btrfs: nowait aio support

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

Acked-by: David Sterba <dsterba@suse.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index da1096e..59e2dcc 100644 (file)
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1875,12 +1875,29 @@ 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);
@@ -1914,8 +1931,6 @@ 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) {
@@ -3071,13 +3086,19 @@ out:
        return offset;
 }
 
+static int btrfs_file_open(struct inode *inode, struct file *filp)
+{
+       filp->f_mode |= FMODE_AIO_NOWAIT;
+       return generic_file_open(inode, filp);
+}
+
 const struct file_operations btrfs_file_operations = {
        .llseek         = btrfs_file_llseek,
        .read_iter      = generic_file_read_iter,
        .splice_read    = generic_file_splice_read,
        .write_iter     = btrfs_file_write_iter,
        .mmap           = btrfs_file_mmap,
-       .open           = generic_file_open,
+       .open           = btrfs_file_open,
        .release        = btrfs_release_file,
        .fsync          = btrfs_sync_file,
        .fallocate      = btrfs_fallocate,

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f942293..556c930 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8754,6 +8754,9 @@ 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)