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Tue, 21 Jan 2020 12:32:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579609954; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wJlj9UR2XHCaEOJQLlZ/XW9HF6zLHm2wx+mCl8HAA0Y=; b=ZImogR+S3uufgsGrTD11o0Qh9Qtyln873VqWjS/ugnbR20c7IJmd5mz2l9kJXZHZ/37vV+ SHFOU/kiY/tJLiHC+p4MZupfX/h7yZtzkRXqImiiNIgwMTO9cNokgRRDp/vYm3mVj/VGju 6QVdTfQxnanKejqO9gcPZOEkmFPcc8Q= From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com, berrange@redhat.com, slp@redhat.com, philmd@redhat.com Subject: [PATCH v2 099/109] virtiofsd: Fix data corruption with O_APPEND write in writeback mode Date: Tue, 21 Jan 2020 12:24:23 +0000 Message-Id: <20200121122433.50803-100-dgilbert@redhat.com> In-Reply-To: <20200121122433.50803-1-dgilbert@redhat.com> References: <20200121122433.50803-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: HgTz5zjWOQ6uhmEfYODL9Q-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: m.mizuma@jp.fujitsu.com, misono.tomohiro@jp.fujitsu.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" From: Misono Tomohiro When writeback mode is enabled (-o writeback), O_APPEND handling is done in kernel. Therefore virtiofsd clears O_APPEND flag when open. Otherwise O_APPEND flag takes precedence over pwrite() and write data may corrupt. Currently clearing O_APPEND flag is done in lo_open(), but we also need the same operation in lo_create(). So, factor out the flag update operation in lo_open() to update_open_flags() and call it in both lo_open() and lo_create(). This fixes the failure of xfstest generic/069 in writeback mode (which tests O_APPEND write data integrity). Signed-off-by: Misono Tomohiro Reviewed-by: Daniel P. Berrang=C3=A9 --- tools/virtiofsd/passthrough_ll.c | 66 ++++++++++++++++---------------- 1 file changed, 33 insertions(+), 33 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough= _ll.c index cadfa676ca..4482138904 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -1692,6 +1692,37 @@ static void lo_releasedir(fuse_req_t req, fuse_ino_t= ino, fuse_reply_err(req, 0); } =20 +static void update_open_flags(int writeback, struct fuse_file_info *fi) +{ + /* + * With writeback cache, kernel may send read requests even + * when userspace opened write-only + */ + if (writeback && (fi->flags & O_ACCMODE) =3D=3D O_WRONLY) { + fi->flags &=3D ~O_ACCMODE; + fi->flags |=3D O_RDWR; + } + + /* + * With writeback cache, O_APPEND is handled by the kernel. + * This breaks atomicity (since the file may change in the + * underlying filesystem, so that the kernel's idea of the + * end of the file isn't accurate anymore). In this example, + * we just accept that. A more rigorous filesystem may want + * to return an error here + */ + if (writeback && (fi->flags & O_APPEND)) { + fi->flags &=3D ~O_APPEND; + } + + /* + * O_DIRECT in guest should not necessarily mean bypassing page + * cache on host as well. If somebody needs that behavior, it + * probably should be a configuration knob in daemon. + */ + fi->flags &=3D ~O_DIRECT; +} + static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name, mode_t mode, struct fuse_file_info *fi) { @@ -1721,12 +1752,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t par= ent, const char *name, goto out; } =20 - /* - * O_DIRECT in guest should not necessarily mean bypassing page - * cache on host as well. If somebody needs that behavior, it - * probably should be a configuration knob in daemon. - */ - fi->flags &=3D ~O_DIRECT; + update_open_flags(lo->writeback, fi); =20 fd =3D openat(parent_inode->fd, name, (fi->flags | O_CREAT) & ~O_NOFOL= LOW, mode); @@ -1936,33 +1962,7 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, = struct fuse_file_info *fi) fuse_log(FUSE_LOG_DEBUG, "lo_open(ino=3D%" PRIu64 ", flags=3D%d)\n", i= no, fi->flags); =20 - /* - * With writeback cache, kernel may send read requests even - * when userspace opened write-only - */ - if (lo->writeback && (fi->flags & O_ACCMODE) =3D=3D O_WRONLY) { - fi->flags &=3D ~O_ACCMODE; - fi->flags |=3D O_RDWR; - } - - /* - * With writeback cache, O_APPEND is handled by the kernel. - * This breaks atomicity (since the file may change in the - * underlying filesystem, so that the kernel's idea of the - * end of the file isn't accurate anymore). In this example, - * we just accept that. A more rigorous filesystem may want - * to return an error here - */ - if (lo->writeback && (fi->flags & O_APPEND)) { - fi->flags &=3D ~O_APPEND; - } - - /* - * O_DIRECT in guest should not necessarily mean bypassing page - * cache on host as well. If somebody needs that behavior, it - * probably should be a configuration knob in daemon. - */ - fi->flags &=3D ~O_DIRECT; + update_open_flags(lo->writeback, fi); =20 sprintf(buf, "%i", lo_fd(req, ino)); fd =3D openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW); --=20 2.24.1