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Wong" , Paul Mackerras Date: Tue, 3 Aug 2021 21:18:06 +0200 Message-Id: <20210803191818.993968-1-agruenba@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Proofpoint-SPF-Result: pass X-Proofpoint-SPF-Record: v=spf1 ip4:103.23.64.2 ip4:103.23.65.2 ip4:103.23.66.26 ip4:103.23.67.26 ip4:107.21.15.141 ip4:108.177.8.0/21 ip4:128.17.0.0/20 ip4:128.17.128.0/20 ip4:128.17.192.0/20 ip4:128.17.64.0/20 ip4:128.245.0.0/20 ip4:128.245.64.0/20 ip4:13.110.208.0/21 ip4:13.111.0.0/16 ip4:136.147.128.0/20 ip4:136.147.176.0/20 ip4:148.105.8.0/21 ip4:148.139.0.2 include:spf1.redhat.com -all X-Proofpoint-SPF-VenPass: Allowed X-Source-IP: 170.10.133.124 X-ServerName: us-smtp-delivery-124.mimecast.com X-Proofpoint-SPF-Result: pass X-Proofpoint-SPF-Record: v=spf1 ip4:103.23.64.2 ip4:103.23.65.2 ip4:103.23.66.26 ip4:103.23.67.26 ip4:107.21.15.141 ip4:108.177.8.0/21 ip4:128.17.0.0/20 ip4:128.17.128.0/20 ip4:128.17.192.0/20 ip4:128.17.64.0/20 ip4:128.245.0.0/20 ip4:128.245.64.0/20 ip4:13.110.208.0/21 ip4:13.111.0.0/16 ip4:136.147.128.0/20 ip4:136.147.176.0/20 ip4:148.105.8.0/21 ip4:148.139.0.2 include:spf1.redhat.com -all X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10065 signatures=668682 X-Proofpoint-Spam-Reason: safe X-Spam: OrgSafeList X-SpamRule: orgsafelist X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10065 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 malwarescore=0 phishscore=0 spamscore=0 adultscore=0 suspectscore=0 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108030123 Cc: Jan Kara , Andreas Gruenbacher , linux-kernel@vger.kernel.org, cluster-devel@redhat.com, kvm-ppc@vger.kernel.org, linux-fsdevel@vger.kernel.org, ocfs2-devel@oss.oracle.com Subject: [Ocfs2-devel] [PATCH v5 00/12] gfs2: Fix mmap + page fault deadlocks X-BeenThere: ocfs2-devel@oss.oracle.com X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: ocfs2-devel-bounces@oss.oracle.com Errors-To: ocfs2-devel-bounces@oss.oracle.com X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10065 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 phishscore=0 malwarescore=0 suspectscore=0 mlxscore=0 adultscore=0 mlxlogscore=999 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108030123 X-Proofpoint-GUID: RRkUPneoTTVh4wyfKX69bh74xSgYWL9E X-Proofpoint-ORIG-GUID: RRkUPneoTTVh4wyfKX69bh74xSgYWL9E Hi all, here's another update on top of v5.14-rc4. There seems to be a bug in get_user_pages_fast when called with FOLL_FAST_ONLY; please see below. Changes: * Change fault_in_pages_{readable,writeable} to return the number of bytes that should be accessible instead of failing outright when part of the requested region cannot be faulted in. Change iov_iter_fault_in_readable to those same semantics. * Add fault_in_iov_iter_writeable for safely faulting in pages for writing without modifying the pages. With this patch queue, fstest generic/208 (aio-dio-invalidate-failure.c) endlessly spins in gfs2_file_direct_write. It looks as if there's a bug in get_user_pages_fast when called with FOLL_FAST_ONLY: (1) The test case performs an aio write into a 32 MB buffer. (2) The buffer is initially not in memory, so when iomap_dio_rw() -> ... -> bio_iov_iter_get_pages() is called with the iter->noio flag set, we get to get_user_pages_fast() with FOLL_FAST_ONLY set. get_user_pages_fast() returns 0, which causes bio_iov_iter_get_pages to return -EFAULT. (3) Then gfs2_file_direct_write faults in the entire buffer with fault_in_iov_iter_readable(), which succeeds. (4) With the buffer in memory, we retry the iomap_dio_rw() -> ... -> bio_iov_iter_get_pages() -> ... -> get_user_pages_fast(). This should succeed now, but get_user_pages_fast() still returns 0. (5) Thus we end up in step (3) again. The buffered writes generic/208 performs are unrelated to this hang. Apart from the generic/208 hang, gfs2 still needs a better strategy for faulting in more reasonable chunks of memory at a time and for resuming requests after faulting in pages. We've got some of the pieces in place for safely allowing that, but more work remains to be done. For immediate consideration by Al Viro: iov_iter: Fix iov_iter_get_pages{,_alloc} page fault return value For immediate consideration by Paul Mackerras: powerpc/kvm: Fix kvm_use_magic_page Thanks, Andreas Andreas Gruenbacher (12): iov_iter: Fix iov_iter_get_pages{,_alloc} page fault return value powerpc/kvm: Fix kvm_use_magic_page Turn fault_in_pages_{readable,writeable} into fault_in_{readable,writeable} Turn iov_iter_fault_in_readable into fault_in_iov_iter_readable iov_iter: Introduce fault_in_iov_iter_writeable gfs2: Add wrapper for iomap_file_buffered_write gfs2: Fix mmap + page fault deadlocks for buffered I/O iomap: Fix iomap_dio_rw return value for user copies iomap: Support restarting direct I/O requests after user copy failures iomap: Add done_before argument to iomap_dio_rw iov_iter: Introduce noio flag to disable page faults gfs2: Fix mmap + page fault deadlocks for direct I/O arch/powerpc/kernel/kvm.c | 3 +- arch/powerpc/kernel/signal_32.c | 4 +- arch/powerpc/kernel/signal_64.c | 2 +- arch/x86/kernel/fpu/signal.c | 8 +- drivers/gpu/drm/armada/armada_gem.c | 7 +- fs/btrfs/file.c | 8 +- fs/btrfs/ioctl.c | 7 +- fs/ext4/file.c | 5 +- fs/f2fs/file.c | 6 +- fs/fuse/file.c | 2 +- fs/gfs2/file.c | 95 ++++++++++++++++++++--- fs/iomap/buffered-io.c | 2 +- fs/iomap/direct-io.c | 28 +++++-- fs/ntfs/file.c | 2 +- fs/xfs/xfs_file.c | 6 +- fs/zonefs/super.c | 4 +- include/linux/iomap.h | 11 ++- include/linux/pagemap.h | 58 +------------- include/linux/uio.h | 4 +- lib/iov_iter.c | 107 ++++++++++++++++++++------ mm/filemap.c | 4 +- mm/gup.c | 113 ++++++++++++++++++++++++++++ 22 files changed, 360 insertions(+), 126 deletions(-) -- 2.26.3 _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel