected.
Currently only read time detection is possible.
The planned distinguish line would be:
read time:
<detailed report>
block=XXXXX read time tree block corruption detected
write time:
<detailed report>
block=XXXXX write time tree block corruption detected
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We've been seeing the following sporadically throughout our fleet
panic: kernel BUG at fs/btrfs/relocation.c:4584!
netversion: 5.0-0
Backtrace:
#0 [ffffc90003adb880] machine_kexec at ffffffff81041da8
#1 [ffffc90003adb8c8] __crash_kexec at ffffffff8110396c
#2 [ffffc90003adb988] crash_kexec at ffffffff811048ad
#3 [ffffc90003adb9a0] oops_end at ffffffff8101c19a
#4 [ffffc90003adb9c0] do_trap at ffffffff81019114
#5 [ffffc90003adba00] do_error_trap at ffffffff810195d0
#6 [ffffc90003adbab0] invalid_op at ffffffff81a00a9b
[exception RIP: btrfs_reloc_cow_block+692]
RIP: ffffffff8143b614 RSP: ffffc90003adbb68 RFLAGS: 00010246
RAX: fffffffffffffff7 RBX: ffff8806b9c32000 RCX: ffff8806aad00690
RDX: ffff880850b295e0 RSI: ffff8806b9c32000 RDI: ffff88084f205bd0
RBP: ffff880849415000 R8: ffffc90003adbbe0 R9: ffff88085ac90000
R10: ffff8805f7369140 R11: 0000000000000000 R12: ffff880850b295e0
R13: ffff88084f205bd0 R14: 0000000000000000 R15: 0000000000000000
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
#7 [ffffc90003adbbb0] __btrfs_cow_block at ffffffff813bf1cd
#8 [ffffc90003adbc28] btrfs_cow_block at ffffffff813bf4b3
#9 [ffffc90003adbc78] btrfs_search_slot at ffffffff813c2e6c
The way relocation moves data extents is by creating a reloc inode and
preallocating extents in this inode and then copying the data into these
preallocated extents. Once we've done this for all of our extents,
we'll write out these dirty pages, which marks the extent written, and
goes into btrfs_reloc_cow_block(). From here we get our current
reloc_control, which _should_ match the reloc_control for the current
block group we're relocating.
However if we get an ENOSPC in this path at some point we'll bail out,
never initiating writeback on this inode. Not a huge deal, unless we
happen to be doing relocation on a different block group, and this block
group is now rc->stage == UPDATE_DATA_PTRS. This trips the BUG_ON() in
btrfs_reloc_cow_block(), because we expect to be done modifying the data
inode. We are in fact done modifying the metadata for the data inode
we're currently using, but not the one from the failed block group, and
thus we BUG_ON().
(This happens when writeback finishes for extents from the previous
group, when we are at btrfs_finish_ordered_io() which updates the data
reloc tree (inode item, drops/adds extent items, etc).)
Fix this by writing out the reloc data inode always, and then breaking
out of the loop after that point to keep from tripping this BUG_ON()
later.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
[ add note from Filipe ]
Signed-off-by: David Sterba <dsterba@suse.com>
The uptodate parameter of btrfs_writepage_endio_finish_ordered is used
to signal whether an error has occured while writing the given page.
0 signals an error, which is propagated to callees and 1 signifies
success. In end_compressed_bio_write the ->bi_status is checked and
based on it either BLK_STS_OK (0) or BLK_STS_NOTSUPP (1) are used. While
from functional point of view this is ok it's a for the poor reader of
the code, since the block layer values are conflated with the semantics
of the parameter.
Just use plain 0 or 1. 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>
We can only get <=0 from extent_write_cache_pages, add an ASSERT() for
it just in case.
Then instead of submitting the write bio even if we got some error,
check the return value first.
If we have already hit some error, just clean up the corrupted or
half-baked bio, and return error.
If there is no error so far, then call flush_write_bio() and return the
result.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This function needs some extra checks on locked pages and eb. For error
handling we need to unlock locked pages and the eb.
There is a rare >0 return value branch, where all pages get locked
while write bio is not flushed.
Thankfully it's handled by the only caller, btree_write_cache_pages(),
as later write_one_eb() call will trigger submit_one_bio(). So there
shouldn't be any problem.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We can only get @ret <= 0. Add an ASSERT() for it just in case.
