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exterror(9): add infra for bufs and bios

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The extended error can be stored in either struct bio or struct buf,
indicated by BIO_EXTERR bio_flag.  At some strategic places, it is
copied into the current thread extended error.

This structure is required because io request from the top might pass
down through several io threads and the context that can report meaningful
extended error does not belong to the thread that initiated the io.

Sizes before the change, on amd64 nodebug:
sizeof(struct buf) =  456
sizeof(struct bio) = 376

after:
sizeof(struct buf) =  496
sizeof(struct bio) = 408

WIP: more geom providers should handle BIO_EXTERR when passing cloned
bios down and then handling completions.

Reviewed by:	mckusick
Sponsored by:	The FreeBSD Foundation
Differential revision:	https://reviews.freebsd.org/D53351
This commit is contained in:
Konstantin Belousov 2025-10-25 12:18:28 +03:00
parent 069e2fb550
commit 6c406b5b93
8 changed files with 54 additions and 11 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
sys/geom/geom_dev.c
View file

@ -734,6 +734,10 @@ g_dev_done(struct bio *bp2)
g_trace(G_T_BIO, "g_dev_done(%p) had error %d",
bp2, bp2->bio_error);
bp->bio_flags |= BIO_ERROR;
if ((bp2->bio_flags & BIO_EXTERR) != 0) {
bp->bio_flags |= BIO_EXTERR;
bp->bio_exterr = bp2->bio_exterr;
}
} else {
if (bp->bio_cmd == BIO_READ)
KNOTE_UNLOCKED(&sc->sc_selinfo.si_note, NOTE_READ);

10
sys/geom/geom_disk.c
View file

@ -235,8 +235,14 @@ g_disk_done(struct bio *bp)
bp2 = bp->bio_parent;
binuptime(&now);
mtx_lock(&sc->done_mtx);
if (bp2->bio_error == 0)
bp2->bio_error = bp->bio_error;
if (bp2->bio_error == 0) {
if ((bp->bio_flags & BIO_EXTERR) != 0) {
bp2->bio_flags |= BIO_EXTERR;
bp2->bio_exterr = bp->bio_exterr;
} else {
bp2->bio_error = bp->bio_error;
}
}
bp2->bio_completed += bp->bio_length - bp->bio_resid;
if (bp->bio_cmd == BIO_READ)

10
sys/geom/geom_subr.c
View file

@ -1162,8 +1162,14 @@ g_std_done(struct bio *bp)
struct bio *bp2;
bp2 = bp->bio_parent;
if (bp2->bio_error == 0)
bp2->bio_error = bp->bio_error;
if (bp2->bio_error == 0) {
if ((bp->bio_flags & BIO_EXTERR) != 0) {
bp2->bio_flags |= BIO_EXTERR;
bp2->bio_exterr = bp->bio_exterr;
} else {
bp2->bio_error = bp->bio_error;
}
}
bp2->bio_completed += bp->bio_completed;
g_destroy_bio(bp);
bp2->bio_inbed++;

7
sys/geom/geom_vfs.c
View file

@ -26,9 +26,11 @@
* SUCH DAMAGE.
*/
#define EXTERR_CATEGORY EXTERR_CAT_GEOMVFS
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bio.h>
#include <sys/exterrvar.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
@ -156,10 +158,13 @@ g_vfs_done(struct bio *bip)
" suppressing further ENXIO");
}
}
bp->b_error = bip->bio_error;
bp->b_ioflags = bip->bio_flags;
if (bip->bio_error)
bp->b_ioflags |= BIO_ERROR;
if ((bp->b_ioflags & BIO_EXTERR) != 0)
bp->b_exterr = bip->bio_exterr;
else
bp->b_error = bip->bio_error;
bp->b_resid = bp->b_bcount - bip->bio_completed;
g_destroy_bio(bip);

