From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
Return EAGAIN if any of the following checks fail
+ i_rwsem is not lockable
+ NODATACOW or PREALLOC is not set
+ Cannot nocow at the desired location
+ Writing beyond end of file which is not allocated
---
fs/btrfs/file.c | 25 ++++++++++++++++++++-----
fs/btrfs/inode.c | 3 +++
fs/btrfs/super.c | 2 +-
3 files changed, 24 insertions(+), 6 deletions(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 520cb72..a870e5d 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1823,12 +1823,29 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
ssize_t num_written = 0;
bool sync = (file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host);
ssize_t err;
- loff_t pos;
- size_t count;
+ loff_t pos = iocb->ki_pos;
+ size_t count = iov_iter_count(from);
loff_t oldsize;
int clean_page = 0;
- inode_lock(inode);
+ if ((iocb->ki_flags & IOCB_NOWAIT) &&
+ (iocb->ki_flags & IOCB_DIRECT)) {
+ /* Don't sleep on inode rwsem */
+ if (!inode_trylock(inode))
+ return -EAGAIN;
+ /*
+ * We will allocate space in case nodatacow is not set,
+ * so bail
+ */
+ if (!(BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
+ BTRFS_INODE_PREALLOC)) ||
+ check_can_nocow(BTRFS_I(inode), pos, &count) <= 0) {
+ inode_unlock(inode);
+ return -EAGAIN;
+ }
+ } else
+ inode_lock(inode);
+
err = generic_write_checks(iocb, from);
if (err <= 0) {
inode_unlock(inode);
@@ -1862,8 +1879,6 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
*/
update_time_for_write(inode);
- pos = iocb->ki_pos;
- count = iov_iter_count(from);
start_pos = round_down(pos, fs_info->sectorsize);
oldsize = i_size_read(inode);
if (start_pos > oldsize) {
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a18510b..d91b21a 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8627,6 +8627,9 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
dio_data.overwrite = 1;
inode_unlock(inode);
relock = true;
+ } else if (iocb->ki_flags & IOCB_NOWAIT) {
+ ret = -EAGAIN;
+ goto out;
}
ret = btrfs_delalloc_reserve_space(inode, offset, count);
if (ret)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index da687dc..5e60659 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2175,7 +2175,7 @@ static struct file_system_type btrfs_fs_type = {
.name = "btrfs",
.mount = btrfs_mount,
.kill_sb = btrfs_kill_super,
- .fs_flags = FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA,
+ .fs_flags = FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA | FS_NOWAIT,
};
MODULE_ALIAS_FS("btrfs");
--
2.10.2
