On 7/30/24 10:31, Sascha Hauer wrote:
> On Tue, Jul 30, 2024 at 09:19:20AM +0200, Ahmad Fatoum wrote:
>> Many managed flashes provide an erase operation, which need not be used
>> for regular writes, but is provided nonetheless for efficient clearing
>> of large regions of storage to a fixed bit pattern. The erase type allows
>> users to specify _why_ the erase operation is done, so the driver or
>> the core code can choose the most optimal operation.
>>
>> Existing code is annotated wither either ERASE_TO_WRITE for code that is
>
> s/wither/with/
>
>> immediately followed by a write and ERASE_TO_CLEAR for the standalone
>> erase operations of the shell and fastboot erase command.
>>
>> Use of an enum allows the future addition of more types, e.g.:
>>
>> ERASE_TO_ALL_ZERO: to efficiently implement android sparse all-ones
>> (like util-linux blkdiscard --zeroout)
>> ERASE_TO_ALL_ONE: to efficiently implement android sparse all-zeroes
>
> I suggest using ERASE_TO_ALL_ONE to implement sparse all-ones ;)
>
> Will fix both of these while applying in case there's nothing else in
> this series.
Thanks! :)
>
> Sascha
>
>> ERASE_TO_DISCARD: as alternative to ERASE_TO_CLEAR, when unwritten
>> regions are indeed allowed to have arbitrary content
>> (like util-linux blkdiscard without argument)
>> ERASE_TO_SECURE: erase data in a manner appropriate for wiping secrets
>> (like util-linux blkdiscard --secure)
>>
>> We don't introduce any functional change here yet, as no device yet sets
>> DEVFS_WRITE_AUTOERASE. This will follow in a separate commit.
>>
>> Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
>> ---
>> arch/arm/mach-imx/imx-bbu-external-nand.c | 2 +-
>> arch/arm/mach-imx/imx-bbu-internal.c | 4 ++--
>> arch/arm/mach-omap/am33xx_bbu_spi_mlo.c | 2 +-
>> commands/flash.c | 2 +-
>> commands/nandtest.c | 2 +-
>> common/bbu.c | 2 +-
>> common/environment.c | 7 ++++--
>> common/fastboot.c | 2 +-
>> common/state/backend_bucket_circular.c | 2 +-
>> drivers/misc/storage-by-uuid.c | 3 +++
>> drivers/usb/gadget/function/dfu.c | 4 ++--
>> fs/devfs-core.c | 7 +++++-
>> fs/devfs.c | 5 ++++-
>> fs/fs.c | 4 ++--
>> include/driver.h | 13 ++++++++++++
>> include/fs.h | 26 +++++++++++++++++++++--
>> lib/libfile.c | 2 +-
>> 17 files changed, 69 insertions(+), 20 deletions(-)
>>
>> diff --git a/arch/arm/mach-imx/imx-bbu-external-nand.c b/arch/arm/mach-imx/imx-bbu-external-nand.c
>> index 7523008cdb5a..72c2271ff37a 100644
>> --- a/arch/arm/mach-imx/imx-bbu-external-nand.c
>> +++ b/arch/arm/mach-imx/imx-bbu-external-nand.c
>> @@ -153,7 +153,7 @@ static int imx_bbu_external_nand_update(struct bbu_handler *handler, struct bbu_
>>
>> debug("writing %d bytes at 0x%08llx\n", now, nand_offset);
>>
>> - ret = erase(fd, blocksize, nand_offset);
>> + ret = erase(fd, blocksize, nand_offset, ERASE_TO_WRITE);
>> if (ret)
>> goto out;
>>
>> diff --git a/arch/arm/mach-imx/imx-bbu-internal.c b/arch/arm/mach-imx/imx-bbu-internal.c
>> index 8cdaab5c1676..4190d60d18dd 100644
>> --- a/arch/arm/mach-imx/imx-bbu-internal.c
