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s390/dasd: Stamp a format label into newly formatted volumes
When a CDL volume is formatted, write a small on-disk label so the format can later be recognised by the kernel. The next patch will use this for ESE detection. The label records a magic, a version, whether the volume is ESE, and whether it was formatted quick (space released, thin) or full. It lives in track 0, head 0, record 4 (the first non-special CDL record). R4 is written by the same channel program that formats track 0 - its WRITE_CKD transfers count + the label data instead of count-only - so label and track format reach the disk atomically; a valid magic then marks a completed format without a separate, racy write. Quick vs full is derived from a full space release (RAS) preceding the format: dasd_eckd_release_space_full() sets a per-device flag the next format consumes. Non-ESE volumes and formats without a preceding full release are recorded as full. struct dasd_format_label is exactly 512 bytes (the smallest block size) so it fits one record; larger blocks zero-pad the rest. Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com> Signed-off-by: Stefan Haberland <sth@linux.ibm.com> Link: https://patch.msgid.link/20260805111612.1285190-16-sth@linux.ibm.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Stefan Haberland
committed by
Jens Axboe
Jens Axboe
parent
4e304b2e56
commit
7d206efdc2
@@ -19,6 +19,7 @@
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#include <linux/init.h>
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#include <linux/seq_file.h>
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#include <linux/uaccess.h>
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#include <linux/utsname.h>
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#include <linux/io.h>
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#include <asm/css_chars.h>
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@@ -2722,6 +2723,28 @@ dasd_eckd_build_check(struct dasd_device *base, struct format_data_t *fdata,
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return cqr;
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}
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/* Fill the format label into a R4 record buffer, zero-padded to blksize. */
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static void dasd_eckd_fill_format_label(struct dasd_device *device, void *data,
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unsigned int blksize)
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{
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struct dasd_eckd_private *private = device->private;
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struct dasd_format_label *label = data;
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memset(label, 0, blksize);
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label->magic = DASD_ESE_LABEL_MAGIC;
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label->version = DASD_ESE_LABEL_VERSION;
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if (dasd_eckd_is_ese(device))
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label->flags |= DASD_ESE_LABEL_F_ESE;
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if (private->ese_format_quick)
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label->flags |= DASD_ESE_LABEL_F_QUICK;
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else
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label->flags |= DASD_ESE_LABEL_F_FULL;
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label->blksize = blksize;
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label->format_tod = get_tod_clock();
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strscpy(label->kernel_version, init_utsname()->release,
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sizeof(label->kernel_version));
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}
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static struct dasd_ccw_req *
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dasd_eckd_build_format(struct dasd_device *base, struct dasd_device *startdev,
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struct format_data_t *fdata, int enable_pav)
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@@ -2740,6 +2763,7 @@ dasd_eckd_build_format(struct dasd_device *base, struct dasd_device *startdev,
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int r0_perm;
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int nr_tracks;
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int use_prefix;
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int write_label;
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if (enable_pav)
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startdev = dasd_alias_get_start_dev(base);
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@@ -2773,6 +2797,15 @@ dasd_eckd_build_format(struct dasd_device *base, struct dasd_device *startdev,
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use_prefix = base_priv->features.feature[8] & 0x01;
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/*
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* Stamp the format label into R4 of the very first track. Only for CDL
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* (R4 is the first non-special record there), only when this request
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* covers track 0, only for the record-writing format intensities (not
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* track invalidation), and only if the track actually has an R4.
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*/
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write_label = (intensity & 0x08) && !((intensity & ~0x08) & 0x04) &&
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fdata->start_unit == 0 && rpt > 3;
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switch (intensity) {
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case 0x00: /* Normal format */
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case 0x08: /* Normal format, use cdl. */
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@@ -2819,6 +2852,10 @@ dasd_eckd_build_format(struct dasd_device *base, struct dasd_device *startdev,
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return ERR_PTR(-EINVAL);
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}
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/* room for the label data that R4 carries in addition to its count */
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if (write_label)
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datasize += fdata->blksize;
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fcp = dasd_fmalloc_request(DASD_ECKD_MAGIC, cplength, datasize, startdev);
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if (IS_ERR(fcp))
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return fcp;
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@@ -2963,7 +3000,21 @@ dasd_eckd_build_format(struct dasd_device *base, struct dasd_device *startdev,
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ccw->cmd_code =
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DASD_ECKD_CCW_WRITE_CKD_MT;
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ccw->flags = CCW_FLAG_SLI;
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ccw->count = 8;
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if (write_label && address.cyl == 0 &&
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address.head == 0 && i == 3) {
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/*
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* R4 carries the label as its record
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* data; it follows ect contiguously so
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* the CCW transfers count + data.
