btrfs: do not pin logs too early during renames

During renames we pin the logs of the roots a bit too early, before the calls to btrfs_insert_inode_ref(). We can pin the logs after those calls, since those will not change anything in a log tree. In a scenario where we have multiple and diverse filesystem operations running in parallel, those calls can take a significant amount of time, due to lock contention on extent buffers, and delay log commits from other tasks for longer than necessary. So just pin logs after calls to btrfs_insert_inode_ref() and right before the first operation that can update a log tree. The following script that uses dbench was used for testing: $ cat dbench-test.sh #!/bin/bash DEV=/dev/nvme0n1 MNT=/mnt/nvme0n1 MOUNT_OPTIONS="-o ssd" MKFS_OPTIONS="-m single -d single" 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 -t 120 16 umount $MNT The tests were run on a machine with 12 cores, 64G of RAN, a NVMe device and using a non-debug kernel config (Debian's default config). The results compare a branch without this patch and without the previous patch in the series, that has the subject: "btrfs: eliminate some false positives when checking if inode was logged" Versus the same branch with these two patches applied. dbench with 8 clients, results before: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 4391359 0.009 249.745 Close 3225882 0.001 3.243 Rename 185953 0.065 240.643 Unlink 886669 0.049 249.906 Deltree 112 2.455 217.433 Mkdir 56 0.002 0.004 Qpathinfo 3980281 0.004 3.109 Qfileinfo 697579 0.001 0.187 Qfsinfo 729780 0.002 2.424 Sfileinfo 357764 0.004 1.415 Find 1538861 0.016 4.863 WriteX 2189666 0.010 3.327 ReadX 6883443 0.002 0.729 LockX 14298 0.002 0.073 UnlockX 14298 0.001 0.042 Flush 307777 2.447 303.663 Throughput 1149.6 MB/sec 8 clients 8 procs max_latency=303.666 ms dbench with 8 clients, results after: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 4269920 0.009 213.532 Close 3136653 0.001 0.690 Rename 180805 0.082 213.858 Unlink 862189 0.050 172.893 Deltree 112 2.998 218.328 Mkdir 56 0.002 0.003 Qpathinfo 3870158 0.004 5.072 Qfileinfo 678375 0.001 0.194 Qfsinfo 709604 0.002 0.485 Sfileinfo 347850 0.004 1.304 Find 1496310 0.017 5.504 WriteX 2129613 0.010 2.882 ReadX 6693066 0.002 1.517 LockX 13902 0.002 0.075 UnlockX 13902 0.001 0.055 Flush 299276 2.511 220.189 Throughput 1187.33 MB/sec 8 clients 8 procs max_latency=220.194 ms +3.2% throughput, -31.8% max latency dbench with 16 clients, results before: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 5978334 0.028 156.507 Close 4391598 0.001 1.345 Rename 253136 0.241 155.057 Unlink 1207220 0.182 257.344 Deltree 160 6.123 36.277 Mkdir 80 0.003 0.005 Qpathinfo 5418817 0.012 6.867 Qfileinfo 949929 0.001 0.941 Qfsinfo 993560 0.002 1.386 Sfileinfo 486904 0.004 2.829 Find 2095088 0.059 8.164 WriteX 2982319 0.017 9.029 ReadX 9371484 0.002 4.052 LockX 19470 0.002 0.461 UnlockX 19470 0.001 0.990 Flush 418936 2.740 347.902 Throughput 1495.31 MB/sec 16 clients 16 procs max_latency=347.909 ms dbench with 16 clients, results after: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 5711833 0.029 131.240 Close 4195897 0.001 1.732 Rename 241849 0.204 147.831 Unlink 1153341 0.184 231.322 Deltree 160 6.086 30.198 Mkdir 80 0.003 0.021 Qpathinfo 5177011 0.012 7.150 Qfileinfo 907768 0.001 0.793 Qfsinfo 949205 0.002 1.431 Sfileinfo 465317 0.004 2.454 Find 2001541 0.058 7.819 WriteX 2850661 0.017 9.110 ReadX 8952289 0.002 3.991 LockX 18596 0.002 0.655 UnlockX 18596 0.001 0.179 Flush 400342 2.879 293.607 Throughput 1565.73 MB/sec 16 clients 16 procs max_latency=293.611 ms +4.6% throughput, -16.9% max latency Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>