>> +++ b/arch/arm/mach-imx/imx-bbu-internal.c
>> @@ -108,7 +108,7 @@ static int imx_bbu_write_device(struct imx_internal_bbu_handler *imx_handler,
>> if (imx_bbu_erase_required(imx_handler)) {
>> pr_debug("%s: erasing %s from 0x%08x to 0x%08x\n", __func__,
>> devicefile, offset, image_len);
>> - ret = erase(fd, image_len, offset);
>> + ret = erase(fd, image_len, offset, ERASE_TO_WRITE);
>> if (ret) {
>> pr_err("erasing %s failed with %s\n", devicefile,
>> strerror(-ret));
>> @@ -340,7 +340,7 @@ static int imx_bbu_internal_v2_write_nand_dbbt(struct imx_internal_bbu_handler *
>>
>> pr_debug("writing %d bytes at 0x%08llx\n", now, offset);
>>
>> - ret = erase(fd, blocksize, offset);
>> + ret = erase(fd, blocksize, offset, ERASE_TO_WRITE);
>> if (ret)
>> goto out;
>>
>> diff --git a/arch/arm/mach-omap/am33xx_bbu_spi_mlo.c b/arch/arm/mach-omap/am33xx_bbu_spi_mlo.c
>> index 2c58c9ae690e..951c3f8ce099 100644
>> --- a/arch/arm/mach-omap/am33xx_bbu_spi_mlo.c
>> +++ b/arch/arm/mach-omap/am33xx_bbu_spi_mlo.c
>> @@ -71,7 +71,7 @@ static int spi_nor_mlo_handler(struct bbu_handler *handler,
>> goto out;
>> }
>>
>> - ret = erase(dstfd, ERASE_SIZE_ALL, 0);
>> + ret = erase(dstfd, ERASE_SIZE_ALL, 0, ERASE_TO_WRITE);
>> if (ret < 0) {
>> printf("could not erase %s: %m", data->devicefile);
>> goto out1;
>> diff --git a/commands/flash.c b/commands/flash.c
>> index 5b7060aeadfb..de3bf65e5059 100644
>> --- a/commands/flash.c
>> +++ b/commands/flash.c
>> @@ -43,7 +43,7 @@ static int do_flerase(int argc, char *argv[])
>> goto out;
>> }
>>
>> - if (erase(fd, size, start)) {
>> + if (erase(fd, size, start, ERASE_TO_CLEAR)) {
>> perror("erase");
>> ret = 1;
>> }
>> diff --git a/commands/nandtest.c b/commands/nandtest.c
>> index ba7c87a32eea..bc138646a460 100644
>> --- a/commands/nandtest.c
>> +++ b/commands/nandtest.c
>> @@ -160,7 +160,7 @@ static int erase_and_write(loff_t ofs, unsigned char *data,
>> er.start = ofs;
>> er.length = meminfo.erasesize;
>>
>> - ret = erase(fd, er.length, er.start);
>> + ret = erase(fd, er.length, er.start, ERASE_TO_WRITE);
>> if (ret < 0) {
>> perror("\nerase");
>> printf("Could't not erase flash at 0x%08llx length 0x%08llx.\n",
>> diff --git a/common/bbu.c b/common/bbu.c
>> index f71747aa2f6d..9ea8a1a3f247 100644
>> --- a/common/bbu.c
>> +++ b/common/bbu.c
>> @@ -453,7 +453,7 @@ int bbu_std_file_handler(struct bbu_handler *handler,
>> goto err_close;
>> }
>>
>> - ret = erase(fd, data->len, 0);
>> + ret = erase(fd, data->len, 0, ERASE_TO_WRITE);
>> if (ret && ret != -ENOSYS) {
>> printf("erasing %s failed with %s\n", data->devicefile,
>> strerror(-ret));
>> diff --git a/common/environment.c b/common/environment.c
>> index 39cad0c16a77..dbf4c2f52365 100644
>> --- a/common/environment.c
>> +++ b/common/environment.c
>> @@ -152,7 +152,10 @@ static inline int protect(int fd, size_t count, unsigned long offset, int prot)
>> return 0;
>> }
>>
>> -static inline int erase(int fd, size_t count, unsigned long offset)
>> +enum erase_type {
>> + ERASE_TO_WRITE
>> +};
