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Date: Tue, 7 Jun 2011 18:08:00 +0300
From: amir73il@...rs.sourceforge.net
To: linux-ext4@...r.kernel.org
Cc: tytso@....edu, lczerner@...hat.com,
Amir Goldstein <amir73il@...rs.sf.net>,
Yongqiang Yang <xiaoqiangnk@...il.com>
Subject: [PATCH v1 33/36] ext4: snapshot cleanup
From: Amir Goldstein <amir73il@...rs.sf.net>
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 <amir73il@...rs.sf.net>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
---
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
--
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