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*/
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dasd_eckd_fill_format_label(base,
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data,
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fdata->blksize);
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data += fdata->blksize;
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ccw->count = 8 + fdata->blksize;
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} else {
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ccw->count = 8;
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}
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ccw->cda = virt_to_dma32(ect);
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ccw++;
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}
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@@ -3173,6 +3224,9 @@ static int dasd_eckd_format_process_data(struct dasd_device *base,
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static int dasd_eckd_format_device(struct dasd_device *base,
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struct format_data_t *fdata, int enable_pav)
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{
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struct dasd_eckd_private *private = base->private;
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int rc;
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/*
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* A full format (start_unit == 0) returns the device to a fully sparse
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* state, so restart the heuristic from ft1 without an offline cycle.
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@@ -3180,8 +3234,18 @@ static int dasd_eckd_format_device(struct dasd_device *base,
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if (fdata->start_unit == 0)
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dasd_ft_bias_apply(base);
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return dasd_eckd_format_process_data(base, fdata, enable_pav, 0, NULL,
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0, NULL);
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rc = dasd_eckd_format_process_data(base, fdata, enable_pav, 0, NULL,
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0, NULL);
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/*
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* The quick-format indicator was consumed by the label stamped into
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* track 0; clear it so a later format that is not preceded by a full
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* space release is recorded as a full format.
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*/
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if (fdata->start_unit == 0)
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private->ese_format_quick = 0;
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return rc;
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}
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static bool test_and_set_format_track(sector_t start, sector_t end,
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@@ -4082,6 +4146,7 @@ dasd_eckd_dso_ras(struct dasd_device *device, struct dasd_block *block,
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static int dasd_eckd_release_space_full(struct dasd_device *device)
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{
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struct dasd_eckd_private *private;
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struct dasd_ccw_req *cqr;
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int rc;
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@@ -4093,10 +4158,16 @@ static int dasd_eckd_release_space_full(struct dasd_device *device)
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if (!rc) {
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/*
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* Releasing all space (RAS) wipes every track and the device is fully
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* sparse again, so restart the heuristic from ft1.
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* Releasing all space (RAS) wipes every track and the device is
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* fully sparse again, so restart the heuristic from ft1.
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*/
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dasd_ft_bias_apply(device);
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/*
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* A full release is what makes a subsequent format a quick
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* (thin) one; remember it so the format label records that.
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*/
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private = device->private;
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private->ese_format_quick = 1;
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}
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dasd_sfree_request(cqr, cqr->memdev);
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@@ -159,6 +159,39 @@ struct eckd_r0 {
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#define DASD_EAV_CYL_HI_SHIFT 16 /* cylinder bits beyond the 16-bit cyl field */
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#define DASD_EAV_HEAD_HI_SHIFT 4 /* head occupies the low-order 4 bits of head */
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/*
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* On-disk DASD format label.
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*
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* Written into track 0, head 0, record 4 (R4 - the first non-special CDL
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* record) as part of the same channel program that formats track 0, so it is
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* stored atomically with the track: either both the track format and the label
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* make it to disk or neither does. Its presence with a valid magic therefore
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* marks a completed format and can be used for format detection.
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*
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* The structure is exactly the smallest supported block size (512 bytes) so it
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* always fits into a single record.
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* For larger block sizes the rest of the record is zero padded.
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* The magic together with the version is used to recognise a valid label.
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*/
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#define DASD_ESE_LABEL_MAGIC 0xC4C1E2C4C6D4E3F1ULL /* EBCDIC "DASDFMT1" */
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#define DASD_ESE_LABEL_VERSION 1
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/* dasd_format_label.flags */
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#define DASD_ESE_LABEL_F_ESE 0x00000001 /* volume is extent space efficient */
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#define DASD_ESE_LABEL_F_QUICK 0x00000002 /* quick (space released) format */
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#define DASD_ESE_LABEL_F_FULL 0x00000004 /* full format */
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struct dasd_format_label {
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__u64 magic; /* DASD_ESE_LABEL_MAGIC */
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__u32 version; /* DASD_ESE_LABEL_VERSION */
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__u32 flags; /* DASD_ESE_LABEL_F_* */
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__u32 blksize; /* block size the volume was formatted with */
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__u32 reserved0;
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__u64 format_tod; /* TOD clock at format time */
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__u8 kernel_version[64]; /* NUL terminated kernel release (uname -r) */
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__u8 reserved[416]; /* pad the struct to 512 bytes */
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} __packed;
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struct ch_t {
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__u16 cyl;
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__u16 head;
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@@ -709,6 +742,11 @@ struct dasd_eckd_private {
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u32 fcx_max_data;
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char suc_reason;
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/*
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* Set when the whole volume's space was released (full RAS); consumed by
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* the next format to mark the on-disk label as a quick (vs full) format.
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*/
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int ese_format_quick;
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};
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