The readdir implementation currently processes always up to the last index
it finds. This however can result in an infinite loop if the directory has
a large number of entries such that they won't all fit in the given buffer
passed to the readdir callback, that is, dir_emit() returns a non-zero
value. Because in that case readdir() will be called again and if in the
meanwhile new directory entries were added and we still can't put all the
remaining entries in the buffer, we keep repeating this over and over.
The following C program and test script reproduce the problem:
$ cat /mnt/readdir_prog.c
#include <sys/types.h>
#include <dirent.h>
#include <stdio.h>
int main(int argc, char *argv[])
{
DIR *dir = opendir(".");
struct dirent *dd;
while ((dd = readdir(dir))) {
printf("%s\n", dd->d_name);
rename(dd->d_name, "TEMPFILE");
rename("TEMPFILE", dd->d_name);
}
closedir(dir);
}
$ gcc -o /mnt/readdir_prog /mnt/readdir_prog.c
$ cat test.sh
#!/bin/bash
DEV=/dev/sdi
MNT=/mnt/sdi
mkfs.btrfs -f $DEV &> /dev/null
#mkfs.xfs -f $DEV &> /dev/null
#mkfs.ext4 -F $DEV &> /dev/null
mount $DEV $MNT
mkdir $MNT/testdir
for ((i = 1; i <= 2000; i++)); do
echo -n > $MNT/testdir/file_$i
done
cd $MNT/testdir
/mnt/readdir_prog
cd /mnt
umount $MNT
This behaviour is surprising to applications and it's unlike ext4, xfs,
tmpfs, vfat and other filesystems, which always finish. In this case where
new entries were added due to renames, some file names may be reported
more than once, but this varies according to each filesystem - for example
ext4 never reported the same file more than once while xfs reports the
first 13 file names twice.
So change our readdir implementation to track the last index number when
opendir() is called and then make readdir() never process beyond that
index number. This gives the same behaviour as ext4.
Reported-by: Rob Landley <rob@landley.net>
Link: https://lore.kernel.org/linux-btrfs/2c8c55ec-04c6-e0dc-9c5c-8c7924778c35@landley.net/
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217681
CC: stable@vger.kernel.org # 6.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For directories with encrypted files/filenames, we need to store a flag
indicating this fact. There's no room in other fields, so we'll need to
borrow a bit from dir_type. Since it's now a combination of type and
flags, we rename it to dir_flags to reflect its new usage.
The new flag, FT_ENCRYPTED, indicates a directory containing encrypted
data, which is orthogonal to file type; therefore, add the new
flag, and make conversion from directory type to file type strip the
flag.
As the file types almost never change we can afford to use the bits.
Actual usage will be guarded behind an incompat bit, this patch only
adds the support for later use by fscrypt.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When logging a directory we start by flushing all its delayed items.
That results in adding dir index items to the subvolume btree, for new
dentries, and removing dir index items from the subvolume btree for any
dentries that were deleted.
This makes it straightforward to log a directory simply by iterating over
all the modified subvolume btree leaves, especially when we used to log
both dir index keys and dir item keys (before commit 339d035424
("btrfs: only copy dir index keys when logging a directory") and when we
used to copy old dir index entries for leaves modified in the current
transaction (before commit 732d591a5d ("btrfs: stop copying old dir
items when logging a directory")).
From an efficiency point of view this has a couple of drawbacks:
1) Adds extra latency, due to copying delayed items to the subvolume btree
and deleting dir index items from the btree.
Further if there are other tasks accessing the btree, which is common
(syscalls like creat, mkdir, rename, link, unlink, truncate, reflinks,
etc, finishing an ordered extent, etc), lock contention can cause
further delays, both to the task logging a directory and to the other
tasks accessing the btree;
2) More time spent overall flushing delayed items, if after logging the
directory further changes are done to the directory in the same
transaction.
For example, if we add 10 dentries to a directory, fsync it, add more
10 dentries, fsync it again, then add more 10 dentries and fsync it
again, then we end up inserting 3 batches of 10 items to the subvolume
btree. With the changes from this patch, we flush all the delayed items
to the btree only once - a single batch of 30 items, and outside the
logging code (transaction commit or when delayed items are flushed
asynchronously).
This change simply skips the flushing of delayed items every time we log a
directory. Instead we copy the delayed insertion items directly to the log
tree and delete delayed deletion items directly from the log tree.
Therefore avoiding changing first the subvolume btree and then scanning it
for new items to copy from it to the log tree and detecting deletions
by observing gaps in consecutive dir index keys in subvolume btree leaves.
Running the following tests on a non-debug kernel (Debian's default kernel
config), on a box with a NVMe device, a 12 cores Intel CPU and 64G of ram,
produced the results below.
The results compare a branch without this patch and all the other patches
it depends on versus the same branch with the patchset applied.
The patchset is comprised of the following patches:
btrfs: don't drop dir index range items when logging a directory
btrfs: remove the root argument from log_new_dir_dentries()
btrfs: update stale comment for log_new_dir_dentries()
btrfs: free list element sooner at log_new_dir_dentries()
btrfs: avoid memory allocation at log_new_dir_dentries() for common case
btrfs: remove root argument from btrfs_delayed_item_reserve_metadata()
btrfs: store index number instead of key in struct btrfs_delayed_item
btrfs: remove unused logic when looking up delayed items
btrfs: shrink the size of struct btrfs_delayed_item
btrfs: search for last logged dir index if it's not cached in the inode
btrfs: move need_log_inode() to above log_conflicting_inodes()
btrfs: move log_new_dir_dentries() above btrfs_log_inode()
btrfs: log conflicting inodes without holding log mutex of the initial inode
btrfs: skip logging parent dir when conflicting inode is not a dir
btrfs: use delayed items when logging a directory
Custom test script for testing time spent at btrfs_log_inode():
#!/bin/bash
DEV=/dev/nvme0n1
MNT=/mnt/nvme0n1
# Total number of files to create in the test directory.
NUM_FILES=10000
# Fsync after creating or renaming N files.
FSYNC_AFTER=100
umount $DEV &> /dev/null
mkfs.btrfs -f $DEV
mount -o ssd $DEV $MNT
TEST_DIR=$MNT/testdir
mkdir $TEST_DIR
echo "Creating files..."
for ((i = 1; i <= $NUM_FILES; i++)); do
echo -n > $TEST_DIR/file_$i
if (( ($i % $FSYNC_AFTER) == 0 )); then
xfs_io -c "fsync" $TEST_DIR
fi
done
sync
echo "Renaming files..."
for ((i = 1; i <= $NUM_FILES; i++)); do
mv $TEST_DIR/file_$i $TEST_DIR/file_$i.renamed
if (( ($i % $FSYNC_AFTER) == 0 )); then
xfs_io -c "fsync" $TEST_DIR
fi
done
umount $MNT
And using the following bpftrace script to capture the total time that is
spent at btrfs_log_inode():
#!/usr/bin/bpftrace
k:btrfs_log_inode
{
@start_log_inode[tid] = nsecs;
}
kr:btrfs_log_inode
/@start_log_inode[tid]/
{
$dur = (nsecs - @start_log_inode[tid]) / 1000;
@btrfs_log_inode_total_time = sum($dur);
delete(@start_log_inode[tid]);
}
END
{
clear(@start_log_inode);
}
Result before applying patchset:
@btrfs_log_inode_total_time: 622642
Result after applying patchset:
@btrfs_log_inode_total_time: 354134 (-43.1% time spent)
The following dbench script was also used for testing:
#!/bin/bash
NUM_JOBS=$(nproc --all)
DEV=/dev/nvme0n1
MNT=/mnt/nvme0n1
MOUNT_OPTIONS="-o ssd"
MKFS_OPTIONS="-O no-holes -R free-space-tree"
echo "performance" | \
tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
umount $DEV &> /dev/null
mkfs.btrfs -f $MKFS_OPTIONS $DEV
mount $MOUNT_OPTIONS $DEV $MNT
dbench -D $MNT --skip-cleanup -t 120 -S $NUM_JOBS
umount $MNT
Before patchset:
Operation Count AvgLat MaxLat
----------------------------------------
NTCreateX 3322265 0.034 21.032
Close 2440562 0.002 0.994
Rename 140664 1.150 269.633
Unlink 670796 1.093 269.678
Deltree 96 5.481 15.510
Mkdir 48 0.004 0.052
Qpathinfo 3010924 0.014 8.127
Qfileinfo 528055 0.001 0.518
Qfsinfo 552113 0.003 0.372
Sfileinfo 270575 0.005 0.688
Find 1164176 0.052 13.931
WriteX 1658537 0.019 5.918
ReadX 5207412 0.003 1.034
LockX 10818 0.003 0.079
UnlockX 10818 0.002 0.313
