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block: use 32-bit blk_status_t on Alpha
commit 6e2fb22103
upstream.
Early alpha processors cannot write a single byte or word; they read 8
bytes, modify the value in registers and write back 8 bytes.
The type blk_status_t is defined as one byte, it is often written
asynchronously by I/O completion routines, this asynchronous modification
can corrupt content of nearby bytes if these nearby bytes can be written
simultaneously by another CPU.
- one example of such corruption is the structure dm_io where
"blk_status_t status" is written by an asynchronous completion routine
and "atomic_t io_count" is modified synchronously
- another example is the structure dm_buffer where "unsigned hold_count"
is modified synchronously from process context and "blk_status_t
write_error" is modified asynchronously from bio completion routine
This patch fixes the bug by changing the type blk_status_t to 32 bits if
we are on Alpha and if we are compiling for a processor that doesn't have
the byte-word-extension.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org # 4.13+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -20,8 +20,13 @@ typedef void (bio_end_io_t) (struct bio *);
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/*
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* Block error status values. See block/blk-core:blk_errors for the details.
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* Alpha cannot write a byte atomically, so we need to use 32-bit value.
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*/
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#if defined(CONFIG_ALPHA) && !defined(__alpha_bwx__)
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typedef u32 __bitwise blk_status_t;
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#else
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typedef u8 __bitwise blk_status_t;
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#endif
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#define BLK_STS_OK 0
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#define BLK_STS_NOTSUPP ((__force blk_status_t)1)
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#define BLK_STS_TIMEOUT ((__force blk_status_t)2)
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