From: Goldwyn Rodrigues <rgoldwyn@suse.de>
To: linux-fsdevel@vger.kernel.org
Cc: jack@suse.com, hch@infradead.org, linux-block@vger.kernel.org,
linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org,
linux-xfs@vger.kernel.org, sagi@grimberg.me, avi@scylladb.com,
axboe@kernel.dk, linux-api@vger.kernel.org, willy@infradead.org,
Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: [PATCH 3/8] nowait aio: return if direct write will trigger writeback
Date: Wed, 15 Mar 2017 16:51:02 -0500 [thread overview]
Message-ID: <20170315215107.5628-4-rgoldwyn@suse.de> (raw)
In-Reply-To: <20170315215107.5628-1-rgoldwyn@suse.de>
From: Goldwyn Rodrigues <rgoldwyn@suse.com>
Find out if the write will trigger a wait due to writeback. If yes,
return -EAGAIN.
This introduces a new function filemap_range_has_page() which
returns true if the file's mapping has a page within the range
mentioned.
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.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
include/linux/fs.h | 2 ++
mm/filemap.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 49 insertions(+), 3 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e8d9346..4a30e8f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2514,6 +2514,8 @@ extern int filemap_fdatawait(struct address_space *);
extern void filemap_fdatawait_keep_errors(struct address_space *);
extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
loff_t lend);
+extern int filemap_range_has_page(struct address_space *, loff_t lstart,
+ loff_t lend);
extern int filemap_write_and_wait(struct address_space *mapping);
extern int filemap_write_and_wait_range(struct address_space *mapping,
loff_t lstart, loff_t lend);
diff --git a/mm/filemap.c b/mm/filemap.c
index e08f3b9..c020e23 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -376,6 +376,39 @@ int filemap_flush(struct address_space *mapping)
}
EXPORT_SYMBOL(filemap_flush);
+/**
+ * filemap_range_has_page - check if a page exists in range.
+ * @mapping: address space structure to wait for
+ * @start_byte: offset in bytes where the range starts
+ * @end_byte: offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback.
+ */
+int filemap_range_has_page(struct address_space *mapping,
+ loff_t start_byte, loff_t end_byte)
+{
+ pgoff_t index = start_byte >> PAGE_SHIFT;
+ pgoff_t end = end_byte >> PAGE_SHIFT;
+ struct pagevec pvec;
+ int ret;
+
+ if (end_byte < start_byte)
+ return 0;
+
+ if (mapping->nrpages == 0)
+ return 0;
+
+ pagevec_init(&pvec, 0);
+ ret = pagevec_lookup(&pvec, mapping, index, 1);
+ if (!ret)
+ return 0;
+ ret = (pvec.pages[0]->index <= end);
+ pagevec_release(&pvec);
+ return ret;
+}
+EXPORT_SYMBOL(filemap_range_has_page);
+
static int __filemap_fdatawait_range(struct address_space *mapping,
loff_t start_byte, loff_t end_byte)
{
@@ -2640,6 +2673,9 @@ 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);
@@ -2709,9 +2745,17 @@ 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
--
2.10.2
next prev parent reply other threads:[~2017-03-15 21:51 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-15 21:50 [PATCH 0/8 v3] No wait AIO Goldwyn Rodrigues
2017-03-15 21:51 ` [PATCH 1/8] nowait aio: Introduce IOCB_RW_FLAG_NOWAIT Goldwyn Rodrigues
2017-03-15 21:51 ` [PATCH 2/8] nowait aio: Return if cannot get hold of i_rwsem Goldwyn Rodrigues
2017-03-15 21:51 ` Goldwyn Rodrigues [this message]
2017-03-16 13:08 ` [PATCH 3/8] nowait aio: return if direct write will trigger writeback Matthew Wilcox
2017-03-16 13:46 ` Goldwyn Rodrigues
2017-03-16 13:20 ` Matthew Wilcox
[not found] ` <20170316132052.GG4033-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org>
2017-03-16 13:46 ` Goldwyn Rodrigues
2017-03-15 21:51 ` [PATCH 4/8] nowait-aio: Introduce IOMAP_NOWAIT Goldwyn Rodrigues
2017-03-15 21:51 ` [PATCH 5/8] nowait aio: return on congested block device Goldwyn Rodrigues
[not found] ` <20170315215107.5628-6-rgoldwyn-l3A5Bk7waGM@public.gmane.org>
2017-03-16 14:33 ` Jens Axboe
2017-03-17 2:03 ` Ming Lei
2017-03-17 12:23 ` Goldwyn Rodrigues
[not found] ` <eee4683d-9f44-434f-b97f-b0b24c7b3dab-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>
2017-03-24 11:32 ` Goldwyn Rodrigues
2017-03-24 14:39 ` Jens Axboe
2017-03-16 21:31 ` Dave Chinner
2017-03-17 12:23 ` Goldwyn Rodrigues
2017-03-20 17:33 ` Jan Kara
2017-03-15 21:51 ` [PATCH 6/8] nowait aio: ext4 Goldwyn Rodrigues
2017-03-15 21:51 ` [PATCH 7/8] nowait aio: xfs Goldwyn Rodrigues
2017-03-15 21:51 ` [PATCH 8/8] nowait aio: btrfs Goldwyn Rodrigues
2017-04-03 18:52 [PATCH 0/8 v4] No wait AIO Goldwyn Rodrigues
2017-04-03 18:53 ` [PATCH 3/8] nowait aio: return if direct write will trigger writeback Goldwyn Rodrigues
2017-04-14 12:02 [PATCH 0/8 v6] No wait AIO Goldwyn Rodrigues
2017-04-14 12:02 ` [PATCH 3/8] nowait aio: return if direct write will trigger writeback Goldwyn Rodrigues
2017-05-09 12:22 [PATCH 0/8 v7] No wait AIO Goldwyn Rodrigues
2017-05-09 12:22 ` [PATCH 3/8] nowait aio: return if direct write will trigger writeback Goldwyn Rodrigues
2017-05-11 7:42 ` Christoph Hellwig
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