Flush 232811 1.027 269.735
Throughput 869.867 MB/sec (sync dirs) 12 clients 12 procs max_latency=269.741 ms
After patchset:
Operation Count AvgLat MaxLat
----------------------------------------
NTCreateX 4152738 0.029 20.863
Close 3050770 0.002 1.119
Rename 175829 0.871 211.741
Unlink 838447 0.845 211.724
Deltree 120 4.798 14.162
Mkdir 60 0.003 0.005
Qpathinfo 3763807 0.011 4.673
Qfileinfo 660111 0.001 0.400
Qfsinfo 690141 0.003 0.429
Sfileinfo 338260 0.005 0.725
Find 1455273 0.046 6.787
WriteX 2073307 0.017 5.690
ReadX 6509193 0.003 1.171
LockX 13522 0.003 0.077
UnlockX 13522 0.002 0.125
Flush 291044 0.811 211.631
Throughput 1089.27 MB/sec (sync dirs) 12 clients 12 procs max_latency=211.750 ms
(+25.2% throughput, -21.5% max latency)
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently struct btrfs_delayed_item has a base size of 96 bytes, but its
size can be decreased by doing the following 2 tweaks:
1) Change data_len from u32 to u16. Our maximum possible leaf size is 64K,
so the data_len can never be larger than that, and in fact it is always
much smaller than that. The max length for a dentry's name is ensured
at the VFS level (PATH_MAX, 4096 bytes) and in struct btrfs_inode_ref
and btrfs_dir_item we use a u16 to store the name's length;
2) Change 'ins_or_del' to a 1 bit enum, which is all we need since it
can only have 2 values. After this there's also no longer the need to
BUG_ON() before using 'ins_or_del' in several places. Also rename the
field from 'ins_or_del' to 'type', which is more clear.
These two tweaks decrease the size of struct btrfs_delayed_item from 96
bytes down to 88 bytes. A previous patch already reduced the size of this
structure by 16 bytes, but an upcoming change will increase its size by
16 bytes (adding a struct list_head element).
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
All delayed items are for dir index keys, so there's really no point of
having an embedded struct btrfs_key in struct btrfs_delayed_item, which
makes the structure use more space than necessary (and adds a hole of 7
bytes).
So replace the key field with an index number (u64), which reduces the
size of struct btrfs_delayed_item from 112 bytes down to 96 bytes.
Some upcoming work will increase the structure size by 16 bytes, so this
change compensates for that future size increase.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Whenever we want to create a new dir index item (when creating an inode,
create a hard link, rename a file) we reserve 1 unit of metadata space
for it in a transaction (that's 256K for a node/leaf size of 16K), and
then create a delayed insertion item for it to be added later to the
subvolume's tree. That unit of metadata is kept until the delayed item
is inserted into the subvolume tree, which may take a while to happen
(in the worst case, it's done only when the transaction commits). If we
have multiple dir index items to insert for the same directory, say N
index items, and they all fit in a single leaf of metadata, then we are
holding N units of reserved metadata space when all we need is 1 unit.
This change addresses that, whenever a new delayed dir index item is
added, we release the unit of metadata the caller has reserved when it
started the transaction if adding that new dir index item does not
result in touching one more metadata leaf, otherwise the reservation
is kept by transferring it from the transaction block reserve to the
delayed items block reserve, just like before. Given that with a leaf
size of 16K we can have a few hundred dir index items in a single leaf
(the exact value depends on file name lengths), this reduces pressure on
metadata reservation by releasing unnecessary space much sooner.
