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bh=h0+ghJ5Sv0SORUEp9BeRfqdslF+Xrc9zeLUiqNtoejU=; b=WAOMtHhNZNxfgxm4OBamiyNGPAJQMxUKcHk7TNl3DKge4GeYXU8Z5c6815Y9myKI0B6s/h kRAqX7gklmLsQCNWPqrVAhIkH/uFqMgcUAy9rT08Olm5x5it21kQtVnJyiLBuSuMeYy2os /736ue0SKaPfqrgp1jUidjdAPOCBHnw= X-MC-Unique: 8Gp9NcPwPJCz93ARxjAMTA-1 From: Max Reitz To: qemu-block@nongnu.org Subject: [PATCH v2 03/20] fuse: Implement standard FUSE operations Date: Tue, 22 Sep 2020 12:49:15 +0200 Message-Id: <20200922104932.46384-4-mreitz@redhat.com> In-Reply-To: <20200922104932.46384-1-mreitz@redhat.com> References: <20200922104932.46384-1-mreitz@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; 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charset="utf-8" This makes the export actually useful instead of only producing errors whenever it is accessed. Signed-off-by: Max Reitz --- block/export/fuse.c | 226 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 226 insertions(+) diff --git a/block/export/fuse.c b/block/export/fuse.c index 75f11d2514..8fc667231d 100644 --- a/block/export/fuse.c +++ b/block/export/fuse.c @@ -32,6 +32,10 @@ #include =20 =20 +/* Prevent overly long bounce buffer allocations */ +#define FUSE_MAX_BOUNCE_BYTES (MIN(BDRV_REQUEST_MAX_BYTES, 64 * 1024 * 102= 4)) + + typedef struct FuseExport { BlockExport common; =20 @@ -241,7 +245,229 @@ static bool is_regular_file(const char *path, Error *= *errp) return true; } =20 + +/** + * Let clients look up files. Always return ENOENT because we only + * care about the mountpoint itself. + */ +static void fuse_lookup(fuse_req_t req, fuse_ino_t parent, const char *nam= e) +{ + fuse_reply_err(req, ENOENT); +} + +/** + * Let clients get file attributes (i.e., stat() the file). + */ +static void fuse_getattr(fuse_req_t req, fuse_ino_t inode, + struct fuse_file_info *fi) +{ + struct stat statbuf; + int64_t length, allocated_blocks; + time_t now =3D time(NULL); + ImageInfo *info =3D NULL; + FuseExport *exp =3D fuse_req_userdata(req); + mode_t mode; + Error *local_error =3D NULL; + + length =3D blk_getlength(exp->common.blk); + if (length < 0) { + fuse_reply_err(req, -length); + return; + } + + bdrv_query_image_info(blk_bs(exp->common.blk), &info, &local_error); + if (local_error) { + allocated_blocks =3D DIV_ROUND_UP(length, 512); + } else { + allocated_blocks =3D DIV_ROUND_UP(info->actual_size, 512); + } + + qapi_free_ImageInfo(info); + error_free(local_error); + local_error =3D NULL; + + mode =3D S_IFREG | S_IRUSR; + if (exp->writable) { + mode |=3D S_IWUSR; + } + + statbuf =3D (struct stat) { + .st_ino =3D inode, + .st_mode =3D mode, + .st_nlink =3D 1, + .st_uid =3D getuid(), + .st_gid =3D getgid(), + .st_size =3D length, + .st_blksize =3D blk_bs(exp->common.blk)->bl.request_alignment, + .st_blocks =3D allocated_blocks, + .st_atime =3D now, + .st_mtime =3D now, + .st_ctime =3D now, + }; + + fuse_reply_attr(req, &statbuf, 1.); +} + +static int fuse_do_truncate(const FuseExport *exp, int64_t size, + PreallocMode prealloc) +{ + uint64_t blk_perm, blk_shared_perm; + int ret; + + blk_get_perm(exp->common.blk, &blk_perm, &blk_shared_perm); + + ret =3D blk_set_perm(exp->common.blk, blk_perm | BLK_PERM_RESIZE, + blk_shared_perm, NULL); + if (ret < 0) { + return ret; + } + + ret =3D blk_truncate(exp->common.blk, size, true, prealloc, 