Then, instead of submitting the write bio even we got some error, check
the return value first.
If we have already hit some error, just clean up the corrupted or
half-baked bio, and return error.
If there is no error so far, then call flush_write_bio() and return the
result.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Since __extent_writepage() will no longer return >0 value,
(ret == AOP_WRITEPAGE_ACTIVATE) will never be true.
Kill that dead branch.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In btree_write_cache_pages(), we can only get @ret <= 0.
Add an ASSERT() for it just in case.
Then instead of submitting the write bio even we got some error, check
the return value first.
If we have already hit some error, just clean up the corrupted or
half-baked bio, and return error.
If there is no error so far, then call flush_write_bio() and return the
result.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Since now flush_write_bio() could return error, kill the BUG_ON() first.
Then don't call flush_write_bio() unconditionally, instead we check the
return value from __extent_writepage() first.
If __extent_writepage() fails, we do cleanup, and return error without
submitting the possible corrupted or half-baked bio.
If __extent_writepage() successes, then we call flush_write_bio() and
return the result.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We have a BUG_ON() in flush_write_bio() to handle the return value of
submit_one_bio().
Move the BUG_ON() one level up to all its callers.
This patch will introduce temporary variable, @flush_ret to keep code
change minimal in this patch. That variable will be cleaned up when
enhancing the error handling later.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We have internal report of strange transaction abort due to EUCLEAN
without any error message.
Since error message inside verify_level_key() is only enabled for
CONFIG_BTRFS_DEBUG, the error message won't be printed on most builds.
This patch will make the error message mandatory, so when problem
happens we know what's causing the problem.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
When reading a file from a fuzzed image, kernel can panic like:
BTRFS warning (device loop0): csum failed root 5 ino 270 off 0 csum 0x98f94189 expected csum 0x00000000 mirror 1
assertion failed: !memcmp_extent_buffer(b, &disk_key, offsetof(struct btrfs_leaf, items[0].key), sizeof(disk_key)), file: fs/btrfs/ctree.c, line: 2544
------------[ cut here ]------------
kernel BUG at fs/btrfs/ctree.h:3500!
invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
RIP: 0010:btrfs_search_slot.cold.24+0x61/0x63 [btrfs]
Call Trace:
btrfs_lookup_csum+0x52/0x150 [btrfs]
__btrfs_lookup_bio_sums+0x209/0x640 [btrfs]
btrfs_submit_bio_hook+0x103/0x170 [btrfs]
submit_one_bio+0x59/0x80 [btrfs]
extent_read_full_page+0x58/0x80 [btrfs]
generic_file_read_iter+0x2f6/0x9d0
__vfs_read+0x14d/0x1a0
vfs_read+0x8d/0x140
ksys_read+0x52/0xc0
do_syscall_64+0x60/0x210
entry_SYSCALL_64_after_hwframe+0x49/0xbe
[CAUSE]
The fuzzed image has a corrupted leaf whose first key doesn't match its
parent:
checksum tree key (CSUM_TREE ROOT_ITEM 0)
node 29741056 level 1 items 14 free 107 generation 19 owner CSUM_TREE
fs uuid 3381d111-94a3-4ac7-8f39-611bbbdab7e6
chunk uuid 9af1c3c7-2af5-488b-8553-530bd515f14c
...
key (EXTENT_CSUM EXTENT_CSUM 79691776) block 29761536 gen 19
leaf 29761536 items 1 free space 1726 generation 19 owner CSUM_TREE
leaf 29761536 flags 0x1(WRITTEN) backref revision 1
fs uuid 3381d111-94a3-4ac7-8f39-611bbbdab7e6
chunk uuid 9af1c3c7-2af5-488b-8553-530bd515f14c
item 0 key (EXTENT_CSUM EXTENT_CSUM 8798638964736) itemoff 1751 itemsize 2244
range start 8798638964736 end 8798641262592 length 2297856
When reading the above tree block, we have extent_buffer->refs = 2 in
the context:
- initial one from __alloc_extent_buffer()
alloc_extent_buffer()
|- __alloc_extent_buffer()
|- atomic_set(&eb->refs, 1)
- one being added to fs_info->buffer_radix
alloc_extent_buffer()
|- check_buffer_tree_ref()
|- atomic_inc(&eb->refs)
So if even we call free_extent_buffer() in read_tree_block or other
similar situation, we only decrease the refs by 1, it doesn't reach 0
and won't be freed right now.