The following fs_mark test showed some improvement when creating many
files in parallel on machine running a non debug kernel (debian's default
kernel config) with 12 cores:
$ cat test.sh
#!/bin/bash
DEV=/dev/nvme0n1
MNT=/mnt/nvme0n1
MOUNT_OPTIONS="-o ssd"
FILES=100000
THREADS=$(nproc --all)
echo "performance" | \
tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
mkfs.btrfs -f $DEV
mount $MOUNT_OPTIONS $DEV $MNT
OPTS="-S 0 -L 10 -n $FILES -s 0 -t $THREADS -k"
for ((i = 1; i <= $THREADS; i++)); do
OPTS="$OPTS -d $MNT/d$i"
done
fs_mark $OPTS
umount $MNT
Before:
FSUse% Count Size Files/sec App Overhead
2 1200000 0 225991.3 5465891
4 2400000 0 345728.1 5512106
4 3600000 0 346959.5 5557653
8 4800000 0 329643.0 5587548
8 6000000 0 312657.4 5606717
8 7200000 0 281707.5 5727985
12 8400000 0 88309.8 5020422
12 9600000 0 85835.9 5207496
16 10800000 0 81039.2 5404964
16 12000000 0 58548.6 5842468
After:
FSUse% Count Size Files/sec App Overhead
2 1200000 0 230604.5 5778375
4 2400000 0 348908.3 5508072
4 3600000 0 357028.7 5484337
6 4800000 0 342898.3 5565703
6 6000000 0 314670.8 5751555
8 7200000 0 282548.2 5778177
12 8400000 0 90844.9 5306819
12 9600000 0 86963.1 5304689
16 10800000 0 89113.2 5455248
16 12000000 0 86693.5 5518933
The "after" results are after applying this patch and all the other
patches in the same patchset, which is comprised of the following
changes:
btrfs: balance btree dirty pages and delayed items after a rename
btrfs: free the path earlier when creating a new inode
btrfs: balance btree dirty pages and delayed items after clone and dedupe
btrfs: add assertions when deleting batches of delayed items
btrfs: deal with deletion errors when deleting delayed items
btrfs: refactor the delayed item deletion entry point
btrfs: improve batch deletion of delayed dir index items
btrfs: assert that delayed item is a dir index item when adding it
btrfs: improve batch insertion of delayed dir index items
btrfs: do not BUG_ON() on failure to reserve metadata for delayed item
btrfs: set delayed item type when initializing it
btrfs: reduce amount of reserved metadata for delayed item insertion
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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 current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array
member[1][2], introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning in
case the flexible array does not occur last in the structure, which will
help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by this
change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero." [1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
rb_first_cached() trades an extra pointer "leftmost" for doing the same job as
rb_first() but in O(1).
Functions manipulating delayed_item need to get the first entry, this converts
it to use rb_first_cached().
For more details about the optimization see patch "Btrfs: delayed-refs:
use rb_first_cached for href_root".
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
It can be referenced from the passed transaction handle.
Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
It can be referenced from the passed transaction handle.
Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Remove GPL boilerplate text (long, short, one-line) and keep the rest,
ie. personal, company or original source copyright statements. Add the
SPDX header.
Unify the include protection macros to match the file names.
Signed-off-by: David Sterba <dsterba@suse.com>
The __cold functions are placed to a special section, as they're
expected to be called rarely. This could help i-cache prefetches or help
compiler to decide which branches are more/less likely to be taken
without any other annotations needed.
Though we can't add more __exit annotations, it's still possible to add
__cold (that's also added with __exit). That way the following function
categories are tagged:
- printf wrappers, error messages
- exit helpers
Signed-off-by: David Sterba <dsterba@suse.com>
We already pass the transaction which has a reference to the fs_info,
so use that. No functional changes.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There are loads of functions in btrfs that accept a root parameter
but only use it to obtain an fs_info pointer. Let's convert those to
just accept an fs_info pointer directly.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This results in btrfs_assert_delayed_root_empty and
btrfs_destroy_delayed_inode taking an fs_info instead of a root.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If we process the last item in the leaf and hit an I/O error while
reading the next leaf, we return -EIO without having adjusted the
position. Since we have emitted dirents, getdents() will return
the byte count to the user instead of the error. Subsequent callers
will emit the last successful dirent again, and return -EIO again,
with the same result. Callers loop forever.
Instead, if we always increment ctx->pos after emitting or skipping
the dirent, we'll be sure that we won't hit the same one again. When
we go to process the next leaf, we won't have emitted any dirents
and the -EIO will be returned to the user properly. We also don't
need to track if we've emitted a dirent already or if we've changed
the position yet.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Commit fe742fd4f9 ("Revert "btrfs: switch to ->iterate_shared()"")
backed out the conversion to ->iterate_shared() for Btrfs because the
delayed inode handling in btrfs_real_readdir() is racy. However, we can
still do readdir in parallel if there are no delayed nodes.
