From: Filipe Manana Date: Wed, 5 Apr 2023 17:51:30 +0000 (+0100) Subject: btrfs: use log root when iterating over index keys when logging directory X-Git-Tag: microblaze-v6.6~262^2~35 X-Git-Url: http://git.monstr.eu/?a=commitdiff_plain;h=5d3e4f1d5123d79932177c3e7461a968f412775a;p=linux-2.6-microblaze.git btrfs: use log root when iterating over index keys when logging directory When logging dir dentries of a directory, we iterate over the subvolume tree to find dir index keys on leaves modified in the current transaction. This however is heavy on locking, since btrfs_search_forward() may often keep locks on extent buffers for quite a while when walking the tree to find a suitable leaf modified in the current transaction and with a key not smaller than then the provided minimum key. That means it will block other tasks trying to access the subvolume tree, which may be common fs operations like creating, renaming, linking, unlinking, reflinking files, etc. A better solution is to iterate the log tree, since it's much smaller than a subvolume tree and just use plain btrfs_search_slot() (or the wrapper btrfs_for_each_slot()) and only contains dir index keys added in the current transaction. The following bonnie++ test on a non-debug kernel (with Debian's default kernel config) on a 20G null block device, was used to measure the impact: $ cat test.sh #!/bin/bash DEV=/dev/nullb0 MNT=/mnt/nullb0 NR_DIRECTORIES=20 NR_FILES=20480 # must be a multiple of 1024 DATASET_SIZE=$(( (8 * 1024 * 1024 * 1024) / 1048576 )) # 8 GiB as megabytes DIRECTORY_SIZE=$(( DATASET_SIZE / NR_FILES )) NR_FILES=$(( NR_FILES / 1024 )) umount $DEV &> /dev/null mkfs.btrfs -f $DEV mount $DEV $MNT bonnie++ -u root -d $MNT \ -n $NR_FILES:$DIRECTORY_SIZE:$DIRECTORY_SIZE:$NR_DIRECTORIES \ -r 0 -s $DATASET_SIZE -b umount $MNT Before patchset: Version 2.00a ------Sequential Output------ --Sequential Input- --Random- -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Name:Size etc /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP debian0 8G 376k 99 1.1g 98 939m 92 1527k 99 3.2g 99 9060 256 Latency 24920us 207us 680ms 5594us 171us 2891us Version 2.00a ------Sequential Create------ --------Random Create-------- debian0 -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 20/20 20480 96 +++++ +++ 20480 95 20480 99 +++++ +++ 20480 97 Latency 8708us 137us 5128us 6743us 60us 19712us After patchset: Version 2.00a ------Sequential Output------ --Sequential Input- --Random- -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Name:Size etc /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP debian0 8G 384k 99 1.2g 99 971m 91 1533k 99 3.3g 99 9180 309 Latency 24930us 125us 661ms 5587us 46us 2020us Version 2.00a ------Sequential Create------ --------Random Create-------- debian0 -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 20/20 20480 90 +++++ +++ 20480 99 20480 99 +++++ +++ 20480 97 Latency 7030us 61us 1246us 4942us 56us 16855us The patchset consists of this patch plus a previous one that has the following subject: "btrfs: avoid iterating over all indexes when logging directory" Signed-off-by: Filipe Manana Signed-off-by: David Sterba --- diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index d746ebf841fd..9b212e8c70cc 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -5399,45 +5399,34 @@ static int log_new_dir_dentries(struct btrfs_trans_handle *trans, while (true) { struct inode *vfs_inode; - struct extent_buffer *leaf; - struct btrfs_key min_key; + struct btrfs_key key; + struct btrfs_key found_key; u64 next_index; bool continue_curr_inode = true; - int nritems; - int i; + int iter_ret; - min_key.objectid = ino; - min_key.type = BTRFS_DIR_INDEX_KEY; - min_key.offset = btrfs_get_first_dir_index_to_log(curr_inode); - next_index = min_key.offset; + key.objectid = ino; + key.type = BTRFS_DIR_INDEX_KEY; + key.offset = btrfs_get_first_dir_index_to_log(curr_inode); + next_index = key.offset; again: - ret = btrfs_search_forward(root, &min_key, path, trans->transid); - if (ret < 0) { - break; - } else if (ret > 0) { - ret = 0; - goto next; - } - - leaf = path->nodes[0]; - nritems = btrfs_header_nritems(leaf); - for (i = path->slots[0]; i < nritems; i++) { + btrfs_for_each_slot(root->log_root, &key, &found_key, path, iter_ret) { + struct extent_buffer *leaf = path->nodes[0]; struct btrfs_dir_item *di; struct btrfs_key di_key; struct inode *di_inode; int log_mode = LOG_INODE_EXISTS; int type; - btrfs_item_key_to_cpu(leaf, &min_key, i); - if (min_key.objectid != ino || - min_key.type != BTRFS_DIR_INDEX_KEY) { + if (found_key.objectid != ino || + found_key.type != BTRFS_DIR_INDEX_KEY) { continue_curr_inode = false; break; } - next_index = min_key.offset + 1; + next_index = found_key.offset + 1; - di = btrfs_item_ptr(leaf, i, struct btrfs_dir_item); + di = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dir_item); type = btrfs_dir_ftype(leaf, di); if (btrfs_dir_transid(leaf, di) < trans->transid) continue; @@ -5479,12 +5468,20 @@ again: btrfs_release_path(path); - if (continue_curr_inode && min_key.offset < (u64)-1) { - min_key.offset++; + if (iter_ret < 0) { + ret = iter_ret; + goto out; + } else if (iter_ret > 0) { + continue_curr_inode = false; + } else { + key = found_key; + } + + if (continue_curr_inode && key.offset < (u64)-1) { + key.offset++; goto again; } -next: btrfs_set_first_dir_index_to_log(curr_inode, next_index); if (list_empty(&dir_list))