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CVS commit: src/sys/kern

Module Name:    src
Committed By:   reinoud
Date:           Wed Dec 22 14:05:51 UTC 2010

Modified Files:
        src/sys/kern: vfs_bio.c

Log Message:
Fix nestio's behavior on error.

The mbp->b_resid is used to track if all the nested buffers have been issued
and reported back. When the last buffer calls in, mbp->b_resid becomes zero
and biodone(mbp) is called. This is fine as long as there are no errors.

If a read-error does occure in one of the nested buffers, the mbp->b_error is
set and on its call to biodone(mbp), with mbp->b_resid is zero, physio()
panics since it asserts that IF an error is set on a buffer, there should be a
residual amount of data left to transfered.

The patch fixes this case by setting mbp->b_resid back to mbp->b_bcount on
mbp->b_error just before biodone(mbp).

This behaviour is consistent with normal buffer issueing. It either succeeds
or doesn't succeed.

To generate a diff of this commit:
cvs rdiff -u -r1.225 -r1.226 src/sys/kern/vfs_bio.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.

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