diff options
| author | Goldwyn Rodrigues <rgoldwyn@suse.com> | 2017-06-20 07:05:44 -0500 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-06-20 07:12:03 -0600 |
| commit | 6be96d3ad34a124450028dabba43f07fe1d0c86d (patch) | |
| tree | a5f6ef95a01e38caa3dc1e50071d5baa78426a3f /mm/filemap.c | |
| parent | b745fafaf70c0a98a2e1e7ac8cb14542889ceb0e (diff) | |
| download | lwn-6be96d3ad34a124450028dabba43f07fe1d0c86d.tar.gz lwn-6be96d3ad34a124450028dabba43f07fe1d0c86d.zip | |
fs: return if direct I/O will trigger writeback
Find out if the I/O will trigger a wait due to writeback. If yes,
return -EAGAIN.
Return -EINVAL for buffered AIO: there are multiple causes of
delay such as page locks, dirty throttling logic, page loading
from disk etc. which cannot be taken care of.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'mm/filemap.c')
| -rw-r--r-- | mm/filemap.c | 32 |
1 files changed, 25 insertions, 7 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index 9b39a2390b9e..742034e56100 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2070,10 +2070,17 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) loff_t size; size = i_size_read(inode); - retval = filemap_write_and_wait_range(mapping, iocb->ki_pos, - iocb->ki_pos + count - 1); - if (retval < 0) - goto out; + if (iocb->ki_flags & IOCB_NOWAIT) { + if (filemap_range_has_page(mapping, iocb->ki_pos, + iocb->ki_pos + count - 1)) + return -EAGAIN; + } else { + retval = filemap_write_and_wait_range(mapping, + iocb->ki_pos, + iocb->ki_pos + count - 1); + if (retval < 0) + goto out; + } file_accessed(file); @@ -2674,6 +2681,9 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) pos = iocb->ki_pos; + if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT)) + return -EINVAL; + if (limit != RLIM_INFINITY) { if (iocb->ki_pos >= limit) { send_sig(SIGXFSZ, current, 0); @@ -2742,9 +2752,17 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from) write_len = iov_iter_count(from); end = (pos + write_len - 1) >> PAGE_SHIFT; - written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); - if (written) - goto out; + if (iocb->ki_flags & IOCB_NOWAIT) { + /* If there are pages to writeback, return */ + if (filemap_range_has_page(inode->i_mapping, pos, + pos + iov_iter_count(from))) + return -EAGAIN; + } else { + written = filemap_write_and_wait_range(mapping, pos, + pos + write_len - 1); + if (written) + goto out; + } /* * After a write we want buffered reads to be sure to go to disk to get |