ext4: nowait aio support

Return EAGAIN if any of the following checks fail for direct I/O:
  + i_rwsem is lockable
  + Writing beyond end of file (will trigger allocation)
  + Blocks are not allocated at the write location

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 02ce7e7bbdf5ba4da0db50e50d8d4cab49cde4a3..58e2eeaa0bc49134ad86eabef47d53ab6b019705 100644 (file)
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -37,7 +37,11 @@ static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
        struct inode *inode = file_inode(iocb->ki_filp);
        ssize_t ret;
 
-       inode_lock_shared(inode);
+       if (!inode_trylock_shared(inode)) {
+               if (iocb->ki_flags & IOCB_NOWAIT)
+                       return -EAGAIN;
+               inode_lock_shared(inode);
+       }
        /*
         * Recheck under inode lock - at this point we are sure it cannot
         * change anymore
@@ -179,7 +183,11 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
        struct inode *inode = file_inode(iocb->ki_filp);
        ssize_t ret;
 
-       inode_lock(inode);
+       if (!inode_trylock(inode)) {
+               if (iocb->ki_flags & IOCB_NOWAIT)
+                       return -EAGAIN;
+               inode_lock(inode);
+       }
        ret = ext4_write_checks(iocb, from);
        if (ret <= 0)
                goto out;
@@ -216,7 +224,12 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
                return ext4_dax_write_iter(iocb, from);
 #endif
 
-       inode_lock(inode);
+       if (!inode_trylock(inode)) {
+               if (iocb->ki_flags & IOCB_NOWAIT)
+                       return -EAGAIN;
+               inode_lock(inode);
+       }
+
        ret = ext4_write_checks(iocb, from);
        if (ret <= 0)
                goto out;
@@ -235,9 +248,15 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 
        iocb->private = &overwrite;
        /* Check whether we do a DIO overwrite or not */
-       if (o_direct && ext4_should_dioread_nolock(inode) && !unaligned_aio &&
-           ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from)))
-               overwrite = 1;
+       if (o_direct && !unaligned_aio) {
+               if (ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from))) {
+                       if (ext4_should_dioread_nolock(inode))
+                               overwrite = 1;
+               } else if (iocb->ki_flags & IOCB_NOWAIT) {
+                       ret = -EAGAIN;
+                       goto out;
+               }
+       }
 
        ret = __generic_file_write_iter(iocb, from);
        inode_unlock(inode);
@@ -435,6 +454,10 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
                if (ret < 0)
                        return ret;
        }
+
+       /* Set the flags to support nowait AIO */
+       filp->f_mode |= FMODE_AIO_NOWAIT;
+
        return dquot_file_open(inode, filp);
 }