btrfs: do not pin logs too early during renames
During renames we pin the logs of the roots a bit too early, before the calls to btrfs_insert_inode_ref(). We can pin the logs after those calls, since those will not change anything in a log tree. In a scenario where we have multiple and diverse filesystem operations running in parallel, those calls can take a significant amount of time, due to lock contention on extent buffers, and delay log commits from other tasks for longer than necessary. So just pin logs after calls to btrfs_insert_inode_ref() and right before the first operation that can update a log tree. The following script that uses dbench was used for testing: $ cat dbench-test.sh #!/bin/bash DEV=/dev/nvme0n1 MNT=/mnt/nvme0n1 MOUNT_OPTIONS="-o ssd" MKFS_OPTIONS="-m single -d single" 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 -t 120 16 umount $MNT The tests were run on a machine with 12 cores, 64G of RAN, a NVMe device and using a non-debug kernel config (Debian's default config). The results compare a branch without this patch and without the previous patch in the series, that has the subject: "btrfs: eliminate some false positives when checking if inode was logged" Versus the same branch with these two patches applied. dbench with 8 clients, results before: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 4391359 0.009 249.745 Close 3225882 0.001 3.243 Rename 185953 0.065 240.643 Unlink 886669 0.049 249.906 Deltree 112 2.455 217.433 Mkdir 56 0.002 0.004 Qpathinfo 3980281 0.004 3.109 Qfileinfo 697579 0.001 0.187 Qfsinfo 729780 0.002 2.424 Sfileinfo 357764 0.004 1.415 Find 1538861 0.016 4.863 WriteX 2189666 0.010 3.327 ReadX 6883443 0.002 0.729 LockX 14298 0.002 0.073 UnlockX 14298 0.001 0.042 Flush 307777 2.447 303.663 Throughput 1149.6 MB/sec 8 clients 8 procs max_latency=303.666 ms dbench with 8 clients, results after: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 4269920 0.009 213.532 Close 3136653 0.001 0.690 Rename 180805 0.082 213.858 Unlink 862189 0.050 172.893 Deltree 112 2.998 218.328 Mkdir 56 0.002 0.003 Qpathinfo 3870158 0.004 5.072 Qfileinfo 678375 0.001 0.194 Qfsinfo 709604 0.002 0.485 Sfileinfo 347850 0.004 1.304 Find 1496310 0.017 5.504 WriteX 2129613 0.010 2.882 ReadX 6693066 0.002 1.517 LockX 13902 0.002 0.075 UnlockX 13902 0.001 0.055 Flush 299276 2.511 220.189 Throughput 1187.33 MB/sec 8 clients 8 procs max_latency=220.194 ms +3.2% throughput, -31.8% max latency dbench with 16 clients, results before: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 5978334 0.028 156.507 Close 4391598 0.001 1.345 Rename 253136 0.241 155.057 Unlink 1207220 0.182 257.344 Deltree 160 6.123 36.277 Mkdir 80 0.003 0.005 Qpathinfo 5418817 0.012 6.867 Qfileinfo 949929 0.001 0.941 Qfsinfo 993560 0.002 1.386 Sfileinfo 486904 0.004 2.829 Find 2095088 0.059 8.164 WriteX 2982319 0.017 9.029 ReadX 9371484 0.002 4.052 LockX 19470 0.002 0.461 UnlockX 19470 0.001 0.990 Flush 418936 2.740 347.902 Throughput 1495.31 MB/sec 16 clients 16 procs max_latency=347.909 ms dbench with 16 clients, results after: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 5711833 0.029 131.240 Close 4195897 0.001 1.732 Rename 241849 0.204 147.831 Unlink 1153341 0.184 231.322 Deltree 160 6.086 30.198 Mkdir 80 0.003 0.021 Qpathinfo 5177011 0.012 7.150 Qfileinfo 907768 0.001 0.793 Qfsinfo 949205 0.002 1.431 Sfileinfo 465317 0.004 2.454 Find 2001541 0.058 7.819 WriteX 2850661 0.017 9.110 ReadX 8952289 0.002 3.991 LockX 18596 0.002 0.655 UnlockX 18596 0.001 0.179 Flush 400342 2.879 293.607 Throughput 1565.73 MB/sec 16 clients 16 procs max_latency=293.611 ms +4.6% throughput, -16.9% max latency Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
bd54f381 · Filipe Manana · David Sterba · 6e8e777d · bd54f381
Commit bd54f381 authored Jul 27, 2021 by Filipe Manana Committed by David Sterba Aug 23, 2021
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Showing with 42 additions and 6 deletions

