From: Filipe Manana fdmanana@suse.com
[ Upstream commit 75b463d2b47aef96fe1dc3e0237629963034764b ]
Since commit d4682ba03ef618 ("Btrfs: sync log after logging new name") we started to commit logs, and fallback to transaction commits when we failed to log the new names or commit the logs, after link and rename operations when the target inodes (or their parents) were previously logged in the current transaction. This was to avoid losing directories despite an explicit fsync on them when they are ancestors of some inode that got a new named logged, due to a link or rename operation. However that adds the cost of starting IO and waiting for it to complete, which can cause higher latencies for applications.
Instead of doing that, just make sure that when we log a new name for an inode we don't mark any of its ancestors as logged, so that if any one does an fsync against any of them, without doing any other change on them, the fsync commits the log. This way we only pay the cost of a log commit (or a transaction commit if something goes wrong or a new block group was created) if the application explicitly asks to fsync any of the parent directories.
Using dbench, which mixes several filesystems operations including renames, revealed some significant latency gains. The following script that uses dbench was used to test this:
#!/bin/bash
DEV=/dev/nvme0n1 MNT=/mnt/btrfs MOUNT_OPTIONS="-o ssd -o space_cache=v2" MKFS_OPTIONS="-m single -d single" THREADS=16
echo "performance" | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor mkfs.btrfs -f $MKFS_OPTIONS $DEV mount $MOUNT_OPTIONS $DEV $MNT
dbench -t 300 -D $MNT $THREADS
umount $MNT
The test was run on bare metal, no virtualization, on a box with 12 cores (Intel i7-8700), 64Gb of RAM and using a NVMe device, with a kernel configuration that is the default of typical distributions (debian in this case), without debug options enabled (kasan, kmemleak, slub debug, debug of page allocations, lock debugging, etc).
Results before this patch:
Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 10750455 0.011 155.088 Close 7896674 0.001 0.243 Rename 455222 2.158 1101.947 Unlink 2171189 0.067 121.638 Deltree 256 2.425 7.816 Mkdir 128 0.002 0.003 Qpathinfo 9744323 0.006 21.370 Qfileinfo 1707092 0.001 0.146 Qfsinfo 1786756 0.001 11.228 Sfileinfo 875612 0.003 21.263 Find 3767281 0.025 9.617 WriteX 5356924 0.011 211.390 ReadX 16852694 0.003 9.442 LockX 35008 0.002 0.119 UnlockX 35008 0.001 0.138 Flush 753458 4.252 1102.249
Throughput 1128.35 MB/sec 16 clients 16 procs max_latency=1102.255 ms
Results after this patch:
16 clients, after
Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 11471098 0.012 448.281 Close 8426396 0.001 0.925 Rename 485746 0.123 267.183 Unlink 2316477 0.080 63.433 Deltree 288 2.830 11.144 Mkdir 144 0.003 0.010 Qpathinfo 10397420 0.006 10.288 Qfileinfo 1822039 0.001 0.169 Qfsinfo 1906497 0.002 14.039 Sfileinfo 934433 0.004 2.438 Find 4019879 0.026 10.200 WriteX 5718932 0.011 200.985 ReadX 17981671 0.003 10.036 LockX 37352 0.002 0.076 UnlockX 37352 0.001 0.109 Flush 804018 5.015 778.033
Throughput 1201.98 MB/sec 16 clients 16 procs max_latency=778.036 ms (+6.5% throughput, -29.4% max latency, -75.8% rename latency)
Test case generic/498 from fstests tests the scenario that the previously mentioned commit fixed.
