Author: cem Date: Fri Jul 31 00:07:01 2020 New Revision: 363721 URL: https://svnweb.freebsd.org/changeset/base/363721
Log: getblk: Avoid sleeping on wrong buf in lockless path If the buffer identity changed during lookup, sleeping could introduce a lock order reversal. Since we do not know if the identity changed until we get the lock, we must try-lock (LK_NOWAIT) only. EINTR and ERESTART error handling becomes irrelevant, as we no longer sleep. Reported by: kib Reviewed by: kib X-MFC-With: r363482 Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D25898 Modified: head/sys/kern/vfs_bio.c Modified: head/sys/kern/vfs_bio.c ============================================================================== --- head/sys/kern/vfs_bio.c Thu Jul 30 23:54:25 2020 (r363720) +++ head/sys/kern/vfs_bio.c Fri Jul 31 00:07:01 2020 (r363721) @@ -3844,7 +3844,7 @@ getblkx(struct vnode *vp, daddr_t blkno, daddr_t dblkn struct buf *bp; struct bufobj *bo; daddr_t d_blkno; - int bsize, error, maxsize, vmio, lockflags; + int bsize, error, maxsize, vmio; off_t offset; CTR3(KTR_BUF, "getblk(%p, %ld, %d)", vp, (long)blkno, size); @@ -3865,14 +3865,9 @@ getblkx(struct vnode *vp, daddr_t blkno, daddr_t dblkn if (bp == NULL) goto newbuf_unlocked; - lockflags = LK_EXCLUSIVE | LK_SLEEPFAIL | - ((flags & GB_LOCK_NOWAIT) ? LK_NOWAIT : 0); - - error = BUF_TIMELOCK(bp, lockflags, NULL, "getblku", slpflag, - slptimeo); - if (error == EINTR || error == ERESTART) - return (error); - else if (error != 0) + error = BUF_TIMELOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL, "getblku", 0, + 0); + if (error != 0) goto loop; /* Verify buf identify has not changed since lookup. */ @@ -3886,6 +3881,8 @@ loop: BO_RLOCK(bo); bp = gbincore(bo, blkno); if (bp != NULL) { + int lockflags; + /* * Buffer is in-core. If the buffer is not busy nor managed, * it must be on a queue. _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