15
sys/kern/vfs_bio.c
View file

@ -44,6 +44,7 @@
* see man buf(9) for more info.
*/
#define EXTERR_CATEGORY EXTERR_CAT_VFSBIO
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/asan.h>
@ -55,6 +56,7 @@
#include <sys/counter.h>
#include <sys/devicestat.h>
#include <sys/eventhandler.h>
#include <sys/exterrvar.h>
#include <sys/fail.h>
#include <sys/ktr.h>
#include <sys/limits.h>
@ -1775,7 +1777,6 @@ buf_alloc(struct bufdomain *bd)
bp->b_blkno = bp->b_lblkno = 0;
bp->b_offset = NOOFFSET;
bp->b_iodone = 0;
bp->b_error = 0;
bp->b_resid = 0;
bp->b_bcount = 0;
bp->b_npages = 0;
@ -1785,6 +1786,7 @@ buf_alloc(struct bufdomain *bd)
bp->b_fsprivate1 = NULL;
bp->b_fsprivate2 = NULL;
bp->b_fsprivate3 = NULL;
exterr_clear(&bp->b_exterr);
LIST_INIT(&bp->b_dep);
return (bp);
@ -2276,7 +2278,7 @@ breadn_flags(struct vnode *vp, daddr_t blkno, daddr_t dblkno, int size,
}
if ((flags & GB_CVTENXIO) != 0)
bp->b_xflags |= BX_CVTENXIO;
bp->b_ioflags &= ~BIO_ERROR;
bp->b_ioflags &= ~(BIO_ERROR | BIO_EXTERR);
if (bp->b_rcred == NOCRED && cred != NOCRED)
bp->b_rcred = crhold(cred);
vfs_busy_pages(bp, 0);
@ -2353,7 +2355,7 @@ bufwrite(struct buf *bp)
bundirty(bp);
bp->b_flags &= ~B_DONE;
bp->b_ioflags &= ~BIO_ERROR;
bp->b_ioflags &= ~(BIO_ERROR | BIO_EXTERR);
bp->b_flags |= B_CACHE;
bp->b_iocmd = BIO_WRITE;
@ -4520,8 +4522,11 @@ biowait(struct bio *bp, const char *wmesg)
while ((bp->bio_flags & BIO_DONE) == 0)
msleep(bp, mtxp, PRIBIO, wmesg, 0);
mtx_unlock(mtxp);
if (bp->bio_error != 0)
if (bp->bio_error != 0) {
if ((bp->bio_flags & BIO_EXTERR) != 0)
return (exterr_set_from(&bp->bio_exterr));
return (bp->bio_error);
}
if (!(bp->bio_flags & BIO_ERROR))
return (0);
return (EIO);
@ -4568,6 +4573,8 @@ bufwait(struct buf *bp)
return (EINTR);
}
if (bp->b_ioflags & BIO_ERROR) {
if ((bp->b_ioflags & BIO_EXTERR) != 0)
exterr_set_from(&bp->b_exterr);
return (bp->b_error ? bp->b_error : EIO);
} else {
return (0);

7
sys/sys/bio.h
View file

@ -37,6 +37,7 @@
#ifndef _SYS_BIO_H_
#define _SYS_BIO_H_
#include <sys/_exterr.h>
#include <sys/queue.h>
#include <sys/disk_zone.h>
@ -65,6 +66,7 @@
#define BIO_TRANSIENT_MAPPING 0x20
#define BIO_VLIST 0x40
#define BIO_SWAP 0x200 /* Swap-related I/O */
#define BIO_EXTERR 0x2000
#define BIO_SPEEDUP_WRITE 0x4000 /* Resource shortage at upper layers */
#define BIO_SPEEDUP_TRIM 0x8000 /* Resource shortage at upper layers */
@ -94,7 +96,6 @@ struct bio {
struct vm_page **bio_ma; /* Or unmapped. */
int bio_ma_offset; /* Offset in the first page of bio_ma. */
int bio_ma_n; /* Number of pages in bio_ma. */
int bio_error; /* Errno for BIO_ERROR. */
long bio_resid; /* Remaining I/O in bytes. */
void (*bio_done)(struct bio *);
void *bio_driver1; /* Private use by the provider. */
@ -130,8 +131,12 @@ struct bio {
/* XXX: these go away when bio chaining is introduced */
daddr_t bio_pblkno; /* physical block number */
struct kexterr bio_exterr;
};
/* Errno for BIO_ERROR. */
#define bio_error bio_exterr.error
struct uio;
struct devstat;

10
sys/sys/buf.h
View file

@ -37,6 +37,7 @@
#ifndef _SYS_BUF_H_
#define _SYS_BUF_H_
#include <sys/_exterr.h>
#include <sys/bufobj.h>
#include <sys/queue.h>
#include <sys/lock.h>
@ -98,7 +99,6 @@ struct buf {
long b_bcount;
void *b_caller1;
caddr_t b_data;
int b_error;
uint16_t b_iocmd; /* BIO_* bio_cmd from bio.h */
uint16_t b_ioflags; /* BIO_* bio_flags from bio.h */
off_t b_iooffset;
@ -153,10 +153,12 @@ struct buf {
#elif defined(BUF_TRACKING)
const char *b_io_tracking;
#endif
struct kexterr b_exterr;
struct vm_page *b_pages[];
};
#define b_object b_bufobj->bo_object
#define b_error b_exterr.error
/*
* These flags are kept in b_flags.
@ -390,6 +392,12 @@ struct buf {
_lockmgr_disown(&(bp)->b_lock, LOCK_FILE, LOCK_LINE)
#endif
#define BUF_EXTERR_FROM_CURTHR(bp) \
bp->b_exterr = curthread->td_kexterr
#define BUF_EXTERR_TO_CURTHR(bp) \
curthread->td_kexterr = bp->b_exterr
#endif /* _KERNEL */
struct buf_queue_head {

2
sys/sys/exterr_cat.h
View file

@ -21,6 +21,8 @@
#define EXTERR_CAT_BRIDGE 7
#define EXTERR_CAT_SWAP 8
#define EXTERR_CAT_VFSSYSCALL 9
#define EXTERR_CAT_VFSBIO 10
#define EXTERR_CAT_GEOMVFS 11
#endif