From: Amir Goldstein <amir73il@xxxxxxxxxxxx>
Files larger than 2TB use Ext4 huge_file flag to store i_blocks
in file system blocks units, so the upper limit on snapshot actual
size is increased from 512*2^32 = 2TB to 4K*2^32 = 16TB,
which is also the upper limit on file system size.
To map 2^32 logical blocks, 4 triple indirect blocks are used instead
of just one. The extra 3 triple indirect blocks are stored in-place
of direct blocks, which are not in use by snapshot files.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxxxxx>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@xxxxxxxxx>
---
fs/ext4/ext4.h | 13 +++++++++++++
fs/ext4/inode.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
fs/ext4/super.c | 5 ++++-
3 files changed, 59 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 4072036..8f59322 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -333,6 +333,19 @@ struct flex_groups {
#define EXT4_DIND_BLOCK (EXT4_IND_BLOCK + 1)
#define EXT4_TIND_BLOCK (EXT4_DIND_BLOCK + 1)
#define EXT4_N_BLOCKS (EXT4_TIND_BLOCK + 1)
+/*
+ * Snapshot files have different indirection mapping that can map up to 2^32
+ * logical blocks, so they can cover the mapped filesystem block address space.
+ * Ext4 must use either 4K or 8K blocks (depending on PAGE_SIZE).
+ * With 8K blocks, 1 triple indirect block maps 2^33 logical blocks.
+ * With 4K blocks (the system default), each triple indirect block maps 2^30
+ * logical blocks, so 4 triple indirect blocks map 2^32 logical blocks.
+ * Snapshot files in small filesystems (<= 4G), use only 1 double indirect
+ * block to map the entire filesystem.
+ */
+#define EXT4_SNAPSHOT_EXTRA_TIND_BLOCKS 3
+#define EXT4_SNAPSHOT_N_BLOCKS (EXT4_TIND_BLOCK + 1 + \
+ EXT4_SNAPSHOT_EXTRA_TIND_BLOCKS)
/*
* Inode flags
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index db1706f..425dabb 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -335,6 +335,7 @@ static int ext4_block_to_path(struct inode *inode,
double_blocks = (1 << (ptrs_bits * 2));
int n = 0;
int final = 0;
+ int tind;
if (i_block < direct_blocks) {
offsets[n++] = i_block;
@@ -354,6 +355,18 @@ static int ext4_block_to_path(struct inode *inode,
offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
offsets[n++] = i_block & (ptrs - 1);
final = ptrs;
+ } else if (ext4_snapshot_file(inode) &&
+ (i_block >> (ptrs_bits * 3)) <
+ EXT4_SNAPSHOT_EXTRA_TIND_BLOCKS + 1) {
+ tind = i_block >> (ptrs_bits * 3);
+ BUG_ON(tind == 0);
+ /* use up to 4 triple indirect blocks to map 2^32 blocks */
+ i_block -= (tind << (ptrs_bits * 3));
+ offsets[n++] = (EXT4_TIND_BLOCK + tind) % EXT4_NDIR_BLOCKS;
+ offsets[n++] = i_block >> (ptrs_bits * 2);
+ offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
+ offsets[n++] = i_block & (ptrs - 1);
+ final = ptrs;
} else {
ext4_warning(inode->i_sb, "block %lu > max in inode %lu",
i_block + direct_blocks +
@@ -4748,6 +4761,13 @@ void ext4_truncate(struct inode *inode)
ext4_lblk_t last_block, max_block;
unsigned blocksize = inode->i_sb->s_blocksize;
+ /* prevent partial truncate of snapshot files */
+ if (ext4_snapshot_file(inode) && inode->i_size != 0) {
+ snapshot_debug(1, "snapshot file (%lu) cannot be partly "
+ "truncated!\n", inode->i_ino);
+ return;
+ }
+
/* prevent truncate of files on snapshot list */
if (ext4_snapshot_list(inode)) {
snapshot_debug(1, "snapshot (%u) cannot be truncated!\n",
@@ -4861,6 +4881,10 @@ do_indirects:
/* Kill the remaining (whole) subtrees */
switch (offsets[0]) {
default:
+ if (ext4_snapshot_file(inode) &&
+ offsets[0] < EXT4_SNAPSHOT_EXTRA_TIND_BLOCKS)
+ /* Freeing snapshot extra tind branches */
+ break;
nr = i_data[EXT4_IND_BLOCK];
if (nr) {
ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
@@ -4882,6 +4906,19 @@ do_indirects:
;
}
+ if (ext4_snapshot_file(inode)) {
+ int i;
+
+ /* Kill the remaining snapshot file triple indirect trees */
+ for (i = 0; i < EXT4_SNAPSHOT_EXTRA_TIND_BLOCKS; i++) {
+ nr = i_data[i];
+ if (!nr)
+ continue;
+ ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
+ i_data[i] = 0;
+ }
+ }
+
out_unlock:
up_write(&ei->i_data_sem);
inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
@@ -5114,7 +5151,8 @@ static blkcnt_t ext4_inode_blocks(struct ext4_inode *raw_inode,
struct super_block *sb = inode->i_sb;
if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
- EXT4_FEATURE_RO_COMPAT_HUGE_FILE)) {
+ EXT4_FEATURE_RO_COMPAT_HUGE_FILE) ||
+ ext4_snapshot_file(inode)) {
/* we are using combined 48 bit field */
i_blocks = ((u64)le16_to_cpu(raw_inode->i_blocks_high)) << 32 |
le32_to_cpu(raw_inode->i_blocks_lo);
@@ -5353,7 +5391,9 @@ static int ext4_inode_blocks_set(handle_t *handle,
ext4_clear_inode_flag(inode, EXT4_INODE_HUGE_FILE);
return 0;
}
- if (!EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_HUGE_FILE))
+ /* snapshot files may be represented as huge files */
+ if (!EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_HUGE_FILE) &&
+ !ext4_snapshot_file(inode))
return -EFBIG;
if (i_blocks <= 0xffffffffffffULL) {
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e3ebd7d..d26831a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2316,7 +2316,7 @@ static loff_t ext4_max_bitmap_size(int bits, int has_huge_files)
res += 1LL << (bits-2);
res += 1LL << (2*(bits-2));
- res += 1LL << (3*(bits-2));
+ res += (1LL + EXT4_SNAPSHOT_EXTRA_TIND_BLOCKS) << (3*(bits-2));
res <<= bits;
if (res > upper_limit)
res = upper_limit;
@@ -3259,6 +3259,9 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
has_huge_files = EXT4_HAS_RO_COMPAT_FEATURE(sb,
EXT4_FEATURE_RO_COMPAT_HUGE_FILE);
+ if (EXT4_SNAPSHOTS(sb))
+ /* Snapshot files are huge files */
+ has_huge_files = 1;
sbi->s_bitmap_maxbytes = ext4_max_bitmap_size(sb->s_blocksize_bits,
has_huge_files);
sb->s_maxbytes = ext4_max_size(sb->s_blocksize_bits, has_huge_files);
--
1.7.0.4
--
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