diff options
| -rw-r--r-- | libbb/Config.src | 22 | ||||
| -rw-r--r-- | libbb/loop.c | 52 |
2 files changed, 65 insertions, 9 deletions
diff --git a/libbb/Config.src b/libbb/Config.src index 66a3ffa..b980f19 100644 --- a/libbb/Config.src +++ b/libbb/Config.src @@ -369,3 +369,25 @@ config UNICODE_PRESERVE_BROKEN For example, this means that entering 'l', 's', ' ', 0xff, [Enter] at shell prompt will list file named 0xff (single char name with char value 255), not file named '?'. + +choice + prompt "Use LOOP_CONFIGURE for losetup and loop mounts" + default TRY_LOOP_CONFIGURE + help + LOOP_CONFIGURE is added to Linux 5.8 + https://lwn.net/Articles/820408/ + This allows userspace to completely setup a loop device with a single + ioctl, removing the in-between state where the device can be partially + configured - eg the loop device has a backing file associated with it, + but is reading from the wrong offset. + +config LOOP_CONFIGURE + bool "use LOOP_CONFIGURE, needs kernel >= 5.8" + +config NO_LOOP_CONFIGURE + bool "use LOOP_SET_FD + LOOP_SET_STATUS" + +config TRY_LOOP_CONFIGURE + bool "try LOOP_CONFIGURE, fall back to LOOP_SET_FD + LOOP_SET_STATUS" + +endchoice diff --git a/libbb/loop.c b/libbb/loop.c index 424c392..e930b1b 100644 --- a/libbb/loop.c +++ b/libbb/loop.c @@ -110,26 +110,39 @@ static int get_next_free_loop(char *dev, int id) return loopdevno; } -static int set_loopdev_params(int ffd, - int lfd, const char *file, +#if ENABLE_TRY_LOOP_CONFIGURE || ENABLE_LOOP_CONFIGURE +# define LOOP_CONFIGURE 0x4C0A +struct loop_config { + uint32_t fd; + uint32_t block_size; + struct loop_info64 info; + uint64_t __reserved[8]; +}; +#endif + +static int set_loopdev_params(int lfd, + int ffd, const char *file, unsigned long long offset, unsigned long long sizelimit, unsigned flags) { int rc; +#if ENABLE_TRY_LOOP_CONFIGURE || ENABLE_LOOP_CONFIGURE + struct loop_config lconfig; +# define loopinfo lconfig.info +#else bb_loop_info loopinfo; +#endif rc = ioctl(lfd, BB_LOOP_GET_STATUS, &loopinfo); /* If device is free, try to claim it */ if (rc && errno == ENXIO) { - /* Associate free loop device with file */ - rc = ioctl(lfd, LOOP_SET_FD, ffd); - if (rc != 0) { - /* Ouch... race: the device already has a fd */ - return -1; - } +#if ENABLE_TRY_LOOP_CONFIGURE || ENABLE_LOOP_CONFIGURE + memset(&lconfig, 0, sizeof(lconfig)); +#else memset(&loopinfo, 0, sizeof(loopinfo)); +#endif safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE); loopinfo.lo_offset = offset; loopinfo.lo_sizelimit = sizelimit; @@ -140,6 +153,25 @@ static int set_loopdev_params(int ffd, * is wrong (would free the loop device!) */ loopinfo.lo_flags = (flags & ~BB_LO_FLAGS_READ_ONLY); + +#if ENABLE_TRY_LOOP_CONFIGURE || ENABLE_LOOP_CONFIGURE + lconfig.fd = ffd; + rc = ioctl(lfd, LOOP_CONFIGURE, &lconfig); + if (rc == 0) + return rc; /* SUCCESS! */ +# if ENABLE_TRY_LOOP_CONFIGURE + if (errno != EINVAL) + return rc; /* error other than old kernel */ + /* Old kernel, fall through into old way to do it: */ +# endif +#endif +#if ENABLE_TRY_LOOP_CONFIGURE || ENABLE_NO_LOOP_CONFIGURE + /* Associate free loop device with file */ + rc = ioctl(lfd, LOOP_SET_FD, ffd); + if (rc != 0) { + /* Ouch... race: the device already has a fd */ + return rc; + } rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo); if (rc != 0 && (loopinfo.lo_flags & BB_LO_FLAGS_AUTOCLEAR)) { /* Old kernel, does not support LO_FLAGS_AUTOCLEAR? */ @@ -151,8 +183,10 @@ static int set_loopdev_params(int ffd, return rc; /* SUCCESS! */ /* failure, undo LOOP_SET_FD */ ioctl(lfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary +#endif } return -1; +#undef loopinfo } /* Returns opened fd to the loop device, <0 on error. @@ -227,7 +261,7 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse goto try_next_loopN; } - rc = set_loopdev_params(ffd, lfd, file, offset, sizelimit, flags); + rc = set_loopdev_params(lfd, ffd, file, offset, sizelimit, flags); if (rc == 0) { /* SUCCESS! */ if (!*device) |