>> +static inline int erase(int fd, size_t count, unsigned long offset, enum erase_type type)
>> {
>> return 0;
>> }
>> @@ -380,7 +383,7 @@ int envfs_save(const char *filename, const char *dirname, unsigned flags)
>> goto out;
>> }
>>
>> - ret = erase(envfd, ERASE_SIZE_ALL, 0);
>> + ret = erase(envfd, ERASE_SIZE_ALL, 0, ERASE_TO_WRITE);
>>
>> /* ENOSYS and EOPNOTSUPP aren't errors here, many devices don't need it */
>> if (ret && errno != ENOSYS && errno != EOPNOTSUPP) {
>> diff --git a/common/fastboot.c b/common/fastboot.c
>> index f8a01dea7a65..d283fc8fc098 100644
>> --- a/common/fastboot.c
>> +++ b/common/fastboot.c
>> @@ -789,7 +789,7 @@ static void cb_erase(struct fastboot *fb, const char *cmd)
>> if (fd < 0)
>> fastboot_tx_print(fb, FASTBOOT_MSG_FAIL, strerror(-fd));
>>
>> - ret = erase(fd, ERASE_SIZE_ALL, 0);
>> + ret = erase(fd, ERASE_SIZE_ALL, 0, ERASE_TO_CLEAR);
>>
>> close(fd);
>>
>> diff --git a/common/state/backend_bucket_circular.c b/common/state/backend_bucket_circular.c
>> index 2ac5bf6a8218..6b5873aa9af1 100644
>> --- a/common/state/backend_bucket_circular.c
>> +++ b/common/state/backend_bucket_circular.c
>> @@ -220,7 +220,7 @@ static int state_mtd_peb_write(struct state_backend_storage_bucket_circular *cir
>> static int state_mtd_peb_erase(struct state_backend_storage_bucket_circular *circ)
>> {
>> return erase(circ->fd, circ->mtd->erasesize,
>> - (off_t)circ->eraseblock * circ->mtd->erasesize);
>> + (off_t)circ->eraseblock * circ->mtd->erasesize, ERASE_TO_WRITE);
>> }
>> #endif
>>
>> diff --git a/drivers/misc/storage-by-uuid.c b/drivers/misc/storage-by-uuid.c
>> index db15b64d7dcf..8b8fd901685e 100644
>> --- a/drivers/misc/storage-by-uuid.c
>> +++ b/drivers/misc/storage-by-uuid.c
>> @@ -126,6 +126,9 @@ static void storage_by_uuid_add_partitions(struct sbu *sbu, struct cdev *rcdev)
>> sbu->cdev.dev = sbu->dev;
>> sbu->cdev.priv = sbu;
>>
>> + if (rcdev->flags & DEVFS_WRITE_AUTOERASE)
>> + sbu->cdev.flags |= DEVFS_WRITE_AUTOERASE;
>> +
>> ret = devfs_create(&sbu->cdev);
>> if (ret) {
>> dev_err(sbu->dev, "Failed to create cdev: %s\n", strerror(-ret));
>> diff --git a/drivers/usb/gadget/function/dfu.c b/drivers/usb/gadget/function/dfu.c
>> index a41ff22dcebc..208e0cd23c29 100644
>> --- a/drivers/usb/gadget/function/dfu.c
>> +++ b/drivers/usb/gadget/function/dfu.c
>> @@ -208,7 +208,7 @@ static void dfu_do_write(struct dfu_work *dw)
>>
>> if (prog_erase && (dfu_written + wlen) > dfu_erased) {
>> size = roundup(wlen, dfu_mtdinfo.erasesize);
>> - ret = erase(dfufd, size, dfu_erased);
>> + ret = erase(dfufd, size, dfu_erased, ERASE_TO_WRITE);
>> dfu_erased += size;
>> if (ret && ret != -ENOSYS) {
>> perror("erase");
>> @@ -333,7 +333,7 @@ static void dfu_do_copy(struct dfu_work *dw)
>> return;
>> }
>>
>> - ret = erase(fd, ERASE_SIZE_ALL, 0);
>> + ret = erase_flash(fd, ERASE_SIZE_ALL, 0);
>> close(fd);
>> if (ret && ret != -ENOSYS) {
>> perror("erase");
>> diff --git a/fs/devfs-core.c b/fs/devfs-core.c
>> index ed445fbd4712..2715193c6956 100644
>> --- a/fs/devfs-core.c
>> +++ b/fs/devfs-core.c
