diff options
Diffstat (limited to 'fs/btrfs/delalloc-space.c')
| -rw-r--r-- | fs/btrfs/delalloc-space.c | 142 |
1 files changed, 120 insertions, 22 deletions
diff --git a/fs/btrfs/delalloc-space.c b/fs/btrfs/delalloc-space.c index 4cdac4d834f5..0e354e9e57d0 100644 --- a/fs/btrfs/delalloc-space.c +++ b/fs/btrfs/delalloc-space.c @@ -9,6 +9,108 @@ #include "qgroup.h" #include "block-group.h" +/* + * HOW DOES THIS WORK + * + * There are two stages to data reservations, one for data and one for metadata + * to handle the new extents and checksums generated by writing data. + * + * + * DATA RESERVATION + * The general flow of the data reservation is as follows + * + * -> Reserve + * We call into btrfs_reserve_data_bytes() for the user request bytes that + * they wish to write. We make this reservation and add it to + * space_info->bytes_may_use. We set EXTENT_DELALLOC on the inode io_tree + * for the range and carry on if this is buffered, or follow up trying to + * make a real allocation if we are pre-allocating or doing O_DIRECT. + * + * -> Use + * At writepages()/prealloc/O_DIRECT time we will call into + * btrfs_reserve_extent() for some part or all of this range of bytes. We + * will make the allocation and subtract space_info->bytes_may_use by the + * original requested length and increase the space_info->bytes_reserved by + * the allocated length. This distinction is important because compression + * may allocate a smaller on disk extent than we previously reserved. + * + * -> Allocation + * finish_ordered_io() will insert the new file extent item for this range, + * and then add a delayed ref update for the extent tree. Once that delayed + * ref is written the extent size is subtracted from + * space_info->bytes_reserved and added to space_info->bytes_used. + * + * Error handling + * + * -> By the reservation maker + * This is the simplest case, we haven't completed our operation and we know + * how much we reserved, we can simply call + * btrfs_free_reserved_data_space*() and it will be removed from + * space_info->bytes_may_use. + * + * -> After the reservation has been made, but before cow_file_range() + * This is specifically for the delalloc case. You must clear + * EXTENT_DELALLOC with the EXTENT_CLEAR_DATA_RESV bit, and the range will + * be subtracted from space_info->bytes_may_use. + * + * METADATA RESERVATION + * The general metadata reservation lifetimes are discussed elsewhere, this + * will just focus on how it is used for delalloc space. + * + * We keep track of two things on a per inode bases + * + * ->outstanding_extents + * This is the number of file extent items we'll need to handle all of the + * outstanding DELALLOC space we have in this inode. We limit the maximum + * size of an extent, so a large contiguous dirty area may require more than + * one outstanding_extent, which is why count_max_extents() is used to + * determine how many outstanding_extents get added. + * + * ->csum_bytes + * This is essentially how many dirty bytes we have for this inode, so we + * can calculate the number of checksum items we would have to add in order + * to checksum our outstanding data. + * + * We keep a per-inode block_rsv in order to make it easier to keep track of + * our reservation. We use btrfs_calculate_inode_block_rsv_size() to + * calculate the current theoretical maximum reservation we would need for the + * metadata for this inode. We call this and then adjust our reservation as + * necessary, either by attempting to reserve more space, or freeing up excess + * space. + * + * OUTSTANDING_EXTENTS HANDLING + * + * ->outstanding_extents is used for keeping track of how many extents we will + * need to use for this inode, and it will fluctuate depending on where you are + * in the life cycle of the dirty data. Consider the following normal case for + * a completely clean inode, with a num_bytes < our maximum allowed extent size + * + * -> reserve + * ->outstanding_extents += 1 (current value is 1) + * + * -> set_delalloc + * ->outstanding_extents += 1 (currrent value is 2) + * + * -> btrfs_delalloc_release_extents() + * ->outstanding_extents -= 1 (current value is 1) + * + * We must call this once we are done, as we hold our reservation for the + * duration of our operation, and then assume set_delalloc will update the + * counter appropriately. + * + * -> add ordered extent + * ->outstanding_extents += 1 (current value is 2) + * + * -> btrfs_clear_delalloc_extent + * ->outstanding_extents -= 1 (current value is 1) + * + * -> finish_ordered_io/btrfs_remove_ordered_extent + * ->outstanding_extents -= 1 (current value is 0) + * + * Each stage is responsible for their own accounting of the extent, thus + * making error handling and cleanup easier. + */ + int btrfs_alloc_data_chunk_ondemand(struct btrfs_inode *inode, u64 bytes) { struct btrfs_root *root = inode->root; @@ -135,10 +237,10 @@ commit_trans: return 0; } -int btrfs_check_data_free_space(struct inode *inode, +int btrfs_check_data_free_space(struct btrfs_inode *inode, struct extent_changeset **reserved, u64 start, u64 len) { - struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); + struct btrfs_fs_info *fs_info = inode->root->fs_info; int ret; /* align the range */ @@ -146,14 +248,14 @@ int btrfs_check_data_free_space(struct inode *inode, round_down(start, fs_info->sectorsize); start = round_down(start, fs_info->sectorsize); - ret = btrfs_alloc_data_chunk_ondemand(BTRFS_I(inode), len); + ret = btrfs_alloc_data_chunk_ondemand(inode, len); if (ret < 0) return ret; /* Use new btrfs_qgroup_reserve_data to reserve precious data space. */ ret = btrfs_qgroup_reserve_data(inode, reserved, start, len); if (ret < 0) - btrfs_free_reserved_data_space_noquota(inode, start, len); + btrfs_free_reserved_data_space_noquota(fs_info, len); else ret = 0; return ret; @@ -167,16 +269,12 @@ int btrfs_check_data_free_space(struct inode *inode, * which we can't sleep and is sure it won't affect qgroup reserved space. * Like clear_bit_hook(). */ -void btrfs_free_reserved_data_space_noquota(struct inode *inode, u64 start, +void btrfs_free_reserved_data_space_noquota(struct btrfs_fs_info *fs_info, u64 len) { - struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); struct btrfs_space_info *data_sinfo; - /* Make sure the range is aligned to sectorsize */ - len = round_up(start + len, fs_info->sectorsize) - - round_down(start, fs_info->sectorsize); - start = round_down(start, fs_info->sectorsize); + ASSERT(IS_ALIGNED(len, fs_info->sectorsize)); data_sinfo = fs_info->data_sinfo; spin_lock(&data_sinfo->lock); @@ -191,17 +289,17 @@ void btrfs_free_reserved_data_space_noquota(struct inode *inode, u64 start, * This one will handle the per-inode data rsv map for accurate reserved * space framework. */ -void btrfs_free_reserved_data_space(struct inode *inode, +void btrfs_free_reserved_data_space(struct btrfs_inode *inode, struct extent_changeset *reserved, u64 start, u64 len) { - struct btrfs_root *root = BTRFS_I(inode)->root; + struct btrfs_fs_info *fs_info = inode->root->fs_info; /* Make sure the range is aligned to sectorsize */ - len = round_up(start + len, root->fs_info->sectorsize) - - round_down(start, root->fs_info->sectorsize); - start = round_down(start, root->fs_info->sectorsize); + len = round_up(start + len, fs_info->sectorsize) - + round_down(start, fs_info->sectorsize); + start = round_down(start, fs_info->sectorsize); - btrfs_free_reserved_data_space_noquota(inode, start, len); + btrfs_free_reserved_data_space_noquota(fs_info, len); btrfs_qgroup_free_data(inode, reserved, start, len); } @@ -228,8 +326,8 @@ static void btrfs_inode_rsv_release(struct btrfs_inode *inode, bool qgroup_free) * are releasing 0 bytes, and then we'll just get the reservation over * the size free'd. */ - released = __btrfs_block_rsv_release(fs_info, block_rsv, 0, - &qgroup_to_release); + released = btrfs_block_rsv_release(fs_info, block_rsv, 0, + &qgroup_to_release); if (released > 0) trace_btrfs_space_reservation(fs_info, "delalloc", btrfs_ino(inode), released, 0); @@ -455,7 +553,7 @@ void btrfs_delalloc_release_extents(struct btrfs_inode *inode, u64 num_bytes) * Return 0 for success * Return <0 for error(-ENOSPC or -EQUOT) */ -int btrfs_delalloc_reserve_space(struct inode *inode, +int btrfs_delalloc_reserve_space(struct btrfs_inode *inode, struct extent_changeset **reserved, u64 start, u64 len) { int ret; @@ -463,7 +561,7 @@ int btrfs_delalloc_reserve_space(struct inode *inode, ret = btrfs_check_data_free_space(inode, reserved, start, len); if (ret < 0) return ret; - ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode), len); + ret = btrfs_delalloc_reserve_metadata(inode, len); if (ret < 0) btrfs_free_reserved_data_space(inode, *reserved, start, len); return ret; @@ -481,10 +579,10 @@ int btrfs_delalloc_reserve_space(struct inode *inode, * list if there are no delalloc bytes left. * Also it will handle the qgroup reserved space. */ -void btrfs_delalloc_release_space(struct inode *inode, +void btrfs_delalloc_release_space(struct btrfs_inode *inode, struct extent_changeset *reserved, u64 start, u64 len, bool qgroup_free) { - btrfs_delalloc_release_metadata(BTRFS_I(inode), len, qgroup_free); + btrfs_delalloc_release_metadata(inode, len, qgroup_free); btrfs_free_reserved_data_space(inode, reserved, start, len); } |