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-rw-r--r--fs/btrfs/ctree.h4
-rw-r--r--fs/btrfs/extent-tree.c16
-rw-r--r--fs/btrfs/file.c10
-rw-r--r--fs/btrfs/inode.c47
-rw-r--r--fs/btrfs/ioctl.c7
5 files changed, 60 insertions, 24 deletions
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 9918ba3ec2b2..fc73e86235e8 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3480,8 +3480,8 @@ int btrfs_init_space_info(struct btrfs_fs_info *fs_info);
int btrfs_delayed_refs_qgroup_accounting(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info);
int __get_raid_index(u64 flags);
-int btrfs_start_nocow_write(struct btrfs_root *root);
-void btrfs_end_nocow_write(struct btrfs_root *root);
+int btrfs_start_write_no_snapshoting(struct btrfs_root *root);
+void btrfs_end_write_no_snapshoting(struct btrfs_root *root);
/* ctree.c */
int btrfs_bin_search(struct extent_buffer *eb, struct btrfs_key *key,
int level, int *slot);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 5e81e3694d92..b4e3ab115f5f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -9656,12 +9656,14 @@ int btrfs_trim_fs(struct btrfs_root *root, struct fstrim_range *range)
}
/*
- * btrfs_{start,end}_write() is similar to mnt_{want, drop}_write(),
- * they are used to prevent the some tasks writing data into the page cache
- * by nocow before the subvolume is snapshoted, but flush the data into
- * the disk after the snapshot creation.
+ * btrfs_{start,end}_write_no_snapshoting() are similar to
+ * mnt_{want,drop}_write(), they are used to prevent some tasks from writing
+ * data into the page cache through nocow before the subvolume is snapshoted,
+ * but flush the data into disk after the snapshot creation, or to prevent
+ * operations while snapshoting is ongoing and that cause the snapshot to be
+ * inconsistent (writes followed by expanding truncates for example).
*/
-void btrfs_end_nocow_write(struct btrfs_root *root)
+void btrfs_end_write_no_snapshoting(struct btrfs_root *root)
{
percpu_counter_dec(&root->subv_writers->counter);
/*
@@ -9673,7 +9675,7 @@ void btrfs_end_nocow_write(struct btrfs_root *root)
wake_up(&root->subv_writers->wait);
}
-int btrfs_start_nocow_write(struct btrfs_root *root)
+int btrfs_start_write_no_snapshoting(struct btrfs_root *root)
{
if (atomic_read(&root->will_be_snapshoted))
return 0;
@@ -9684,7 +9686,7 @@ int btrfs_start_nocow_write(struct btrfs_root *root)
*/
smp_mb();
if (atomic_read(&root->will_be_snapshoted)) {
- btrfs_end_nocow_write(root);
+ btrfs_end_write_no_snapshoting(root);
return 0;
}
return 1;
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 0fbf0e7bc606..e4090259569b 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1428,7 +1428,7 @@ static noinline int check_can_nocow(struct inode *inode, loff_t pos,
u64 num_bytes;
int ret;
- ret = btrfs_start_nocow_write(root);
+ ret = btrfs_start_write_no_snapshoting(root);
if (!ret)
return -ENOSPC;
@@ -1451,7 +1451,7 @@ static noinline int check_can_nocow(struct inode *inode, loff_t pos,
ret = can_nocow_extent(inode, lockstart, &num_bytes, NULL, NULL, NULL);
if (ret <= 0) {
ret = 0;
- btrfs_end_nocow_write(root);
+ btrfs_end_write_no_snapshoting(root);
} else {
*write_bytes = min_t(size_t, *write_bytes ,
num_bytes - pos + lockstart);
@@ -1543,7 +1543,7 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
btrfs_free_reserved_data_space(inode,
reserve_bytes);
else
- btrfs_end_nocow_write(root);
+ btrfs_end_write_no_snapshoting(root);
break;
}
@@ -1632,7 +1632,7 @@ again:
release_bytes = 0;
if (only_release_metadata)
- btrfs_end_nocow_write(root);
+ btrfs_end_write_no_snapshoting(root);
if (only_release_metadata && copied > 0) {
u64 lockstart = round_down(pos, root->sectorsize);
@@ -1661,7 +1661,7 @@ again:
if (release_bytes) {
if (only_release_metadata) {
- btrfs_end_nocow_write(root);
+ btrfs_end_write_no_snapshoting(root);
btrfs_delalloc_release_metadata(inode, release_bytes);
} else {
btrfs_delalloc_release_space(inode, release_bytes);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a5374c2bb943..8de23355f6cf 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1337,7 +1337,7 @@ next_slot:
* we fall into common COW way.
