From: amir73il@users.sourceforge.net Subject: [PATCH v1 33/36] ext4: snapshot cleanup Date: Tue, 7 Jun 2011 18:08:00 +0300 Message-ID: <1307459283-22130-34-git-send-email-amir73il@users.sourceforge.net> References: <1307459283-22130-1-git-send-email-amir73il@users.sourceforge.net> Cc: tytso@mit.edu, lczerner@redhat.com, Amir Goldstein , Yongqiang Yang To: linux-ext4@vger.kernel.org Return-path: Received: from mail-ww0-f42.google.com ([74.125.82.42]:51987 "EHLO mail-ww0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751130Ab1FGPK1 (ORCPT ); Tue, 7 Jun 2011 11:10:27 -0400 Received: by wwk4 with SMTP id 4so2575454wwk.1 for ; Tue, 07 Jun 2011 08:10:26 -0700 (PDT) In-Reply-To: <1307459283-22130-1-git-send-email-amir73il@users.sourceforge.net> Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Amir Goldstein Cleanup snapshots list and reclaim unused blocks of deleted snapshots. Oldest snapshot can be removed from list and its blocks can be freed. Non-oldest snapshots have to be shrunk and merged before they can be removed from the list. All snapshot blocks must be excluded in order to properly shrink/merge deleted old snapshots. Signed-off-by: Amir Goldstein Signed-off-by: Yongqiang Yang --- fs/ext4/ext4.h | 16 ++++++++ fs/ext4/inode.c | 19 ++++++---- fs/ext4/snapshot_ctl.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++-- 3 files changed, 118 insertions(+), 11 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 34aaade..6f0f310 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1737,6 +1737,12 @@ struct ext4_features { struct completion f_kobj_unregister; }; +typedef struct { + __le32 *p; + __le32 key; + struct buffer_head *bh; +} Indirect; + /* * Function prototypes */ @@ -1878,6 +1884,16 @@ extern void ext4_da_update_reserve_space(struct inode *inode, /* snapshot_inode.c */ extern int ext4_snapshot_readpage(struct file *file, struct page *page); +extern int ext4_block_to_path(struct inode *inode, + ext4_lblk_t i_block, + ext4_lblk_t offsets[4], int *boundary); +extern Indirect *ext4_get_branch(struct inode *inode, int depth, + ext4_lblk_t *offsets, + Indirect chain[4], int *err); +extern void ext4_free_branches(handle_t *handle, struct inode *inode, + struct buffer_head *parent_bh, + __le32 *first, __le32 *last, + int depth); /* ioctl.c */ extern long ext4_ioctl(struct file *, unsigned int, unsigned long); extern long ext4_compat_ioctl(struct file *, unsigned int, unsigned long); diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 89a97da..5199035 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -176,6 +176,14 @@ int ext4_truncate_restart_trans(handle_t *handle, struct inode *inode, */ BUG_ON(EXT4_JOURNAL(inode) == NULL); jbd_debug(2, "restarting handle %p\n", handle); + /* + * Snapshot shrink/merge/clean do not take i_data_sem, so we cannot + * release it here. Luckily, snapshot files are not writable, + * so deadlock with ext4_map_blocks on writepage is impossible. + * Snapshot files also don't have preallocations. + */ + if (ext4_snapshot_file(inode)) + return ext4_journal_restart(handle, nblocks); up_write(&EXT4_I(inode)->i_data_sem); ret = ext4_journal_restart(handle, nblocks); down_write(&EXT4_I(inode)->i_data_sem); @@ -281,11 +289,6 @@ no_delete: ext4_clear_inode(inode); /* We must guarantee clearing of inode... */ } -typedef struct { - __le32 *p; - __le32 key; - struct buffer_head *bh; -} Indirect; static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v) { @@ -324,7 +327,7 @@ static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v) * get there at all. */ -static int ext4_block_to_path(struct inode *inode, +int ext4_block_to_path(struct inode *inode, ext4_lblk_t i_block, ext4_lblk_t offsets[4], int *boundary) { @@ -440,7 +443,7 @@ static int __ext4_check_blockref(const char *function, unsigned int line, * Need to be called with * down_read(&EXT4_I(inode)->i_data_sem) */ -static Indirect *ext4_get_branch(struct inode *inode, int depth, +Indirect *ext4_get_branch(struct inode *inode, int depth, ext4_lblk_t *offsets, Indirect chain[4], int *err) { @@ -4679,7 +4682,7 @@ static void ext4_free_data(handle_t *handle, struct inode *inode, * stored as little-endian 32-bit) and updating @inode->i_blocks * appropriately. */ -static void ext4_free_branches(handle_t *handle, struct inode *inode, +void ext4_free_branches(handle_t *handle, struct inode *inode, struct buffer_head *parent_bh, __le32 *first, __le32 *last, int depth) { diff --git a/fs/ext4/snapshot_ctl.c b/fs/ext4/snapshot_ctl.c index 9e39c04..13048f5 100644 --- a/fs/ext4/snapshot_ctl.c +++ b/fs/ext4/snapshot_ctl.c @@ -1149,6 +1149,53 @@ out_err: } /* + * ext4_snapshot_clean() frees snapshot file blocks + * before removing snapshot file from snapshots list. + * Called from ext4_snapshot_remove() under snapshot_mutex. + * + * Returns 0 on success and < 0 on error. + */ +static int ext4_snapshot_clean(handle_t *handle, struct inode *inode) +{ + struct ext4_inode_info *ei = EXT4_I(inode); + int i; + + if (!ext4_snapshot_list(inode)) { + snapshot_debug(1, "ext4_snapshot_clean() called with " + "snapshot file (ino=%lu) not on list\n", + inode->i_ino); + return -EINVAL; + } + + if (ext4_test_inode_snapstate(inode, EXT4_SNAPSTATE_ACTIVE)) { + snapshot_debug(1, "clean of active snapshot (%u) " + "is not allowed.\n", + inode->i_generation); + return -EPERM; + } + + /* + * A very simplified version of ext4_truncate() for snapshot files. + * A non-active snapshot file never allocates new blocks and only frees + * blocks under snapshot_mutex, so no need to take truncate_mutex here. + * No need to add inode to orphan list for post crash truncate, because + * snapshot is still on the snapshot list and marked for deletion. + * Free DIND branch last, to keep snapshot's super block around longer. + */ + for (i = EXT4_SNAPSHOT_N_BLOCKS - 1; i >= EXT4_DIND_BLOCK; i--) { + int depth = (i == EXT4_DIND_BLOCK ? 2 : 3); + int j = i%EXT4_N_BLOCKS; + + if (!ei->i_data[j]) + continue; + ext4_free_branches(handle, inode, NULL, + ei->i_data+j, ei->i_data+j+1, depth); + ei->i_data[j] = 0; + } + return 0; +} + +/* * ext4_snapshot_enable() enables snapshot mount * sets the in-use flag and the active snapshot * Called under i_mutex and snapshot_mutex @@ -1277,6 +1324,17 @@ static int ext4_snapshot_remove(struct inode *inode) } sbi = EXT4_SB(inode->i_sb); + /* free snapshot inode blocks */ + err = ext4_snapshot_clean(handle, inode); + if (err) + goto out_handle; + + /* reset i_size and i_disksize and invalidate page cache */ + SNAPSHOT_SET_REMOVED(inode); + + err = ext4_mark_inode_dirty(handle, inode); + if (err) + goto out_handle; err = extend_or_restart_transaction_inode(handle, inode, 2); if (err) @@ -1321,6 +1379,34 @@ out_err: } /* + * ext4_snapshot_cleanup - shrink/merge/remove snapshot marked for deletion + * @inode - inode in question + * @used_by - latest non-deleted snapshot + * @deleted - true if snapshot is marked for deletion and not active + * @need_shrink - counter of deleted snapshots to shrink + * @need_merge - counter of deleted snapshots to merge + * + * Deleted snapshot with no older non-deleted snapshot - remove from list + * Deleted snapshot with no older enabled snapshot - add to merge count + * Deleted snapshot with older enabled snapshot - add to shrink count + * Non-deleted snapshot - shrink and merge deleted snapshots group + * + * Called from ext4_snapshot_update() under snapshot_mutex. + * Returns 0 on success and <0 on error. + */ +static int ext4_snapshot_cleanup(struct inode *inode, struct inode *used_by, + int deleted, int *need_shrink, int *need_merge) +{ + int err = 0; + + if (deleted && !used_by) + /* remove permanently unused deleted snapshot */ + return ext4_snapshot_remove(inode); + + return 0; +} + +/* * Snapshot constructor/destructor */ /* @@ -1462,6 +1548,8 @@ int ext4_snapshot_update(struct super_block *sb, int cleanup, int read_only) int found_active = 0; int found_enabled = 0; struct list_head *prev; + int need_shrink = 0; + int need_merge = 0; int err = 0; BUG_ON(read_only && cleanup); @@ -1521,9 +1609,9 @@ update_snapshot: /* snapshot is not in use by older enabled snapshots */ ext4_clear_inode_snapstate(inode, EXT4_SNAPSTATE_INUSE); - if (cleanup && deleted && !used_by) - /* remove permanently unused deleted snapshot */ - err = ext4_snapshot_remove(inode); + if (cleanup) + err = ext4_snapshot_cleanup(inode, used_by, deleted, + &need_shrink, &need_merge); if (!deleted) { if (!found_active) -- 1.7.4.1