Date: Mon, 25 May 2020 04:56:41 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r361440 - head/sys/kern Message-ID: <202005250456.04P4ufcs051922@repo.freebsd.org>
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Author: mjg Date: Mon May 25 04:56:41 2020 New Revision: 361440 URL: https://svnweb.freebsd.org/changeset/base/361440 Log: vfs: restore mtx-protected foffset locking for 32 bit platforms They depend on it to accurately read the offset. The new code is not used as it would add an interrupt enable/disable trip on top of the atomic. This also fixes a bug where 32-bit nolock request would still lock the offset. No changes for 64-bit. Reported by: emaste Modified: head/sys/kern/vfs_vnops.c Modified: head/sys/kern/vfs_vnops.c ============================================================================== --- head/sys/kern/vfs_vnops.c Mon May 25 04:17:01 2020 (r361439) +++ head/sys/kern/vfs_vnops.c Mon May 25 04:56:41 2020 (r361440) @@ -672,6 +672,7 @@ vn_rdwr_inchunks(enum uio_rw rw, struct vnode *vp, voi return (error); } +#if OFF_MAX <= LONG_MAX off_t foffset_lock(struct file *fp, int flags) { @@ -681,14 +682,12 @@ foffset_lock(struct file *fp, int flags) KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed")); -#if OFF_MAX <= LONG_MAX /* * Caller only wants the current f_offset value. Assume that * the long and shorter integer types reads are atomic. */ if ((flags & FOF_NOLOCK) != 0) return (fp->f_offset); -#endif /* * According to McKusick the vn lock was protecting f_offset here. @@ -737,10 +736,8 @@ foffset_unlock(struct file *fp, off_t val, int flags) if ((flags & FOF_NEXTOFF) != 0) fp->f_nextoff = val; -#if OFF_MAX <= LONG_MAX if ((flags & FOF_NOLOCK) != 0) return; -#endif flagsp = &fp->f_vnread_flags; state = atomic_load_16(flagsp); @@ -755,6 +752,53 @@ foffset_unlock(struct file *fp, off_t val, int flags) sleepq_broadcast(&fp->f_vnread_flags, SLEEPQ_SLEEP, 0, 0); sleepq_release(&fp->f_vnread_flags); } +#else +off_t +foffset_lock(struct file *fp, int flags) +{ + struct mtx *mtxp; + off_t res; + + KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed")); + + mtxp = mtx_pool_find(mtxpool_sleep, fp); + mtx_lock(mtxp); + if ((flags & FOF_NOLOCK) == 0) { + while (fp->f_vnread_flags & FOFFSET_LOCKED) { + fp->f_vnread_flags |= FOFFSET_LOCK_WAITING; + msleep(&fp->f_vnread_flags, mtxp, PUSER -1, + "vofflock", 0); + } + fp->f_vnread_flags |= FOFFSET_LOCKED; + } + res = fp->f_offset; + mtx_unlock(mtxp); + return (res); +} + +void +foffset_unlock(struct file *fp, off_t val, int flags) +{ + struct mtx *mtxp; + + KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed")); + + mtxp = mtx_pool_find(mtxpool_sleep, fp); + mtx_lock(mtxp); + if ((flags & FOF_NOUPDATE) == 0) + fp->f_offset = val; + if ((flags & FOF_NEXTOFF) != 0) + fp->f_nextoff = val; + if ((flags & FOF_NOLOCK) == 0) { + KASSERT((fp->f_vnread_flags & FOFFSET_LOCKED) != 0, + ("Lost FOFFSET_LOCKED")); + if (fp->f_vnread_flags & FOFFSET_LOCK_WAITING) + wakeup(&fp->f_vnread_flags); + fp->f_vnread_flags = 0; + } + mtx_unlock(mtxp); +} +#endif void foffset_lock_uio(struct file *fp, struct uio *uio, int flags)
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