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authorColy Li <colyli@suse.de>2019-06-28 19:59:29 +0800
committerJens Axboe <axboe@kernel.dk>2019-06-28 07:39:14 -0600
commit578df99b1b0531d19af956530fe4da63d01a1604 (patch)
treefc8d3d317790dffc9f8651f8f59517d11ef3f977
parente6dcbd3e6c91b7828cb305ec324eb7fd9bdea8a0 (diff)
downloadlinux-578df99b1b0531d19af956530fe4da63d01a1604.tar.bz2
bcache: ignore read-ahead request failure on backing device
When md raid device (e.g. raid456) is used as backing device, read-ahead requests on a degrading and recovering md raid device might be failured immediately by md raid code, but indeed this md raid array can still be read or write for normal I/O requests. Therefore such failed read-ahead request are not real hardware failure. Further more, after degrading and recovering accomplished, read-ahead requests will be handled by md raid array again. For such condition, I/O failures of read-ahead requests don't indicate real health status (because normal I/O still be served), they should not be counted into I/O error counter dc->io_errors. Since there is no simple way to detect whether the backing divice is a md raid device, this patch simply ignores I/O failures for read-ahead bios on backing device, to avoid bogus backing device failure on a degrading md raid array. Suggested-and-tested-by: Thorsten Knabe <linux@thorsten-knabe.de> Signed-off-by: Coly Li <colyli@suse.de> Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--drivers/md/bcache/io.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/md/bcache/io.c b/drivers/md/bcache/io.c
index c25097968319..4d93f07f63e5 100644
--- a/drivers/md/bcache/io.c
+++ b/drivers/md/bcache/io.c
@@ -58,6 +58,18 @@ void bch_count_backing_io_errors(struct cached_dev *dc, struct bio *bio)
WARN_ONCE(!dc, "NULL pointer of struct cached_dev");
+ /*
+ * Read-ahead requests on a degrading and recovering md raid
+ * (e.g. raid6) device might be failured immediately by md
+ * raid code, which is not a real hardware media failure. So
+ * we shouldn't count failed REQ_RAHEAD bio to dc->io_errors.
+ */
+ if (bio->bi_opf & REQ_RAHEAD) {
+ pr_warn_ratelimited("%s: Read-ahead I/O failed on backing device, ignore",
+ dc->backing_dev_name);
+ return;
+ }
+
errors = atomic_add_return(1, &dc->io_errors);
if (errors < dc->error_limit)
pr_err("%s: IO error on backing device, unrecoverable",