Commit 8b9433eb authored Oct 08, 2018 by Ernesto A. Fernández Committed by Jens Axboe Jan 22, 2019

direct-io: allow direct writes to empty inodes



On a DIO_SKIP_HOLES filesystem, the ->get_block() method is currently
not allowed to create blocks for an empty inode.  This confusion comes
from trying to bit shift a negative number, so check the size of the
inode first.

The problem is most visible for hfsplus, because the fallback to
buffered I/O doesn't happen and the write fails with EIO.  This is in
part the fault of the module, because it gives a wrong return value on
->get_block(); that will be fixed in a separate patch.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 38197ca1

fs/direct-io.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -679,6 +679,7 @@ static int get_more_blocks(struct dio dio, struct dio_submit sdio,
		unsigned long fs_count; /* Number of filesystem-sized blocks */
		int create;
		unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
		loff_t i_size;

		/*
		* If there was a memory error and we've overwritten all the
		@@ -708,8 +709,8 @@ static int get_more_blocks(struct dio dio, struct dio_submit sdio,
		*/
		create = dio->op == REQ_OP_WRITE;
		if (dio->flags & DIO_SKIP_HOLES) {
		if (fs_startblk <= ((i_size_read(dio->inode) - 1) >>
		i_blkbits))
		i_size = i_size_read(dio->inode);
		if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits)
		create = 0;
		}

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