From: Goldwyn Rodrigues <rgold...@suse.com> 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 <rgold...@suse.com> --- fs/ext4/file.c | 48 +++++++++++++++++++++++++++++++----------------- 1 file changed, 31 insertions(+), 17 deletions(-) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index 8210c1f..e223b9f 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -127,27 +127,22 @@ ext4_unaligned_aio(struct inode *inode, struct iov_iter *from, loff_t pos) return 0; } -/* Is IO overwriting allocated and initialized blocks? */ -static bool ext4_overwrite_io(struct inode *inode, loff_t pos, loff_t len) +/* Are IO blocks allocated */ +static bool ext4_blocks_mapped(struct inode *inode, loff_t pos, loff_t len, + struct ext4_map_blocks *map) { - struct ext4_map_blocks map; unsigned int blkbits = inode->i_blkbits; int err, blklen; if (pos + len > i_size_read(inode)) return false; - map.m_lblk = pos >> blkbits; - map.m_len = EXT4_MAX_BLOCKS(len, pos, blkbits); - blklen = map.m_len; + map->m_lblk = pos >> blkbits; + map->m_len = EXT4_MAX_BLOCKS(len, pos, blkbits); + blklen = map->m_len; - err = ext4_map_blocks(NULL, inode, &map, 0); - /* - * 'err==len' means that all of the blocks have been preallocated, - * regardless of whether they have been initialized or not. To exclude - * unwritten extents, we need to check m_flags. - */ - return err == blklen && (map.m_flags & EXT4_MAP_MAPPED); + err = ext4_map_blocks(NULL, inode, map, 0); + return err == blklen; } static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from) @@ -204,6 +199,7 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from) { struct inode *inode = file_inode(iocb->ki_filp); int o_direct = iocb->ki_flags & IOCB_DIRECT; + int nowait = iocb->ki_flags & IOCB_NOWAIT; int unaligned_aio = 0; int overwrite = 0; ssize_t ret; @@ -216,7 +212,13 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from) return ext4_dax_write_iter(iocb, from); #endif - inode_lock(inode); + if (o_direct && nowait) { + if (!inode_trylock(inode)) + return -EAGAIN; + } else { + inode_lock(inode); + } + ret = ext4_write_checks(iocb, from); if (ret <= 0) goto out; @@ -235,9 +237,21 @@ 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) { + struct ext4_map_blocks map; + if (ext4_blocks_mapped(inode, iocb->ki_pos, + iov_iter_count(from), &map)) { + /* To exclude unwritten extents, we need to check + * m_flags. + */ + if (ext4_should_dioread_nolock(inode) && + (map.m_flags & EXT4_MAP_MAPPED)) + overwrite = 1; + } else if (iocb->ki_flags & IOCB_NOWAIT) { + ret = -EAGAIN; + goto out; + } + } ret = __generic_file_write_iter(iocb, from); inode_unlock(inode); -- 2.10.2