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With the removal of b_saveaddr in the r285819, b_data must be reset to

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b_kvabase when the buffer is reclaimed.  Otherwise, if b_data for the
mapped buffer was adjusted with the page-offset portion of b_offset,
nothing would re-adjust the b_data, which breaks buffer management
code which expects page-aligned b_data (see e.g. bpman_qenter(), which
skips partial pages).

Fix a minor issue with the GB_KVAALLOC requests, which could result in
returning the mapped buffer if the reused buffer is mapped and have
the right amount of KVA reserved.

Improve assertion in the vfs_buf_check_mapped() to catch unmapped
buffers which have their b_data incorrectly adjusted with offset.

Reported and tested by:	pho (previous version)
Reviewed by:	jeff (previous version)
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
kib 2015-07-25 15:00:14 +00:00
parent 2fcd3be83e
commit 4f745f69b4
1 changed files with 7 additions and 0 deletions
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7
sys/kern/vfs_bio.c
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@ -956,6 +956,8 @@ vfs_buf_check_mapped(struct buf *bp)
("mapped buf: b_kvabase was not updated %p", bp));
KASSERT(bp->b_data != unmapped_buf,
("mapped buf: b_data was not updated %p", bp));
KASSERT(bp->b_data < unmapped_buf || bp->b_data > unmapped_buf +
MAXPHYS, ("b_data + b_offset unmapped %p", bp));
}
static inline void
@ -2241,6 +2243,7 @@ getnewbuf_reuse_bp(struct buf *bp, int qindex)
bp->b_dirtyoff = bp->b_dirtyend = 0;
bp->b_bufobj = NULL;
bp->b_pin_count = 0;
bp->b_data = bp->b_kvabase;
bp->b_fsprivate1 = NULL;
bp->b_fsprivate2 = NULL;
bp->b_fsprivate3 = NULL;
@ -2528,6 +2531,10 @@ getnewbuf(struct vnode *vp, int slpflag, int slptimeo, int size, int maxsize,
bp->b_flags |= B_INVAL;
brelse(bp);
goto restart;
} else if ((gbflags & (GB_UNMAPPED | GB_KVAALLOC)) ==
(GB_UNMAPPED | GB_KVAALLOC)) {
bp->b_data = unmapped_buf;
BUF_CHECK_UNMAPPED(bp);
}
atomic_add_int(&bufreusecnt, 1);
}