This is a temporary fix which upgrades the shared inode lock to an
exclusive lock only when we have delayed items until we come up with a
more complete solution. While we're here, rename the
btrfs_{get,put}_delayed_items functions to make it very clear that
they're just for readdir.
Tested with xfstests and by doing a parallel kernel build:
while make tinyconfig && make -j4 && git clean dqfx; do
:
done
along with a bunch of parallel finds in another shell:
while true; do
for ((i=0; i<4; i++)); do
find . >/dev/null &
done
wait
done
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
The value of ctx->pos in the last readdir call is supposed to be set to
INT_MAX due to 32bit compatibility, unless 'pos' is intentially set to a
larger value, then it's LLONG_MAX.
There's a report from PaX SIZE_OVERFLOW plugin that "ctx->pos++"
overflows (https://forums.grsecurity.net/viewtopic.php?f=1&t=4284), on a
64bit arch, where the value is 0x7fffffffffffffff ie. LLONG_MAX before
the increment.
We can get to that situation like that:
* emit all regular readdir entries
* still in the same call to readdir, bump the last pos to INT_MAX
* next call to readdir will not emit any entries, but will reach the
bump code again, finds pos to be INT_MAX and sets it to LLONG_MAX
Normally this is not a problem, but if we call readdir again, we'll find
'pos' set to LLONG_MAX and the unconditional increment will overflow.
The report from Victor at
(http://thread.gmane.org/gmane.comp.file-systems.btrfs/49500) with debugging
print shows that pattern:
Overflow: e
Overflow: 7fffffff
Overflow: 7fffffffffffffff
PAX: size overflow detected in function btrfs_real_readdir
fs/btrfs/inode.c:5760 cicus.935_282 max, count: 9, decl: pos; num: 0;
context: dir_context;
CPU: 0 PID: 2630 Comm: polkitd Not tainted 4.2.3-grsec #1
Hardware name: Gigabyte Technology Co., Ltd. H81ND2H/H81ND2H, BIOS F3 08/11/2015
ffffffff81901608 0000000000000000 ffffffff819015e6 ffffc90004973d48
ffffffff81742f0f 0000000000000007 ffffffff81901608 ffffc90004973d78
ffffffff811cb706 0000000000000000 ffff8800d47359e0 ffffc90004973ed8
Call Trace:
[<ffffffff81742f0f>] dump_stack+0x4c/0x7f
[<ffffffff811cb706>] report_size_overflow+0x36/0x40
[<ffffffff812ef0bc>] btrfs_real_readdir+0x69c/0x6d0
[<ffffffff811dafc8>] iterate_dir+0xa8/0x150
[<ffffffff811e6d8d>] ? __fget_light+0x2d/0x70
[<ffffffff811dba3a>] SyS_getdents+0xba/0x1c0
Overflow: 1a
[<ffffffff811db070>] ? iterate_dir+0x150/0x150
[<ffffffff81749b69>] entry_SYSCALL_64_fastpath+0x12/0x83
The jump from 7fffffff to 7fffffffffffffff happens when new dir entries
are not yet synced and are processed from the delayed list. Then the code
could go to the bump section again even though it might not emit any new
dir entries from the delayed list.
The fix avoids entering the "bump" section again once we've finished
emitting the entries, both for synced and delayed entries.
References: https://forums.grsecurity.net/viewtopic.php?f=1&t=4284
Reported-by: Victor <services@swwu.com>
CC: stable@vger.kernel.org
Signed-off-by: David Sterba <dsterba@suse.com>
Tested-by: Holger Hoffstätte <holger.hoffstaette@googlemail.com>
Signed-off-by: Chris Mason <clm@fb.com>
The inode reference item is close to inode item, so we insert it simultaneously
with the inode item insertion when we create a file/directory.. In fact, we also
can handle the inode reference deletion by the same way. So we made this patch to
introduce the delayed inode reference deletion for the single link inode(At most
case, the file doesn't has hard link, so we don't take the hard link into account).
This function is based on the delayed inode mechanism. After applying this patch,
we can reduce the time of the file/directory deletion by ~10%.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
The delayed inode code batches up changes to the btree in hopes of doing
them in bulk. As the changes build up, processes kick off worker
threads and wait for them to make progress.
