diff options
Diffstat (limited to 'fs/btrfs/extent_map.c')
| -rw-r--r-- | fs/btrfs/extent_map.c | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c index 031c124c514c..62a21491c044 100644 --- a/fs/btrfs/extent_map.c +++ b/fs/btrfs/extent_map.c @@ -8,6 +8,7 @@ #include "extent_map.h" #include "compression.h" #include "btrfs_inode.h" +#include "disk-io.h" static struct kmem_cache *extent_map_cache; @@ -1026,3 +1027,162 @@ out_free_pre: free_extent_map(split_pre); return ret; } + +static long btrfs_scan_inode(struct btrfs_inode *inode, long *scanned, long nr_to_scan) +{ + const u64 cur_fs_gen = btrfs_get_fs_generation(inode->root->fs_info); + struct extent_map_tree *tree = &inode->extent_tree; + long nr_dropped = 0; + struct rb_node *node; + + /* + * Take the mmap lock so that we serialize with the inode logging phase + * of fsync because we may need to set the full sync flag on the inode, + * in case we have to remove extent maps in the tree's list of modified + * extents. If we set the full sync flag in the inode while an fsync is + * in progress, we may risk missing new extents because before the flag + * is set, fsync decides to only wait for writeback to complete and then + * during inode logging it sees the flag set and uses the subvolume tree + * to find new extents, which may not be there yet because ordered + * extents haven't completed yet. + * + * We also do a try lock because otherwise we could deadlock. This is + * because the shrinker for this filesystem may be invoked while we are + * in a path that is holding the mmap lock in write mode. For example in + * a reflink operation while COWing an extent buffer, when allocating + * pages for a new extent buffer and under memory pressure, the shrinker + * may be invoked, and therefore we would deadlock by attempting to read + * lock the mmap lock while we are holding already a write lock on it. + */ + if (!down_read_trylock(&inode->i_mmap_lock)) + return 0; + + write_lock(&tree->lock); + node = rb_first_cached(&tree->map); + while (node) { + struct extent_map *em; + + em = rb_entry(node, struct extent_map, rb_node); + node = rb_next(node); + (*scanned)++; + + if (em->flags & EXTENT_FLAG_PINNED) + goto next; + + /* + * If the inode is in the list of modified extents (new) and its + * generation is the same (or is greater than) the current fs + * generation, it means it was not yet persisted so we have to + * set the full sync flag so that the next fsync will not miss + * it. + */ + if (!list_empty(&em->list) && em->generation >= cur_fs_gen) + btrfs_set_inode_full_sync(inode); + + remove_extent_mapping(inode, em); + /* Drop the reference for the tree. */ + free_extent_map(em); + nr_dropped++; +next: + if (*scanned >= nr_to_scan) + break; + + /* + * Restart if we had to reschedule, and any extent maps that were + * pinned before may have become unpinned after we released the + * lock and took it again. + */ + if (cond_resched_rwlock_write(&tree->lock)) + node = rb_first_cached(&tree->map); + } + write_unlock(&tree->lock); + up_read(&inode->i_mmap_lock); + + return nr_dropped; +} + +static long btrfs_scan_root(struct btrfs_root *root, long *scanned, long nr_to_scan) +{ + struct btrfs_fs_info *fs_info = root->fs_info; + struct btrfs_inode *inode; + long nr_dropped = 0; + u64 min_ino = fs_info->extent_map_shrinker_last_ino + 1; + + inode = btrfs_find_first_inode(root, min_ino); + while (inode) { + nr_dropped += btrfs_scan_inode(inode, scanned, nr_to_scan); + + min_ino = btrfs_ino(inode) + 1; + fs_info->extent_map_shrinker_last_ino = btrfs_ino(inode); + iput(&inode->vfs_inode); + + if (*scanned >= nr_to_scan) + break; + + cond_resched(); + inode = btrfs_find_first_inode(root, min_ino); + } + + if (inode) { + /* + * There are still inodes in this root or we happened to process + * the last one and reached the scan limit. In either case set + * the current root to this one, so we'll resume from the next + * inode if there is one or we will find out this was the last + * one and move to the next root. + */ + fs_info->extent_map_shrinker_last_root = btrfs_root_id(root); + } else { + /* + * No more inodes in this root, set extent_map_shrinker_last_ino to 0 so + * that when processing the next root we start from its first inode. + */ + fs_info->extent_map_shrinker_last_ino = 0; + fs_info->extent_map_shrinker_last_root = btrfs_root_id(root) + 1; + } + + return nr_dropped; +} + +long btrfs_free_extent_maps(struct btrfs_fs_info *fs_info, long nr_to_scan) +{ + const u64 start_root_id = fs_info->extent_map_shrinker_last_root; + u64 next_root_id = start_root_id; + bool cycled = false; + long nr_dropped = 0; + long scanned = 0; + + while (scanned < nr_to_scan) { + struct btrfs_root *root; + unsigned long count; + + spin_lock(&fs_info->fs_roots_radix_lock); + count = radix_tree_gang_lookup(&fs_info->fs_roots_radix, + (void **)&root, + (unsigned long)next_root_id, 1); + if (count == 0) { + spin_unlock(&fs_info->fs_roots_radix_lock); + if (start_root_id > 0 && !cycled) { + next_root_id = 0; + fs_info->extent_map_shrinker_last_root = 0; + fs_info->extent_map_shrinker_last_ino = 0; + cycled = true; + continue; + } + break; + } + next_root_id = btrfs_root_id(root) + 1; + root = btrfs_grab_root(root); + spin_unlock(&fs_info->fs_roots_radix_lock); + + if (!root) + continue; + + if (is_fstree(btrfs_root_id(root))) + nr_dropped += btrfs_scan_root(root, &scanned, nr_to_scan); + + btrfs_put_root(root); + } + + return nr_dropped; +} |