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-rw-r--r--fs/btrfs/ctree.h1
-rw-r--r--fs/btrfs/disk-io.c1
-rw-r--r--fs/btrfs/inode.c25
-rw-r--r--fs/btrfs/ioctl.c16
4 files changed, 22 insertions, 21 deletions
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 318be7864072..a67cc190a84b 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1280,6 +1280,7 @@ struct btrfs_root {
int send_in_progress;
struct btrfs_subvolume_writers *subv_writers;
atomic_t will_be_snapshotted;
+ atomic_t snapshot_force_cow;
/* For qgroup metadata reserved space */
spinlock_t qgroup_meta_rsv_lock;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 5124c15705ce..05dc3c17cb62 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1187,6 +1187,7 @@ static void __setup_root(struct btrfs_root *root, struct btrfs_fs_info *fs_info,
atomic_set(&root->log_batch, 0);
refcount_set(&root->refs, 1);
atomic_set(&root->will_be_snapshotted, 0);
+ atomic_set(&root->snapshot_force_cow, 0);
root->log_transid = 0;
root->log_transid_committed = -1;
root->last_log_commit = 0;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3f51ddc18f98..c6d8c5d19ff0 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1271,7 +1271,7 @@ static noinline int run_delalloc_nocow(struct inode *inode,
u64 disk_num_bytes;
u64 ram_bytes;
int extent_type;
- int ret, err;
+ int ret;
int type;
int nocow;
int check_prev = 1;
@@ -1403,11 +1403,8 @@ next_slot:
* if there are pending snapshots for this root,
* we fall into common COW way.
*/
- if (!nolock) {
- err = btrfs_start_write_no_snapshotting(root);
- if (!err)
- goto out_check;
- }
+ if (!nolock && atomic_read(&root->snapshot_force_cow))
+ goto out_check;
/*
* force cow if csum exists in the range.
* this ensure that csum for a given extent are
@@ -1416,9 +1413,6 @@ next_slot:
ret = csum_exist_in_range(fs_info, disk_bytenr,
num_bytes);
if (ret) {
- if (!nolock)
- btrfs_end_write_no_snapshotting(root);
-
/*
* ret could be -EIO if the above fails to read
* metadata.
@@ -1431,11 +1425,8 @@ next_slot:
WARN_ON_ONCE(nolock);
goto out_check;
}
- if (!btrfs_inc_nocow_writers(fs_info, disk_bytenr)) {
- if (!nolock)
- btrfs_end_write_no_snapshotting(root);
+ if (!btrfs_inc_nocow_writers(fs_info, disk_bytenr))
goto out_check;
- }
nocow = 1;
} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
extent_end = found_key.offset +
@@ -1448,8 +1439,6 @@ next_slot:
out_check:
if (extent_end <= start) {
path->slots[0]++;
- if (!nolock && nocow)
- btrfs_end_write_no_snapshotting(root);
if (nocow)
btrfs_dec_nocow_writers(fs_info, disk_bytenr);
goto next_slot;
@@ -1471,8 +1460,6 @@ out_check:
end, page_started, nr_written, 1,
NULL);
if (ret) {
- if (!nolock && nocow)
- btrfs_end_write_no_snapshotting(root);
if (nocow)
btrfs_dec_nocow_writers(fs_info,
disk_bytenr);
@@ -1492,8 +1479,6 @@ out_check:
ram_bytes, BTRFS_COMPRESS_NONE,
BTRFS_ORDERED_PREALLOC);
if (IS_ERR(em)) {
- if (!nolock && nocow)
- btrfs_end_write_no_snapshotting(root);
if (nocow)
btrfs_dec_nocow_writers(fs_info,
disk_bytenr);
@@ -1532,8 +1517,6 @@ out_check:
EXTENT_CLEAR_DATA_RESV,
PAGE_UNLOCK | PAGE_SET_PRIVATE2);
- if (!nolock && nocow)
- btrfs_end_write_no_snapshotting(root);
cur_offset = extent_end;
/*
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index d3a5d2a41e5f..85c4284bb2cf 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -747,6 +747,7 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
struct btrfs_pending_snapshot *pending_snapshot;
struct btrfs_trans_handle *trans;
int ret;
+ bool snapshot_force_cow = false;
if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
return -EINVAL;
@@ -763,6 +764,11 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
goto free_pending;
}
+ /*
+ * Force new buffered writes to reserve space even when NOCOW is
+ * possible. This is to avoid later writeback (running dealloc) to
+ * fallback to COW mode and unexpectedly fail with ENOSPC.
+ */
atomic_inc(&root->will_be_snapshotted);
smp_mb__after_atomic();
/* wait for no snapshot writes */
@@ -773,6 +779,14 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
if (ret)
goto dec_and_free;
+ /*
+ * All previous writes have started writeback in NOCOW mode, so now
+ * we force future writes to fallback to COW mode during snapshot
+ * creation.
+ */
+ atomic_inc(&root->snapshot_force_cow);
+ snapshot_force_cow = true;
+
btrfs_wait_ordered_extents(root, U64_MAX, 0, (u64)-1);
btrfs_init_block_rsv(&pending_snapshot->block_rsv,
@@ -837,6 +851,8 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
fail:
btrfs_subvolume_release_metadata(fs_info, &pending_snapshot->block_rsv);
dec_and_free:
+ if (snapshot_force_cow)
+ atomic_dec(&root->snapshot_force_cow);
if (atomic_dec_and_test(&root->will_be_snapshotted))
wake_up_var(&root->will_be_snapshotted);
free_pending: