From: Amir Goldstein <amir73il@xxxxxxxxxxxx>
Core API of special snapshot file block operations.
The argument @create to the function ext4_getblk()
is re-interpreted as a snapshot block command argument. The old
argument values 0(=read) and 1(=create) preserve the original
behavior of the function. The bit field h_cowing in the current
transaction handle is used to prevent COW recursions.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxxxxx>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@xxxxxxxxx>
---
fs/ext4/ext4.h | 10 ++++++++++
fs/ext4/ext4_jbd2.h | 3 +++
fs/ext4/inode.c | 4 ++--
3 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 8f59322..c7fd33e 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -557,6 +557,16 @@ struct ext4_new_group_data {
* if EXT4_GET_BLOCKS_CREATE is not set, return REMAP flags.
*/
#define EXT4_GET_BLOCKS_MOVE_ON_WRITE 0x0100
+/*
+ * snapshot_map_blocks() flags passed to ext4_map_blocks() for mapping
+ * blocks to snapshot.
+ */
+ /* handle COW race conditions */
+#define EXT4_GET_BLOCKS_COW 0x200
+ /* allocate only indirect blocks */
+#define EXT4_GET_BLOCKS_MOVE 0x400
+ /* bypass journal and sync allocated indirect blocks directly to disk */
+#define EXT4_GET_BLOCKS_SYNC 0x800
/*
* Flags used by ext4_free_blocks
diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index e0fef0d..79b6594 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -173,6 +173,9 @@ int __ext4_handle_dirty_super(const char *where, unsigned int line,
#define ext4_handle_dirty_super(handle, sb) \
__ext4_handle_dirty_super(__func__, __LINE__, (handle), (sb))
+#define trace_cow_add(handle, name, num)
+#define trace_cow_inc(handle, name)
+
handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks);
int __ext4_journal_stop(const char *where, unsigned int line, handle_t *handle);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 425dabb..ba66545 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1600,8 +1600,8 @@ struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
map.m_lblk = block;
map.m_len = 1;
- err = ext4_map_blocks(handle, inode, &map,
- create ? EXT4_GET_BLOCKS_CREATE : 0);
+ /* passing SNAPMAP flags on create argument */
+ err = ext4_map_blocks(handle, inode, &map, create);
if (err < 0)
*errp = err;
--
1.7.0.4
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