fs/btrfs/inode.c fs/btrfs/inode.c +42 -6

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--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9350,8 +9350,6 @@ static int btrfs_rename_exchange(struct inode *old_dir,
 		/* force full log commit if subvolume involved. */
 		btrfs_set_log_full_commit(trans);
 	} else {
-		btrfs_pin_log_trans(root);
-		root_log_pinned = true;
 		ret = btrfs_insert_inode_ref(trans, dest,
 					     new_dentry->d_name.name,
 					     new_dentry->d_name.len,
@@ -9368,8 +9366,6 @@ static int btrfs_rename_exchange(struct inode *old_dir,
 		/* force full log commit if subvolume involved. */
 		btrfs_set_log_full_commit(trans);
 	} else {
-		btrfs_pin_log_trans(dest);
-		dest_log_pinned = true;
 		ret = btrfs_insert_inode_ref(trans, root,
 					     old_dentry->d_name.name,
 					     old_dentry->d_name.len,
@@ -9400,6 +9396,29 @@ static int btrfs_rename_exchange(struct inode *old_dir,
 				BTRFS_I(new_inode), 1);
 	}

+	/*
+	 * Now pin the logs of the roots. We do it to ensure that no other task
+	 * can sync the logs while we are in progress with the rename, because
+	 * that could result in an inconsistency in case any of the inodes that
+	 * are part of this rename operation were logged before.
+	 *
+	 * We pin the logs even if at this precise moment none of the inodes was
+	 * logged before. This is because right after we checked for that, some
+	 * other task fsyncing some other inode not involved with this rename
+	 * operation could log that one of our inodes exists.
+	 *
+	 * We don't need to pin the logs before the above calls to
+	 * btrfs_insert_inode_ref(), since those don't ever need to change a log.
+	 */
+	if (old_ino != BTRFS_FIRST_FREE_OBJECTID) {
+		btrfs_pin_log_trans(root);
+		root_log_pinned = true;
+	}
+	if (new_ino != BTRFS_FIRST_FREE_OBJECTID) {
+		btrfs_pin_log_trans(dest);
+		dest_log_pinned = true;
+	}
+
 	/* src is a subvolume */
 	if (old_ino == BTRFS_FIRST_FREE_OBJECTID) {
 		ret = btrfs_unlink_subvol(trans, old_dir, old_dentry);
@@ -9652,8 +9671,6 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 		/* force full log commit if subvolume involved. */
 		btrfs_set_log_full_commit(trans);
 	} else {
-		btrfs_pin_log_trans(root);
-		log_pinned = true;
 		ret = btrfs_insert_inode_ref(trans, dest,
 					     new_dentry->d_name.name,
 					     new_dentry->d_name.len,
@@ -9677,6 +9694,25 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	if (unlikely(old_ino == BTRFS_FIRST_FREE_OBJECTID)) {
 		ret = btrfs_unlink_subvol(trans, old_dir, old_dentry);
 	} else {
+		/*
+		 * Now pin the log. We do it to ensure that no other task can
+		 * sync the log while we are in progress with the rename, as
+		 * that could result in an inconsistency in case any of the
+		 * inodes that are part of this rename operation were logged
+		 * before.
+		 *
+		 * We pin the log even if at this precise moment none of the
+		 * inodes was logged before. This is because right after we
+		 * checked for that, some other task fsyncing some other inode
+		 * not involved with this rename operation could log that one of
+		 * our inodes exists.
+		 *
+		 * We don't need to pin the logs before the above call to
+		 * btrfs_insert_inode_ref(), since that does not need to change
+		 * a log.
+		 */
+		btrfs_pin_log_trans(root);
+		log_pinned = true;
 		ret = __btrfs_unlink_inode(trans, root, BTRFS_I(old_dir),
 					BTRFS_I(d_inode(old_dentry)),
 					old_dentry->d_name.name,