On 02/14/2017 01:52 PM, Andreas Dilger wrote:
>
>> 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?
It is the same :)
#define EWOULDBLOCK EAGAIN /* Operation would block */
I didn’t know before I started this work either.
Anyways, I based this on 4.9.9 but there are changes in ext4 code in
4.10-rcx so I need to redo the patches. Thanks for the style reviews.
>
>> + } 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
>
>
>
>
>
--
Goldwyn