*/
if (!nolock) {
- err = btrfs_start_nocow_write(root);
+ err = btrfs_start_write_no_snapshoting(root);
if (!err)
goto out_check;
}
@@ -1361,7 +1361,7 @@ out_check:
if (extent_end <= start) {
path->slots[0]++;
if (!nolock && nocow)
- btrfs_end_nocow_write(root);
+ btrfs_end_write_no_snapshoting(root);
goto next_slot;
}
if (!nocow) {
@@ -1381,7 +1381,7 @@ out_check:
page_started, nr_written, 1);
if (ret) {
if (!nolock && nocow)
- btrfs_end_nocow_write(root);
+ btrfs_end_write_no_snapshoting(root);
goto error;
}
cow_start = (u64)-1;
@@ -1432,7 +1432,7 @@ out_check:
num_bytes);
if (ret) {
if (!nolock && nocow)
- btrfs_end_nocow_write(root);
+ btrfs_end_write_no_snapshoting(root);
goto error;
}
}
@@ -1443,7 +1443,7 @@ out_check:
EXTENT_DELALLOC, PAGE_UNLOCK |
PAGE_SET_PRIVATE2);
if (!nolock && nocow)
- btrfs_end_nocow_write(root);
+ btrfs_end_write_no_snapshoting(root);
cur_offset = extent_end;
if (cur_offset > end)
break;
@@ -4599,6 +4599,26 @@ next:
return err;
}
+static int wait_snapshoting_atomic_t(atomic_t *a)
+{
+ schedule();
+ return 0;
+}
+
+static void wait_for_snapshot_creation(struct btrfs_root *root)
+{
+ while (true) {
+ int ret;
+
+ ret = btrfs_start_write_no_snapshoting(root);
+ if (ret)
+ break;
+ wait_on_atomic_t(&root->will_be_snapshoted,
+ wait_snapshoting_atomic_t,
+ TASK_UNINTERRUPTIBLE);
+ }
+}
+
static int btrfs_setsize(struct inode *inode, struct iattr *attr)
{
struct btrfs_root *root = BTRFS_I(inode)->root;
@@ -4623,17 +4643,30 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr)
if (newsize > oldsize) {
truncate_pagecache(inode, newsize);
+ /*
+ * Don't do an expanding truncate while snapshoting is ongoing.
+ * This is to ensure the snapshot captures a fully consistent
+ * state of this file - if the snapshot captures this expanding
+ * truncation, it must capture all writes that happened before
+ * this truncation.
+ */
+ wait_for_snapshot_creation(root);
ret = btrfs_cont_expand(inode, oldsize, newsize);
- if (ret)
+ if (ret) {
+ btrfs_end_write_no_snapshoting(root);
return ret;
+ }
trans = btrfs_start_transaction(root, 1);
- if (IS_ERR(trans))
+ if (IS_ERR(trans)) {
+ btrfs_end_write_no_snapshoting(root);
return PTR_ERR(trans);
+ }
i_size_write(inode, newsize);
btrfs_ordered_update_i_size(inode, i_size_read(inode), NULL);
ret = btrfs_update_inode(trans, root, inode);
+ btrfs_end_write_no_snapshoting(root);
btrfs_end_transaction(trans, root);
} else {
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 3abc068c5543..b590e23fa03e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -617,7 +617,7 @@ fail:
return ret;
}
-static void btrfs_wait_nocow_write(struct btrfs_root *root)
+static void btrfs_wait_for_no_snapshoting_writes(struct btrfs_root *root)
{
s64 writers;
DEFINE_WAIT(wait);
@@ -649,7 +649,7 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
atomic_inc(&root->will_be_snapshoted);
smp_mb__after_atomic();
- btrfs_wait_nocow_write(root);
+ btrfs_wait_for_no_snapshoting_writes(root);
ret = btrfs_start_delalloc_inodes(root, 0);
if (ret)
@@ -732,7 +732,8 @@ fail:
free:
kfree(pending_snapshot);
out:
- atomic_dec(&root->will_be_snapshoted);
+ if (atomic_dec_and_test(&root->will_be_snapshoted))
+ wake_up_atomic_t(&root->will_be_snapshoted);
return ret;
}
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.