Signed-off-by: Filipe Manana fdmanana@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/inode.c | 115 +++++--------------------------------------- fs/btrfs/tree-log.c | 100 +++++++++++++++++--------------------- fs/btrfs/tree-log.h | 14 ++---- 3 files changed, 60 insertions(+), 169 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 025b02e9799f..8959d011aafa 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -6992,7 +6992,6 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir, drop_inode = 1; } else { struct dentry *parent = dentry->d_parent; - int ret;
err = btrfs_update_inode(trans, root, inode); if (err) @@ -7007,12 +7006,7 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir, goto fail; } d_instantiate(dentry, inode); - ret = btrfs_log_new_name(trans, BTRFS_I(inode), NULL, parent, - true, NULL); - if (ret == BTRFS_NEED_TRANS_COMMIT) { - err = btrfs_commit_transaction(trans); - trans = NULL; - } + btrfs_log_new_name(trans, BTRFS_I(inode), NULL, parent); }
fail: @@ -9699,27 +9693,19 @@ static int btrfs_rename_exchange(struct inode *old_dir, struct inode *new_inode = new_dentry->d_inode; struct inode *old_inode = old_dentry->d_inode; struct timespec64 ctime = current_time(old_inode); - struct dentry *parent; u64 old_ino = btrfs_ino(BTRFS_I(old_inode)); u64 new_ino = btrfs_ino(BTRFS_I(new_inode)); u64 old_idx = 0; u64 new_idx = 0; int ret; + int ret2; bool root_log_pinned = false; bool dest_log_pinned = false; - struct btrfs_log_ctx ctx_root; - struct btrfs_log_ctx ctx_dest; - bool sync_log_root = false; - bool sync_log_dest = false; - bool commit_transaction = false;
/* we only allow rename subvolume link between subvolumes */ if (old_ino != BTRFS_FIRST_FREE_OBJECTID && root != dest) return -EXDEV;
- btrfs_init_log_ctx(&ctx_root, old_inode); - btrfs_init_log_ctx(&ctx_dest, new_inode); - /* close the race window with snapshot create/destroy ioctl */ if (old_ino == BTRFS_FIRST_FREE_OBJECTID || new_ino == BTRFS_FIRST_FREE_OBJECTID) @@ -9861,30 +9847,14 @@ static int btrfs_rename_exchange(struct inode *old_dir, BTRFS_I(new_inode)->dir_index = new_idx;
if (root_log_pinned) { - parent = new_dentry->d_parent; - ret = btrfs_log_new_name(trans, BTRFS_I(old_inode), - BTRFS_I(old_dir), parent, - false, &ctx_root); - if (ret == BTRFS_NEED_LOG_SYNC) - sync_log_root = true; - else if (ret == BTRFS_NEED_TRANS_COMMIT) - commit_transaction = true; - ret = 0; + btrfs_log_new_name(trans, BTRFS_I(old_inode), BTRFS_I(old_dir), + new_dentry->d_parent); btrfs_end_log_trans(root); root_log_pinned = false; } if (dest_log_pinned) { - if (!commit_transaction) { - parent = old_dentry->d_parent; - ret = btrfs_log_new_name(trans, BTRFS_I(new_inode), - BTRFS_I(new_dir), parent, - false, &ctx_dest); - if (ret == BTRFS_NEED_LOG_SYNC) - sync_log_dest = true; - else if (ret == BTRFS_NEED_TRANS_COMMIT) - commit_transaction = true; - ret = 0; - } + btrfs_log_new_name(trans, BTRFS_I(new_inode), BTRFS_I(new_dir), + old_dentry->d_parent); btrfs_end_log_trans(dest); dest_log_pinned = false; } @@ -9917,46 +9887,13 @@ static int btrfs_rename_exchange(struct inode *old_dir, dest_log_pinned = false; } } - if (!ret && sync_log_root && !commit_transaction) { - ret = btrfs_sync_log(trans, BTRFS_I(old_inode)->root, - &ctx_root); - if (ret) - commit_transaction = true; - } - if (!ret && sync_log_dest && !commit_transaction) { - ret = btrfs_sync_log(trans, BTRFS_I(new_inode)->root, - &ctx_dest); - if (ret) - commit_transaction = true; - } - if (commit_transaction) { - /* - * We may have set commit_transaction when logging the new name - * in the destination root, in which case we left the source - * root context in the list of log contextes. So make sure we - * remove it to avoid invalid memory accesses, since the context - * was allocated in our stack frame. - */ - if (sync_log_root) { - mutex_lock(&root->log_mutex); - list_del_init(&ctx_root.list); - mutex_unlock(&root->log_mutex); - } - ret = btrfs_commit_transaction(trans); - } else { - int ret2; - - ret2 = btrfs_end_transaction(trans); - ret = ret ? ret : ret2; - } + ret2 = btrfs_end_transaction(trans); + ret = ret ? ret : ret2; out_notrans: if (new_ino == BTRFS_FIRST_FREE_OBJECTID || old_ino == BTRFS_FIRST_FREE_OBJECTID) up_read(&fs_info->subvol_sem);
- ASSERT(list_empty(&ctx_root.list)); - ASSERT(list_empty(&ctx_dest.list)); - return ret; }
@@ -10024,11 +9961,9 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *old_inode = d_inode(old_dentry); u64 index = 0; int ret; + int ret2; u64 old_ino = btrfs_ino(BTRFS_I(old_inode)); bool log_pinned = false; - struct btrfs_log_ctx ctx; - bool sync_log = false; - bool commit_transaction = false;
if (btrfs_ino(BTRFS_I(new_dir)) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID) return -EPERM; @@ -10178,17 +10113,8 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry, BTRFS_I(old_inode)->dir_index = index;
if (log_pinned) { - struct dentry *parent = new_dentry->d_parent; - - btrfs_init_log_ctx(&ctx, old_inode); - ret = btrfs_log_new_name(trans, BTRFS_I(old_inode), - BTRFS_I(old_dir), parent, - false, &ctx); - if (ret == BTRFS_NEED_LOG_SYNC) - sync_log = true; - else if (ret == BTRFS_NEED_TRANS_COMMIT) - commit_transaction = true; - ret = 0; + btrfs_log_new_name(trans, BTRFS_I(old_inode), BTRFS_I(old_dir), + new_dentry->d_parent); btrfs_end_log_trans(root); log_pinned = false; } @@ -10225,23 +10151,8 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry, btrfs_end_log_trans(root); log_pinned = false; } - if (!ret && sync_log) { - ret = btrfs_sync_log(trans, BTRFS_I(old_inode)->root, &ctx); - if (ret) - commit_transaction = true; - } else if (sync_log) { - mutex_lock(&root->log_mutex); - list_del(&ctx.list); - mutex_unlock(&root->log_mutex); - } - if (commit_transaction) { - ret = btrfs_commit_transaction(trans); - } else { - int ret2; - - ret2 = btrfs_end_transaction(trans); - ret = ret ? ret : ret2; - } + ret2 = btrfs_end_transaction(trans); + ret = ret ? ret : ret2; out_notrans: if (old_ino == BTRFS_FIRST_FREE_OBJECTID) up_read(&fs_info->subvol_sem); diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index dcbdd0ebea83..53607156b008 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -174,7 +174,7 @@ static int start_log_trans(struct btrfs_trans_handle *trans,
atomic_inc(&root->log_batch); atomic_inc(&root->log_writers); - if (ctx) { + if (ctx && !ctx->logging_new_name) { int index = root->log_transid % 2; list_add_tail(&ctx->list, &root->log_ctxs[index]); ctx->log_transid = root->log_transid; @@ -5379,19 +5379,34 @@ static int btrfs_log_inode(struct btrfs_trans_handle *trans, }
/* - * Don't update last_log_commit if we logged that an inode exists after - * it was loaded to memory (full_sync bit set). - * This is to prevent data loss when we do a write to the inode, then - * the inode gets evicted after all delalloc was flushed, then we log - * it exists (due to a rename for example) and then fsync it. This last - * fsync would do nothing (not logging the extents previously written). + * If we are logging that an ancestor inode exists as part of logging a + * new name from a link or rename operation, don't mark the inode as + * logged - otherwise if an explicit fsync is made against an ancestor, + * the fsync considers the inode in the log and doesn't sync the log, + * resulting in the ancestor missing after a power failure unless the + * log was synced as part of an fsync against any other unrelated inode. + * So keep it simple for this case and just don't flag the ancestors as + * logged. */ - spin_lock(&inode->lock); - inode->logged_trans = trans->transid; - if (inode_only != LOG_INODE_EXISTS || - !test_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &inode->runtime_flags)) - inode->last_log_commit = inode->last_sub_trans; - spin_unlock(&inode->lock); + if (!ctx || + !(S_ISDIR(inode->vfs_inode.i_mode) && ctx->logging_new_name && + &inode->vfs_inode != ctx->inode)) { + spin_lock(&inode->lock); + inode->logged_trans = trans->transid; + /* + * Don't update last_log_commit if we logged that an inode exists + * after it was loaded to memory (full_sync bit set). + * This is to prevent data loss when we do a write to the inode, + * then the inode gets evicted after all delalloc was flushed, + * then we log it exists (due to a rename for example) and then + * fsync it. This last fsync would do nothing (not logging the + * extents previously written). + */ + if (inode_only != LOG_INODE_EXISTS || + !test_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &inode->runtime_flags)) + inode->last_log_commit = inode->last_sub_trans; + spin_unlock(&inode->lock); + } out_unlock: mutex_unlock(&inode->log_mutex);