The staled eb and its corrupted content will still be kept cached.
Furthermore, we have several extra cases where we either don't do first
key check or the check is not proper for all callers:
- scrub
We just don't have first key in this context.
- shared tree block
One tree block can be shared by several snapshot/subvolume trees.
In that case, the first key check for one subvolume doesn't apply to
another.
So for the above reasons, a corrupted extent buffer can sneak into the
buffer cache.
[FIX]
Call verify_level_key in read_block_for_search to do another
verification. For that purpose the function is exported.
Due to above reasons, although we can free corrupted extent buffer from
cache, we still need the check in read_block_for_search(), for scrub and
shared tree blocks.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202755
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202757
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202759
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202761
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202767
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202769
Reported-by: Yoon Jungyeon <jungyeon@gatech.edu>
CC: stable@vger.kernel.org # 4.19+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If a an eb fails to be read for whatever reason - it's corrupted on disk
and parent transid/key validations fail or IO for eb pages fail then
this buffer must be removed from the buffer cache. Currently the code
calls free_extent_buffer if an error occurs. Unfortunately this doesn't
achieve the desired behavior since btrfs_find_create_tree_block returns
with eb->refs == 2.
On the other hand free_extent_buffer will only decrement the refs once
leaving it added to the buffer cache radix tree. This enables later
code to look up the buffer from the cache and utilize it potentially
leading to a crash.
The correct way to free the buffer is call free_extent_buffer_stale.
This function will correctly call atomic_dec explicitly for the buffer
and subsequently call release_extent_buffer which will decrement the
final reference thus correctly remove the invalid buffer from buffer
cache. This change affects only newly allocated buffers since they have
eb->refs == 2.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202755
Reported-by: Jungyeon <jungyeon@gatech.edu>
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
From the introduction of btrfs_(set|clear)_header_flag, there is no
usage of its return value. So just make it return void.
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>
Commit d2311e6985 ("btrfs: relocation: Delay reloc tree deletion after
merge_reloc_roots()") expands the life span of root->reloc_root.
This breaks certain checs of fs_info->reloc_ctl. Before that commit, if
we have a root with valid reloc_root, then it's ensured to have
fs_info->reloc_ctl.
But now since reloc_root doesn't always mean a valid fs_info->reloc_ctl,
such check is unreliable and can cause the following NULL pointer
dereference:
BUG: unable to handle kernel NULL pointer dereference at 00000000000005c1
IP: btrfs_reloc_pre_snapshot+0x20/0x50 [btrfs]
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 0 PID: 10379 Comm: snapperd Not tainted
Call Trace:
create_pending_snapshot+0xd7/0xfc0 [btrfs]
create_pending_snapshots+0x8e/0xb0 [btrfs]
btrfs_commit_transaction+0x2ac/0x8f0 [btrfs]
btrfs_mksubvol+0x561/0x570 [btrfs]
btrfs_ioctl_snap_create_transid+0x189/0x190 [btrfs]
btrfs_ioctl_snap_create_v2+0x102/0x150 [btrfs]
btrfs_ioctl+0x5c9/0x1e60 [btrfs]
do_vfs_ioctl+0x90/0x5f0
SyS_ioctl+0x74/0x80
do_syscall_64+0x7b/0x150
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x7fd7cdab8467
Fix it by explicitly checking fs_info->reloc_ctl other than using the
implied root->reloc_root.
Fixes: d2311e6985 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots")
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In case we hit the error case for a metadata buffer in
end_bio_extent_readpage then 'ret' won't really be checked before it's
written again to. This means the -EIO in this case will never be
checked, just remove it.
Fixes-coverity-id: 1442513
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently extent_readpages (called from btrfs_readpages) will always
call __extent_readpages which tries to create contiguous range of pages
and call __do_contiguous_readpages when such contiguous range is
created.
It turns out this is unnecessary due to the fact that generic MM code
always calls filesystem's ->readpages callback (btrfs_readpages in
this case) with already contiguous pages. Armed with this knowledge it's
possible to simplify extent_readpages by eliminating the call to
__extent_readpages and directly calling contiguous_readpages.
The only edge case that needs to be handled is when
add_to_page_cache_lru fails. This is easy as all that is needed is to
submit whatever is the number of pages successfully added to the lru.