0, NULL); + + /* Must succeed, because we are only giving up the RESIZE permission */ + blk_set_perm(exp->common.blk, blk_perm, blk_shared_perm, &error_abort); + + return ret; +} + +/** + * Let clients set file attributes. Only resizing is supported. + */ +static void fuse_setattr(fuse_req_t req, fuse_ino_t inode, struct stat *st= atbuf, + int to_set, struct fuse_file_info *fi) +{ + FuseExport *exp =3D fuse_req_userdata(req); + int ret; + + if (!exp->writable) { + fuse_reply_err(req, EACCES); + return; + } + + if (to_set & ~FUSE_SET_ATTR_SIZE) { + fuse_reply_err(req, ENOTSUP); + return; + } + + ret =3D fuse_do_truncate(exp, statbuf->st_size, PREALLOC_MODE_OFF); + if (ret < 0) { + fuse_reply_err(req, -ret); + return; + } + + fuse_getattr(req, inode, fi); +} + +/** + * Let clients open a file (i.e., the exported image). + */ +static void fuse_open(fuse_req_t req, fuse_ino_t inode, + struct fuse_file_info *fi) +{ + fuse_reply_open(req, fi); +} + +/** + * Handle client reads from the exported image. + */ +static void fuse_read(fuse_req_t req, fuse_ino_t inode, + size_t size, off_t offset, struct fuse_file_info *fi) +{ + FuseExport *exp =3D fuse_req_userdata(req); + int64_t length; + void *buf; + int ret; + + /** + * Clients will expect short reads at EOF, so we have to limit + * offset+size to the image length. + */ + length =3D blk_getlength(exp->common.blk); + if (length < 0) { + fuse_reply_err(req, -length); + return; + } + + size =3D MIN(size, FUSE_MAX_BOUNCE_BYTES); + if (offset + size > length) { + size =3D length - offset; + } + + buf =3D qemu_try_blockalign(blk_bs(exp->common.blk), size); + if (!buf) { + fuse_reply_err(req, ENOMEM); + return; + } + + ret =3D blk_pread(exp->common.blk, offset, buf, size); + if (ret >=3D 0) { + fuse_reply_buf(req, buf, size); + } else { + fuse_reply_err(req, -ret); + } + + qemu_vfree(buf); +} + +/** + * Handle client writes to the exported image. + */ +static void fuse_write(fuse_req_t req, fuse_ino_t inode, const char *buf, + size_t size, off_t offset, struct fuse_file_info *f= i) +{ + FuseExport *exp =3D fuse_req_userdata(req); + int64_t length; + int ret; + + if (!exp->writable) { + fuse_reply_err(req, EACCES); + return; + } + + /** + * Clients will expect short writes at EOF, so we have to limit + * offset+size to the image length. + */ + length =3D blk_getlength(exp->common.blk); + if (length < 0) { + fuse_reply_err(req, -length); + return; + } + + size =3D MIN(size, BDRV_REQUEST_MAX_BYTES); + if (offset + size > length) { + size =3D length - offset; + } + + ret =3D blk_pwrite(exp->common.blk, offset, buf, size, 0); + if (ret >=3D 0) { + fuse_reply_write(req, size); + } else { + fuse_reply_err(req, -ret); + } +} + +/** + * Let clients flush the exported image. + */ +static void fuse_flush(fuse_req_t req, fuse_ino_t inode, + struct fuse_file_info *fi) +{ + FuseExport *exp =3D fuse_req_userdata(req); + int ret; + + ret =3D blk_flush(exp->common.blk); + fuse_reply_err(req, ret < 0 ? -ret : 0); +} + static const struct fuse_lowlevel_ops fuse_ops =3D { + .lookup =3D fuse_lookup, + .getattr =3D fuse_getattr, + .setattr =3D fuse_setattr, + .open =3D fuse_open, + .read =3D fuse_read, + .write =3D fuse_write, + .flush =3D fuse_flush, }; =20 const BlockExportDriver blk_exp_fuse =3D { --=20 2.26.2