[PATCH 4/5] btrfs: add nowait parameter to btrfs_encoded_read

Mark Harmstone
2024-10-14T17:18:52Z

Adds a nowait parameter to btrfs_encoded_read, which if it is true
causes the function to return -EAGAIN rather than sleeping.

Signed-off-by: Mark Harmstone <maharmstone@fb.com>
---
fs/btrfs/btrfs_inode.h | 2 +-
fs/btrfs/inode.c | 59 ++++++++++++++++++++++++++++++++----------
fs/btrfs/ioctl.c | 2 +-
3 files changed, 47 insertions(+), 16 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 3a0b519c51ca..2334961e71ed 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -618,7 +618,7 @@ int btrfs_encoded_read_regular_fill_pages(struct btrfs_inode *inode,
void *cb_ctx);
ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
struct btrfs_ioctl_encoded_io_args *encoded,
- struct extent_state **cached_state,
+ bool nowait, struct extent_state **cached_state,
u64 *disk_bytenr, u64 *disk_io_size);
ssize_t btrfs_encoded_read_regular(struct kiocb *iocb, struct iov_iter *iter,
u64 start, u64 lockend,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index e58284d33b35..c536e37cb6b6 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8999,7 +8999,7 @@ static ssize_t btrfs_encoded_read_inline(
struct extent_state **cached_state,
u64 extent_start, size_t count,
struct btrfs_ioctl_encoded_io_args *encoded,
- bool *unlocked)
+ bool *unlocked, bool nowait)
{
struct btrfs_inode *inode = BTRFS_I(file_inode(iocb->ki_filp));
struct btrfs_root *root = inode->root;
@@ -9018,6 +9018,9 @@ static ssize_t btrfs_encoded_read_inline(
ret = -ENOMEM;
goto out;
}
+
+ path->nowait = !!nowait;
+
ret = btrfs_lookup_file_extent(NULL, root, path, btrfs_ino(inode),
extent_start, 0);
if (ret) {
@@ -9254,7 +9257,7 @@ ssize_t btrfs_encoded_read_regular(struct kiocb *iocb, struct iov_iter *iter,

ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
struct btrfs_ioctl_encoded_io_args *encoded,
- struct extent_state **cached_state,
+ bool nowait, struct extent_state **cached_state,
u64 *disk_bytenr, u64 *disk_io_size)
{
struct btrfs_inode *inode = BTRFS_I(file_inode(iocb->ki_filp));
@@ -9268,7 +9271,10 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,

file_accessed(iocb->ki_filp);

- btrfs_inode_lock(inode, BTRFS_ILOCK_SHARED);
+ ret = btrfs_inode_lock(inode,
+ BTRFS_ILOCK_SHARED | (nowait ? BTRFS_ILOCK_TRY : 0));
+ if (ret)
+ return ret;

if (iocb->ki_pos >= inode->vfs_inode.i_size) {
btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
@@ -9281,21 +9287,45 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
*/
lockend = start + BTRFS_MAX_UNCOMPRESSED - 1;

- for (;;) {
+ if (nowait) {
struct btrfs_ordered_extent *ordered;

- ret = btrfs_wait_ordered_range(inode, start,
- lockend - start + 1);
- if (ret)
+ if (filemap_range_needs_writeback(inode->vfs_inode.i_mapping,
+ start, lockend)) {
+ ret = -EAGAIN;
goto out_unlock_inode;
- lock_extent(io_tree, start, lockend, cached_state);
+ }
+
+ if (!try_lock_extent(io_tree, start, lockend, cached_state)) {
+ ret = -EAGAIN;
+ goto out_unlock_inode;
+ }
+
ordered = btrfs_lookup_ordered_range(inode, start,
lockend - start + 1);
- if (!ordered)
- break;
- btrfs_put_ordered_extent(ordered);
- unlock_extent(io_tree, start, lockend, cached_state);
- cond_resched();
+ if (ordered) {
+ btrfs_put_ordered_extent(ordered);
+ unlock_extent(io_tree, start, lockend, cached_state);
+ ret = -EAGAIN;
+ goto out_unlock_inode;
+ }
+ } else {
+ for (;;) {
+ struct btrfs_ordered_extent *ordered;
+
+ ret = btrfs_wait_ordered_range(inode, start,
+ lockend - start + 1);
+ if (ret)
+ goto out_unlock_inode;
+ lock_extent(io_tree, start, lockend, cached_state);
+ ordered = btrfs_lookup_ordered_range(inode, start,
+ lockend - start + 1);
+ if (!ordered)
+ break;
+ btrfs_put_ordered_extent(ordered);
+ unlock_extent(io_tree, start, lockend, cached_state);
+ cond_resched();
+ }
}

em = btrfs_get_extent(inode, NULL, start, lockend - start + 1);
@@ -9315,7 +9345,8 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
em = NULL;
ret = btrfs_encoded_read_inline(iocb, iter, start, lockend,
cached_state, extent_start,
- count, encoded, &unlocked);
+ count, encoded, &unlocked,
+ nowait);
goto out_em;
}

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index e2ecf0bcda24..8c9ff4898ab0 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4579,7 +4579,7 @@ static int btrfs_ioctl_encoded_read(struct file *file, void __user *argp,
init_sync_kiocb(&kiocb, file);
kiocb.ki_pos = pos;

- ret = btrfs_encoded_read(&kiocb, &iter, &args, &cached_state,
+ ret = btrfs_encoded_read(&kiocb, &iter, &args, false, &cached_state,
&disk_bytenr, &disk_io_size);

if (ret == -EIOCBQUEUED) {
--
2.44.2