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buf SU hooks: track buf_start() calls with B_IOSTARTED flag

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and only call buf_complete() if previously started.  Some error paths,
like CoW failire, might skip buf_start() and do bufdone(), which itself
call buf_complete().

Various SU handle_written_XXX() functions check that io was started
and incomplete parts of the buffer data reverted before restoring them.
This is a useful invariant that B_IO_STARTED on buffer layer allows to
keep instead of changing check and panic into check and return.

Reported by:	pho
Reviewed by:	chs, mckusick
Tested by:	pho
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundations
This commit is contained in:
Konstantin Belousov 2021-01-30 04:10:34 +02:00
parent 0281f88e5d
commit bf0db19339
3 changed files with 27 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
sys/kern/vfs_bio.c
View File

@ -2639,6 +2639,13 @@ brelse(struct buf *bp)
return;
}
if (LIST_EMPTY(&bp->b_dep)) {
bp->b_flags &= ~B_IOSTARTED;
} else {
KASSERT((bp->b_flags & B_IOSTARTED) == 0,
("brelse: SU io not finished bp %p", bp));
}
if ((bp->b_vflags & (BV_BKGRDINPROG | BV_BKGRDERR)) == BV_BKGRDERR) {
BO_LOCK(bp->b_bufobj);
bp->b_vflags &= ~BV_BKGRDERR;
@ -2826,6 +2833,13 @@ bqrelse(struct buf *bp)
bp->b_flags &= ~(B_ASYNC | B_NOCACHE | B_AGE | B_RELBUF);
bp->b_xflags &= ~(BX_CVTENXIO);
if (LIST_EMPTY(&bp->b_dep)) {
bp->b_flags &= ~B_IOSTARTED;
} else {
KASSERT((bp->b_flags & B_IOSTARTED) == 0,
("bqrelse: SU io not finished bp %p", bp));
}
if (bp->b_flags & B_MANAGED) {
if (bp->b_flags & B_REMFREE)
bremfreef(bp);

16
sys/sys/buf.h
View File

@ -232,7 +232,7 @@ struct buf {
#define B_MALLOC 0x00010000 /* malloced b_data */
#define B_CLUSTEROK 0x00020000 /* Pagein op, so swap() can count it. */
#define B_INVALONERR 0x00040000 /* Invalidate on write error. */
#define B_00080000 0x00080000 /* Available flag. */
#define B_IOSTARTED 0x00080000 /* buf_start() called */
#define B_00100000 0x00100000 /* Available flag. */
#define B_MAXPHYS 0x00200000 /* nitems(b_pages[]) = atop(MAXPHYS). */
#define B_RELBUF 0x00400000 /* Release VMIO buffer. */
@ -248,8 +248,8 @@ struct buf {
#define PRINT_BUF_FLAGS "\20\40remfree\37cluster\36vmio\35ram\34managed" \
"\33paging\32infreecnt\31nocopy\30b23\27relbuf\26maxphys\25b20" \
"\24b19\23invalonerr\22clusterok\21malloc\20nocache\17b14\16inval" \
"\15reuse\14noreuse\13eintr\12done\11b8\10delwri" \
"\24iostarted\23invalonerr\22clusterok\21malloc\20nocache\17b14" \
"\16inval\15reuse\14noreuse\13eintr\12done\11b8\10delwri" \
"\7validsuspwrt\6cache\5deferred\4direct\3async\2needcommit\1age"
/*
@ -434,6 +434,9 @@ bstrategy(struct buf *bp)
static __inline void
buf_start(struct buf *bp)
{
KASSERT((bp->b_flags & B_IOSTARTED) == 0,
("recursed buf_start %p", bp));
bp->b_flags |= B_IOSTARTED;
if (bioops.io_start)
(*bioops.io_start)(bp);
}
@ -441,8 +444,11 @@ buf_start(struct buf *bp)
static __inline void
buf_complete(struct buf *bp)
{
if (bioops.io_complete)
(*bioops.io_complete)(bp);
if ((bp->b_flags & B_IOSTARTED) != 0) {
bp->b_flags &= ~B_IOSTARTED;
if (bioops.io_complete)
(*bioops.io_complete)(bp);
}
}
static __inline void

4
sys/ufs/ffs/ffs_vfsops.c
View File

@ -2393,10 +2393,10 @@ ffs_backgroundwritedone(struct buf *bp)
#endif
/*
* This buffer is marked B_NOCACHE so when it is released
* by biodone it will be tossed.
* by biodone it will be tossed. Clear B_IOSTARTED in case of error.
*/
bp->b_flags |= B_NOCACHE;
bp->b_flags &= ~B_CACHE;
bp->b_flags &= ~(B_CACHE | B_IOSTARTED);
pbrelvp(bp);
/*