@@ -6417,26 +6432,13 @@ void btrfs_record_snapshot_destroy(struct btrfs_trans_handle *trans, /* * Call this after adding a new name for a file and it will properly * update the log to reflect the new name. - * - * @ctx can not be NULL when @sync_log is false, and should be NULL when it's - * true (because it's not used). - * - * Return value depends on whether @sync_log is true or false. - * When true: returns BTRFS_NEED_TRANS_COMMIT if the transaction needs to be - * committed by the caller, and BTRFS_DONT_NEED_TRANS_COMMIT - * otherwise. - * When false: returns BTRFS_DONT_NEED_LOG_SYNC if the caller does not need to - * sync the log, BTRFS_NEED_LOG_SYNC if it needs to sync the log, - * or BTRFS_NEED_TRANS_COMMIT if the transaction needs to be - * committed (without attempting to sync the log). */ -int btrfs_log_new_name(struct btrfs_trans_handle *trans, +void btrfs_log_new_name(struct btrfs_trans_handle *trans, struct btrfs_inode *inode, struct btrfs_inode *old_dir, - struct dentry *parent, - bool sync_log, struct btrfs_log_ctx *ctx) + struct dentry *parent) { struct btrfs_fs_info *fs_info = trans->fs_info; - int ret; + struct btrfs_log_ctx ctx;
/* * this will force the logging code to walk the dentry chain @@ -6451,34 +6453,18 @@ int btrfs_log_new_name(struct btrfs_trans_handle *trans, */ if (inode->logged_trans <= fs_info->last_trans_committed && (!old_dir || old_dir->logged_trans <= fs_info->last_trans_committed)) - return sync_log ? BTRFS_DONT_NEED_TRANS_COMMIT : - BTRFS_DONT_NEED_LOG_SYNC; - - if (sync_log) { - struct btrfs_log_ctx ctx2; - - btrfs_init_log_ctx(&ctx2, &inode->vfs_inode); - ret = btrfs_log_inode_parent(trans, inode, parent, 0, LLONG_MAX, - LOG_INODE_EXISTS, &ctx2); - if (ret == BTRFS_NO_LOG_SYNC) - return BTRFS_DONT_NEED_TRANS_COMMIT; - else if (ret) - return BTRFS_NEED_TRANS_COMMIT; - - ret = btrfs_sync_log(trans, inode->root, &ctx2); - if (ret) - return BTRFS_NEED_TRANS_COMMIT; - return BTRFS_DONT_NEED_TRANS_COMMIT; - } - - ASSERT(ctx); - ret = btrfs_log_inode_parent(trans, inode, parent, 0, LLONG_MAX, - LOG_INODE_EXISTS, ctx); - if (ret == BTRFS_NO_LOG_SYNC) - return BTRFS_DONT_NEED_LOG_SYNC; - else if (ret) - return BTRFS_NEED_TRANS_COMMIT; + return;
- return BTRFS_NEED_LOG_SYNC; + btrfs_init_log_ctx(&ctx, &inode->vfs_inode); + ctx.logging_new_name = true; + /* + * We don't care about the return value. If we fail to log the new name + * then we know the next attempt to sync the log will fallback to a full + * transaction commit (due to a call to btrfs_set_log_full_commit()), so + * we don't need to worry about getting a log committed that has an + * inconsistent state after a rename operation. + */ + btrfs_log_inode_parent(trans, inode, parent, 0, LLONG_MAX, + LOG_INODE_EXISTS, &ctx); }
diff --git a/fs/btrfs/tree-log.h b/fs/btrfs/tree-log.h index 132e43d29034..ddfc6789d9bf 100644 --- a/fs/btrfs/tree-log.h +++ b/fs/btrfs/tree-log.h @@ -16,6 +16,7 @@ struct btrfs_log_ctx { int log_ret; int log_transid; bool log_new_dentries; + bool logging_new_name; struct inode *inode; struct list_head list; }; @@ -26,6 +27,7 @@ static inline void btrfs_init_log_ctx(struct btrfs_log_ctx *ctx, ctx->log_ret = 0; ctx->log_transid = 0; ctx->log_new_dentries = false; + ctx->logging_new_name = false; ctx->inode = inode; INIT_LIST_HEAD(&ctx->list); } @@ -67,16 +69,8 @@ void btrfs_record_unlink_dir(struct btrfs_trans_handle *trans, int for_rename); void btrfs_record_snapshot_destroy(struct btrfs_trans_handle *trans, struct btrfs_inode *dir); -/* Return values for btrfs_log_new_name() */ -enum { - BTRFS_DONT_NEED_TRANS_COMMIT, - BTRFS_NEED_TRANS_COMMIT, - BTRFS_DONT_NEED_LOG_SYNC, - BTRFS_NEED_LOG_SYNC, -}; -int btrfs_log_new_name(struct btrfs_trans_handle *trans, +void btrfs_log_new_name(struct btrfs_trans_handle *trans, struct btrfs_inode *inode, struct btrfs_inode *old_dir, - struct dentry *parent, - bool sync_log, struct btrfs_log_ctx *ctx); + struct dentry *parent);
#endif