The current code kicks off an async work queue item for each delayed
node, which creates a lot of churn. It also uses a fixed 1 HZ waiting
period for the throttle, which allows us to build a lot of pending
work and can slow down the commit.
This changes us to watch a sequence counter as it is bumped during the
operations. We kick off fewer work items and have each work item do
more work.
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
We're running into having 50-100 orphans left over with xfstests 83
because of ENOSPC when trying to start the transaction for the inode update.
But in fact, it makes no sense in updating the inode for the new size while
we're deleting the stupid thing. This patch fixes this problem.
Reported-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Those crazy gentoo guys have been complaining about ENOSPC errors on their
portage volumes. This is because doing things like untar tends to create
lots of new files which will soak up all the reservation space in the
delayed inodes. Usually this gets papered over by the fact that we will try
and commit the transaction, however if this happens in the wrong spot or we
choose not to commit the transaction you will be screwed. So add the
ability to expclitly flush delayed inodes to free up space. Please test
this out guys to make sure it works since as usual I cannot reproduce.
Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
the items of the delayed inodes were forgotten to be freed, this patch
fixes it.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
This allows us to move duplicated code in <asm/atomic.h>
(atomic_inc_not_zero() for now) to <linux/atomic.h>
Signed-off-by: Arun Sharma <asharma@fb.com>
Reviewed-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Miller <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When iputting the inode, We may leave the delayed nodes if they have some
delayed items that have not been dealt with. So when the inode is read again,
we must look up the relative delayed node, and use the information in it to
initialize the inode. Or we will get inconsonant inode information, it may
cause that the same directory index number is allocated again, and hit the
following oops:
[ 5447.554187] err add delayed dir index item(name: pglog_0.965_0) into the
insertion tree of the delayed node(root id: 262, inode id: 258, errno: -17)
[ 5447.569766] ------------[ cut here ]------------
[ 5447.575361] kernel BUG at fs/btrfs/delayed-inode.c:1301!
[SNIP]
[ 5447.790721] Call Trace:
[ 5447.793191] [<ffffffffa0641c4e>] btrfs_insert_dir_item+0x189/0x1bb [btrfs]
[ 5447.800156] [<ffffffffa0651a45>] btrfs_add_link+0x12b/0x191 [btrfs]
[ 5447.806517] [<ffffffffa0651adc>] btrfs_add_nondir+0x31/0x58 [btrfs]
[ 5447.812876] [<ffffffffa0651d6a>] btrfs_create+0xf9/0x197 [btrfs]
[ 5447.818961] [<ffffffff8111f840>] vfs_create+0x72/0x92
[ 5447.824090] [<ffffffff8111fa8c>] do_last+0x22c/0x40b
[ 5447.829133] [<ffffffff8112076a>] path_openat+0xc0/0x2ef
[ 5447.834438] [<ffffffff810c58e2>] ? __perf_event_task_sched_out+0x24/0x44
[ 5447.841216] [<ffffffff8103ecdd>] ? perf_event_task_sched_out+0x59/0x67
[ 5447.847846] [<ffffffff81121a79>] do_filp_open+0x3d/0x87
[ 5447.853156] [<ffffffff811e126c>] ? strncpy_from_user+0x43/0x4d
[ 5447.859072] [<ffffffff8111f1f5>] ? getname_flags+0x2e/0x80
[ 5447.864636] [<ffffffff8111f179>] ? do_getname+0x14b/0x173
[ 5447.870112] [<ffffffff8111f1b7>] ? audit_getname+0x16/0x26
[ 5447.875682] [<ffffffff8112b1ab>] ? spin_lock+0xe/0x10
[ 5447.880882] [<ffffffff81112d39>] do_sys_open+0x69/0xae
[ 5447.886153] [<ffffffff81112db1>] sys_open+0x20/0x22
[ 5447.891114] [<ffffffff813b9aab>] system_call_fastpath+0x16/0x1b
Fix it by reusing the old delayed node.
Reported-by: Jim Schutt <jaschut@sandia.gov>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Tested-by: Jim Schutt <jaschut@sandia.gov>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Snapshot creation has two phases. One is the initial snapshot setup,
and the second is done during commit, while nobody is allowed to modify
the root we are snapshotting.
