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zvol: Remove broken blk-mq optimization

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This fix removes a dubious optimization in zfs_uiomove_bvec_rq()
that saved the iterator contents of a rq_for_each_segment().  This
optimization allowed restoring the "saved state" from a previous
rq_for_each_segment() call on the same uio so that you wouldn't
need to iterate though each bvec on every zfs_uiomove_bvec_rq() call.
However, if the kernel is manipulating the requests/bios/bvecs under
the covers between zfs_uiomove_bvec_rq() calls, then it could result
in corruption from using the "saved state".  This optimization
results in an unbootable system after installing an OS on a zvol
with blk-mq enabled.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #15351
This commit is contained in:
Tony Hutter
2023-10-23 14:45:06 -07:00
parent 86c3ed40e1
commit e860cb0200
2 changed files with 0 additions and 37 deletions
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include/os/linux/spl/sys/uio.h
-8
View File
@@ -73,13 +73,6 @@ typedef struct zfs_uio {
size_t uio_skip;
struct request *rq;
/*
* Used for saving rq_for_each_segment() state between calls
* to zfs_uiomove_bvec_rq().
*/
struct req_iterator iter;
struct bio_vec bv;
} zfs_uio_t;
@@ -138,7 +131,6 @@ zfs_uio_bvec_init(zfs_uio_t *uio, struct bio *bio, struct request *rq)
} else {
uio->uio_bvec = NULL;
uio->uio_iovcnt = 0;
memset(&uio->iter, 0, sizeof (uio->iter));
}
uio->uio_loffset = io_offset(bio, rq);