This can happen when the page is already in the range, so it does not
need to be read again, and we can't do anything else in case of other
errors.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The member is tracking simple status of the lock, we can use bool for
that and make some room for further space reduction in the structure.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Use the helpers where open coded. On non-debug builds, the warnings will
not trigger and extent_buffer::write_locks become unused and can be
moved to the appropriate section, saving a few bytes.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
The write_locks are a simple counter to track locking balance and used
to assert tree locks. Add helpers to make it conditionally work only in
DEBUG builds. Will be used in followup patches.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Use the helpers where open coded. On non-debug builds, the warnings will
not trigger and extent_buffer::read_locks become unused and can be
moved to the appropriate section, saving a few bytes.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
The read_locks are a simple counter to track locking balance and used to
assert tree locks. Add helpers to make it conditionally work only in
DEBUG builds. Will be used in followup patches.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Use the helpers where open coded. On non-debug builds, the warnings will
not trigger and extent_buffer::spining_readers become unused and can be
moved to the appropriate section, saving a few bytes.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Add helpers for conditional DEBUG build to assert that the extent buffer
spinning_readers constraints are met. Will be used in followup patches.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Use the helpers where open coded. On non-debug builds, the warnings will
not trigger and extent_buffer::spining_writers become unused and can be
moved to the appropriate section, saving a few bytes.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Add helpers for conditional DEBUG build to assert that the extent buffer
spinning_writers constraints are met. Will be used in followup patches.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
This flag just became synonymous to EXTENT_LOCKED, so just remove it and
used EXTENT_LOCKED directly. 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>
This flag was introduced in a52d9a8033 ("Btrfs: Extent based page
cache code.") and subsequently it's usage effectively was removed by
1edbb734b4 ("Btrfs: reduce CPU usage in the extent_state tree") and
f2a97a9dbd ("btrfs: remove all unused functions"). Just remove it,
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>
When building with -Wsometimes-uninitialized, Clang warns:
fs/btrfs/uuid-tree.c:129:13: warning: variable 'eb' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
fs/btrfs/uuid-tree.c:129:13: warning: variable 'offset' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
Clang can't tell that all cases are covered with this final else if.
Just turn it into an else so that it is clear.
Link: https://github.com/ClangBuiltLinux/linux/issues/385
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_set_prop() takes transaction pointer as the first argument,
however in ioctl.c for the purpose of setting the compression property,
we call btrfs_set_prop() with NULL transaction pointer. Down in
the call chain btrfs_setxattr() starts transaction to update the
attribute and also to update the inode.
So for clarity, create btrfs_set_prop_trans() with no transaction
pointer as argument, in preparation to start transaction here instead of
doing it down the call chain at btrfs_setxattr().
Also now the btrfs_set_prop() is a static function.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
fs_info is commonly used to represent struct fs_info *, rename
to fs_private to avoid confusion.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Drop forward declaration of the functions:
- prop_compression_validate
- prop_compression_apply
- prop_compression_extract
No functional changes.
Reviewed-by: Nikolay Borisov <nborisov@suse.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>
btrfs_set_prop() is a redirect to __btrfs_set_prop() with the
transaction handle equal to NULL. __btrfs_set_prop() in turn passes
this to do_setxattr() which then transaction is actually created.
Instead merge __btrfs_set_prop() to btrfs_set_prop(), and update the
caller with NULL argument.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Since commit c40a3d38af ("Btrfs: Compute and look up csums based on
sectorsized blocks") we do a kmap_atomic() on the contents of a bvec.
The code before c40a3d38af had the kmap region just around the
checksumming too.
kmap_atomic() in turn does a preempt_disable() and pagefault_disable(),
so we shouldn't map the data for too long. Reduce the time the bvec's
page is mapped to when we actually need it.
Performance wise it doesn't seem to make a huge difference with a 2 vcpu VM
on a /dev/zram device:
vanilla patched delta
write 17.4MiB/s 17.8MiB/s +0.4MiB/s (+2%)
read 40.6MiB/s 41.5MiB/s +0.9MiB/s (+2%)
The following fio job profile was used in the comparision:
[global]
ioengine=libaio
direct=1
sync=1
norandommap
time_based
runtime=10m
size=100m
group_reporting
numjobs=2
[test]
filename=/mnt/test/fio
rw=randrw
rwmixread=70
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
