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| author |   Goldwyn Rodrigues <rgoldwyn@suse.com> | 2017-06-20 07:05:46 -0500 |
|---|---|---|
| committer |   Jens Axboe <axboe@kernel.dk> | 2017-06-20 07:12:03 -0600 |
| commit | 03a07c92a9ed9938d828ca7f1d11b8bc63a7bb89 (patch) | |
| tree | aced260faa3cdf56d6f1140579ffaf46f8ba9c25 /include/linux/blk_types.h | |
| parent | fs: Introduce IOMAP_NOWAIT (diff) | |
| download | linux-dev-03a07c92a9ed9938d828ca7f1d11b8bc63a7bb89.tar.xz linux-dev-03a07c92a9ed9938d828ca7f1d11b8bc63a7bb89.zip | |
block: return on congested block device
A new bio operation flag REQ_NOWAIT is introduced to identify bio's
orignating from iocb with IOCB_NOWAIT. This flag indicates
to return immediately if a request cannot be made instead
of retrying.
Stacked devices such as md (the ones with make_request_fn hooks)
currently are not supported because it may block for housekeeping.
For example, an md can have a part of the device suspended.
For this reason, only request based devices are supported.
In the future, this feature will be expanded to stacked devices
by teaching them how to handle the REQ_NOWAIT flags.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/linux/blk_types.h')
| -rw-r--r-- | include/linux/blk_types.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index dcd45b15a3a5..e210da6d14b8 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -36,6 +36,8 @@ typedef u8 __bitwise blk_status_t; /* hack for device mapper, don't use elsewhere: */ #define BLK_STS_DM_REQUEUE ((__force blk_status_t)11) +#define BLK_STS_AGAIN ((__force blk_status_t)12) + struct blk_issue_stat { u64 stat; }; @@ -224,6 +226,7 @@ enum req_flag_bits { /* command specific flags for REQ_OP_WRITE_ZEROES: */ __REQ_NOUNMAP, /* do not free blocks when zeroing */ + __REQ_NOWAIT, /* Don't wait if request will block */ __REQ_NR_BITS, /* stops here */ }; @@ -242,6 +245,7 @@ enum req_flag_bits { #define REQ_BACKGROUND (1ULL << __REQ_BACKGROUND) #define REQ_NOUNMAP (1ULL << __REQ_NOUNMAP) +#define REQ_NOWAIT (1ULL << __REQ_NOWAIT) #define REQ_FAILFAST_MASK \ (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER) |