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Commit 8b9433eb authored by Ernesto A. Fernández's avatar Ernesto A. Fernández Committed by Jens Axboe
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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: default avatarJeff Moyer <jmoyer@redhat.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarErnesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Signed-off-by: default avatarJens 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;

		}