The delayed metadata insertion code can break that rule, it does a
delayed inode update on the inode of the parent of the snapshot,
and delayed directory item insertion.
This makes sure to run the pending delayed operations before we
record the snapshot root, which avoids corruptions.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Changelog V5 -> V6:
- Fix oom when the memory load is high, by storing the delayed nodes into the
root's radix tree, and letting btrfs inodes go.
Changelog V4 -> V5:
- Fix the race on adding the delayed node to the inode, which is spotted by
Chris Mason.
- Merge Chris Mason's incremental patch into this patch.
- Fix deadlock between readdir() and memory fault, which is reported by
Itaru Kitayama.
Changelog V3 -> V4:
- Fix nested lock, which is reported by Itaru Kitayama, by updating space cache
inode in time.
Changelog V2 -> V3:
- Fix the race between the delayed worker and the task which does delayed items
balance, which is reported by Tsutomu Itoh.
- Modify the patch address David Sterba's comment.
- Fix the bug of the cpu recursion spinlock, reported by Chris Mason
Changelog V1 -> V2:
- break up the global rb-tree, use a list to manage the delayed nodes,
which is created for every directory and file, and used to manage the
delayed directory name index items and the delayed inode item.
- introduce a worker to deal with the delayed nodes.
Compare with Ext3/4, the performance of file creation and deletion on btrfs
is very poor. the reason is that btrfs must do a lot of b+ tree insertions,
such as inode item, directory name item, directory name index and so on.
If we can do some delayed b+ tree insertion or deletion, we can improve the
performance, so we made this patch which implemented delayed directory name
index insertion/deletion and delayed inode update.
Implementation:
- introduce a delayed root object into the filesystem, that use two lists to
manage the delayed nodes which are created for every file/directory.
One is used to manage all the delayed nodes that have delayed items. And the
other is used to manage the delayed nodes which is waiting to be dealt with
by the work thread.
- Every delayed node has two rb-tree, one is used to manage the directory name
index which is going to be inserted into b+ tree, and the other is used to
manage the directory name index which is going to be deleted from b+ tree.
- introduce a worker to deal with the delayed operation. This worker is used
to deal with the works of the delayed directory name index items insertion
and deletion and the delayed inode update.
When the delayed items is beyond the lower limit, we create works for some
delayed nodes and insert them into the work queue of the worker, and then
go back.
When the delayed items is beyond the upper bound, we create works for all
the delayed nodes that haven't been dealt with, and insert them into the work
queue of the worker, and then wait for that the untreated items is below some
threshold value.
- When we want to insert a directory name index into b+ tree, we just add the
information into the delayed inserting rb-tree.
And then we check the number of the delayed items and do delayed items
balance. (The balance policy is above.)
- When we want to delete a directory name index from the b+ tree, we search it
in the inserting rb-tree at first. If we look it up, just drop it. If not,
add the key of it into the delayed deleting rb-tree.
Similar to the delayed inserting rb-tree, we also check the number of the
delayed items and do delayed items balance.
(The same to inserting manipulation)
- When we want to update the metadata of some inode, we cached the data of the
inode into the delayed node. the worker will flush it into the b+ tree after
dealing with the delayed insertion and deletion.
- We will move the delayed node to the tail of the list after we access the
delayed node, By this way, we can cache more delayed items and merge more
inode updates.
- If we want to commit transaction, we will deal with all the delayed node.
- the delayed node will be freed when we free the btrfs inode.
- Before we log the inode items, we commit all the directory name index items
and the delayed inode update.
I did a quick test by the benchmark tool[1] and found we can improve the
performance of file creation by ~15%, and file deletion by ~20%.
Before applying this patch:
Create files:
Total files: 50000
Total time: 1.096108
Average time: 0.000022
Delete files:
Total files: 50000
Total time: 1.510403
Average time: 0.000030
After applying this patch:
Create files:
Total files: 50000
Total time: 0.932899
Average time: 0.000019
Delete files:
Total files: 50000
Total time: 1.215732
Average time: 0.000024
[1] http://marc.info/?l=linux-btrfs&m=128212635122920&q=p3
Many thanks for Kitayama-san's help!
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: David Sterba <dave@jikos.cz>
Tested-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Tested-by: Itaru Kitayama <kitayama@cl.bb4u.ne.jp>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
