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authorJens Axboe <axboe@kernel.dk>2020-10-17 08:31:29 -0600
committerJens Axboe <axboe@kernel.dk>2020-10-17 13:49:05 -0600
commit13bd691421bc191a402d2e0d3da5f248d170a632 (patch)
tree464cd1511166ea7adb526f7f1911755d7833bb7f /mm
parent58852d4d673760cf7c88b9360b3c24a041bec298 (diff)
mm: mark async iocb read as NOWAIT once some data has been copied
Once we've copied some data for an iocb that is marked with IOCB_WAITQ, we should no longer attempt to async lock a new page. Instead make sure we return the copied amount, and let the caller retry, instead of returning -EIOCBQUEUED for a new page. This should only be possible with read-ahead disabled on the below device, and multiple threads racing on the same file. Haven't been able to reproduce on anything else. Cc: stable@vger.kernel.org # v5.9 Fixes: 1a0a7853b901 ("mm: support async buffered reads in generic_file_buffered_read()") Reported-by: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'mm')
-rw-r--r--mm/filemap.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 1a6beaf69f49..e4101b5bfa82 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2199,6 +2199,14 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,
last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
offset = *ppos & ~PAGE_MASK;
+ /*
+ * If we've already successfully copied some data, then we
+ * can no longer safely return -EIOCBQUEUED. Hence mark
+ * an async read NOWAIT at that point.
+ */
+ if (written && (iocb->ki_flags & IOCB_WAITQ))
+ iocb->ki_flags |= IOCB_NOWAIT;
+
for (;;) {
struct page *page;
pgoff_t end_index;