>> @@ -509,6 +509,7 @@ static struct cdev *__devfs_add_partition(struct cdev *cdev,
>> loff_t _end = end ? *end : 0;
>> static struct cdev *new;
>> struct cdev *overlap;
>> + unsigned inherited_flags = 0;
>>
>> if (cdev_by_name(partinfo->name))
>> return ERR_PTR(-EEXIST);
>> @@ -551,11 +552,14 @@ static struct cdev *__devfs_add_partition(struct cdev *cdev,
>> return overlap;
>> }
>>
>> + /* Filter flags that we want to pass along to children */
>> + inherited_flags |= cdev->flags & DEVFS_WRITE_AUTOERASE;
>> +
>> if (IS_ENABLED(CONFIG_MTD) && cdev->mtd) {
>> struct mtd_info *mtd;
>>
>> mtd = mtd_add_partition(cdev->mtd, offset, size,
>> - partinfo->flags, partinfo->name);
>> + partinfo->flags | inherited_flags, partinfo->name);
>> if (IS_ERR(mtd))
>> return (void *)mtd;
>>
>> @@ -571,6 +575,7 @@ static struct cdev *__devfs_add_partition(struct cdev *cdev,
>> new->priv = cdev->priv;
>> new->size = size;
>> new->offset = cdev->offset + offset;
>> + new->flags = inherited_flags;
>>
>> new->dev = cdev->dev;
>> new->master = cdev;
>> diff --git a/fs/devfs.c b/fs/devfs.c
>> index 9dbfa91b1d9f..5feb76cfef86 100644
>> --- a/fs/devfs.c
>> +++ b/fs/devfs.c
>> @@ -61,13 +61,16 @@ static int devfs_lseek(struct device *_dev, FILE *f, loff_t pos)
>> }
>>
>> static int devfs_erase(struct device *_dev, FILE *f, loff_t count,
>> - loff_t offset)
>> + loff_t offset, enum erase_type type)
>> {
>> struct cdev *cdev = f->priv;
>>
>> if (cdev->flags & DEVFS_PARTITION_READONLY)
>> return -EPERM;
>>
>> + if ((type == ERASE_TO_WRITE) && (cdev->flags & DEVFS_WRITE_AUTOERASE))
>> + return 0;
>> +
>> if (count + offset > cdev->size)
>> count = cdev->size - offset;
>>
>> diff --git a/fs/fs.c b/fs/fs.c
>> index 656434f67ffa..5e7e05f4990a 100644
>> --- a/fs/fs.c
>> +++ b/fs/fs.c
>> @@ -600,7 +600,7 @@ loff_t lseek(int fd, loff_t offset, int whence)
>> }
>> EXPORT_SYMBOL(lseek);
>>
>> -int erase(int fd, loff_t count, loff_t offset)
>> +int erase(int fd, loff_t count, loff_t offset, enum erase_type type)
>> {
>> struct fs_driver *fsdrv;
>> FILE *f = fd_to_file(fd, false);
>> @@ -621,7 +621,7 @@ int erase(int fd, loff_t count, loff_t offset)
>> assert_command_context();
>>
>> if (fsdrv->erase)
>> - ret = fsdrv->erase(&f->fsdev->dev, f, count, offset);
>> + ret = fsdrv->erase(&f->fsdev->dev, f, count, offset, type);
>> else
>> ret = -ENOSYS;
>>
>> diff --git a/include/driver.h b/include/driver.h
>> index 2b4db2221a6c..c4067d531cc7 100644
>> --- a/include/driver.h
>> +++ b/include/driver.h
>> @@ -562,6 +562,19 @@ extern struct list_head cdev_list;
>> #define DEVFS_PARTITION_BOOTABLE_LEGACY (1U << 11)
>> #define DEVFS_PARTITION_BOOTABLE_ESP (1U << 12)
>> #define DEVFS_PARTITION_FOR_FIXUP (1U << 13)
>> +#define DEVFS_WRITE_AUTOERASE (1U << 14)
>> +
>> +/**
>> + * cdev_write_requires_erase - Check whether writes must be done to erased blocks
>> + * @cdev: pointer to cdev structure
>> + *
>> + * This function checks if the erase operation is required, so a subsequent
>> + * write operation can write all bits.
