> On Feb 13, 2017, at 7:46 PM, Goldwyn Rodrigues <rgoldwyn@xxxxxxx> wrote:
>
> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>
> 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 allocated at the write location
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> ---
> fs/ext4/file.c | 28 ++++++++++++++++++++++------
> 1 file changed, 22 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 2a822d3..c8d1e41 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -93,11 +93,16 @@ 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 nonblocking = iocb->ki_flags & IOCB_NONBLOCKING;
> int unaligned_aio = 0;
> int overwrite = 0;
> ssize_t ret;
>
> - inode_lock(inode);
> + if (o_direct && nonblocking) {
> + if (!inode_trylock(inode))
> + return -EAGAIN;
Why do these all return -EAGAIN instead of -EWOULDBLOCK? -EAGAIN is already
used in a number of places, and -EWOULDBLOCK seems more correct in the
"nonblocking" case?
> + } else
> + inode_lock(inode);
(style) "else" blocks should have braces when the "if" block has braces
> ret = generic_write_checks(iocb, from);
> if (ret <= 0)
> goto out;
> @@ -132,12 +137,18 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> if (o_direct) {
> size_t length = iov_iter_count(from);
> loff_t pos = iocb->ki_pos;
> + unsigned int blkbits = inode->i_blkbits;
> +
> + if (nonblocking
> + && (pos + length > EXT4_BLOCK_ALIGN(i_size_read(inode), blkbits))) {
(style) "&&" should go at the end of the previous line
(style) continued lines should align after '(' on previous line
(style) no need for parenthesis around that comparison
> + ret = -EAGAIN;
> + goto out;
> + }
>
> /* check whether we do a DIO overwrite or not */
> - if (ext4_should_dioread_nolock(inode) && !unaligned_aio &&
> - pos + length <= i_size_read(inode)) {
> + if ((ext4_should_dioread_nolock(inode) && !unaligned_aio &&
> + pos + length <= i_size_read(inode)) || nonblocking) {
(style) continued line should align after second '(' of previous line
> struct ext4_map_blocks map;
> - unsigned int blkbits = inode->i_blkbits;
> int err, len;
>
> map.m_lblk = pos >> blkbits;
> @@ -157,8 +168,13 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> * non-flags are returned. So we should check
> * these two conditions.
> */
> - if (err == len && (map.m_flags & EXT4_MAP_MAPPED))
> - overwrite = 1;
> + if (err == len) {
> + if (map.m_flags & EXT4_MAP_MAPPED)
> + overwrite = 1;
> + } else if (nonblocking) {
> + ret = -EAGAIN;
> + goto out;
> + }
> }
> }
>
> --
> 2.10.2
>
Cheers, Andreas
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