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[2003:cf:d737:d0cf:29d5:15fb:d605:1d53]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-439dad8d968sm26247465f8f.6.2026.03.09.08.09.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Mar 2026 08:09:58 -0700 (PDT) From: Hanna Czenczek To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Hanna Czenczek , Kevin Wolf , Brian Song Subject: [PATCH v5 22/25] fuse: Make shared export state atomic Date: Mon, 9 Mar 2026 16:08:53 +0100 Message-ID: <20260309150856.26800-23-hreitz@redhat.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260309150856.26800-1-hreitz@redhat.com> References: <20260309150856.26800-1-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=hreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -3 X-Spam_score: -0.4 X-Spam_bar: / X-Spam_report: (-0.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.819, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.903, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org The next commit is going to allow multi-threaded access to a FUSE export. In order to allow safe concurrent SETATTR operations that can modify the shared st_mode, st_uid, and st_gid, make any access to those fields atomic operations. Signed-off-by: Hanna Czenczek --- block/export/fuse.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) diff --git a/block/export/fuse.c b/block/export/fuse.c index 1c79411839..fe1b6ad5ff 100644 --- a/block/export/fuse.c +++ b/block/export/fuse.c @@ -156,6 +156,7 @@ typedef struct FuseExport { /* Whether allow_other was used as a mount option or not */ bool allow_other; + /* All atomic */ mode_t st_mode; uid_t st_uid; gid_t st_gid; @@ -266,6 +267,7 @@ static int fuse_export_create(BlockExport *blk_exp, ERRP_GUARD(); /* ensure clean-up even with error_fatal */ FuseExport *exp = container_of(blk_exp, FuseExport, common); BlockExportOptionsFuse *args = &blk_exp_args->u.fuse; + uint32_t st_mode; int ret; assert(blk_exp_args->type == BLOCK_EXPORT_TYPE_FUSE); @@ -334,12 +336,13 @@ static int fuse_export_create(BlockExport *blk_exp, args->allow_other = FUSE_EXPORT_ALLOW_OTHER_AUTO; } - exp->st_mode = S_IFREG | S_IRUSR; + st_mode = S_IFREG | S_IRUSR; if (exp->writable) { - exp->st_mode |= S_IWUSR; + st_mode |= S_IWUSR; } - exp->st_uid = getuid(); - exp->st_gid = getgid(); + qatomic_set(&exp->st_mode, st_mode); + qatomic_set(&exp->st_uid, getuid()); + qatomic_set(&exp->st_gid, getgid()); if (args->allow_other == FUSE_EXPORT_ALLOW_OTHER_AUTO) { /* Try allow_other == true first, ignore errors */ @@ -817,10 +820,10 @@ fuse_co_getattr(FuseExport *exp, struct fuse_attr_out *out) .attr_valid = 1, .attr = { .ino = 1, - .mode = exp->st_mode, + .mode = qatomic_read(&exp->st_mode), .nlink = 1, - .uid = exp->st_uid, - .gid = exp->st_gid, + .uid = qatomic_read(&exp->st_uid), + .gid = qatomic_read(&exp->st_gid), .size = length, .blksize = blk_bs(exp->common.blk)->bl.request_alignment, .blocks = allocated_blocks, @@ -903,15 +906,15 @@ fuse_co_setattr(FuseExport *exp, struct fuse_attr_out *out, uint32_t to_set, if (to_set & FATTR_MODE) { /* Ignore FUSE-supplied file type, only change the mode */ - exp->st_mode = (mode & 07777) | S_IFREG; + qatomic_set(&exp->st_mode, (mode & 07777) | S_IFREG); } if (to_set & FATTR_UID) { - exp->st_uid = uid; + qatomic_set(&exp->st_uid, uid); } if (to_set & FATTR_GID) { - exp->st_gid = gid; + qatomic_set(&exp->st_gid, gid); } return fuse_co_getattr(exp, out); -- 2.53.0