>> + */
>> +static inline bool cdev_write_requires_erase(const struct cdev *cdev)
>> +{
>> + return !(cdev->flags & DEVFS_WRITE_AUTOERASE);
>> +}
>>
>> static inline bool cdev_is_mbr_partitioned(const struct cdev *master)
>> {
>> diff --git a/include/fs.h b/include/fs.h
>> index f87c4c40273f..f5950a052923 100644
>> --- a/include/fs.h
>> +++ b/include/fs.h
>> @@ -10,6 +10,7 @@
>> #include <sys/stat.h>
>> #include <driver.h>
>> #include <filetype.h>
>> +#include <linux/bits.h>
>> #include <linux/fs.h>
>> #include <linux/string.h>
>> #include <linux/limits.h>
>> @@ -38,6 +39,27 @@ typedef struct filep {
>>
>> #define FS_DRIVER_NO_DEV 1
>>
>> +/**
>> + * enum erase_type - Type of erase operation
>> + * @ERASE_TO_WRITE: Conduct low-level erase operation to prepare for a write
>> + * to all or part of the erased regions. This is required
>> + * for raw flashes, but can be omitted by flashes behind
>> + * a FTL that autoerases on write (e.g. eMMCs)
>> + * @ERASE_TO_CLEAR: Force an erase of the region. When read afterwards,
>> + * A fixed pattern should result, usually either all-zeroes
>> + * or all-ones depending on storage technology.
>> + *
>> + * Many managed flashes provide an erase operation, which need not be used
>> + * for regular writes, but is provided nonetheless for efficient clearing
>> + * of large regions of storage to a fixed bit pattern. The erase type allows
>> + * users to specify _why_ the erase operation is done, so the driver or
>> + * the core code can choose the most optimal operation.
>> + */
>> +enum erase_type {
>> + ERASE_TO_WRITE,
>> + ERASE_TO_CLEAR
>> +};
>> +
>> struct fs_driver {
>> int (*probe) (struct device *dev);
>>
>> @@ -58,7 +80,7 @@ struct fs_driver {
>>
>> int (*ioctl)(struct device *dev, FILE *f, unsigned int request, void *buf);
>> int (*erase)(struct device *dev, FILE *f, loff_t count,
>> - loff_t offset);
>> + loff_t offset, enum erase_type type);
>> int (*protect)(struct device *dev, FILE *f, size_t count,
>> loff_t offset, int prot);
>> int (*discard_range)(struct device *dev, FILE *f, loff_t count,
>> @@ -127,7 +149,7 @@ int umount_by_cdev(struct cdev *cdev);
>>
>> /* not-so-standard functions */
>> #define ERASE_SIZE_ALL ((loff_t) - 1)
>> -int erase(int fd, loff_t count, loff_t offset);
>> +int erase(int fd, loff_t count, loff_t offset, enum erase_type type);
>> int protect(int fd, size_t count, loff_t offset, int prot);
>> int discard_range(int fd, loff_t count, loff_t offset);
>> int protect_file(const char *file, int prot);
>> diff --git a/lib/libfile.c b/lib/libfile.c
>> index a34e011f4f7c..80d4591dd6e5 100644
>> --- a/lib/libfile.c
>> +++ b/lib/libfile.c
>> @@ -412,7 +412,7 @@ int write_file_flash(const char *filename, const void *buf, size_t size)
>> if (fd < 0)
>> return fd;
>>
>> - ret = erase(fd, size, 0);
>> + ret = erase(fd, size, 0, ERASE_TO_WRITE);
>> if (ret < 0)
>> goto out_close;
>>
>> --
>> 2.39.2
>>
>>
>>
>
