Add failfast support.

Allow per-device "failfast" flag to be set when creating an
array or adding devices to an array.

When re-adding a device which had the failfast flag, it can be removed
using --nofailfast.

failfast status is printed in --detail and --examine output.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>

diff --git a/Create.c b/Create.c
index 1594a39191396c315c036c4adaec5de72ac18bf1..bd114eabafc14e5f8864cb9d06ab0285c1c77c19 100644 (file)
--- a/Create.c
+++ b/Create.c
@@ -890,6 +890,8 @@ int Create(struct supertype *st, char *mddev,
 
                                if (dv->writemostly == 1)
                                        inf->disk.state |= (1<<MD_DISK_WRITEMOSTLY);
+                               if (dv->failfast == 1)
+                                       inf->disk.state |= (1<<MD_DISK_FAILFAST);
 
                                if (have_container)
                                        fd = -1;

diff --git a/Detail.c b/Detail.c
index 925e4794c983785698d1648a80d5e6b49fb2d956..509b0d41876843b7c3d96be965526867c7b66aae 100644 (file)
--- a/Detail.c
+++ b/Detail.c
@@ -658,6 +658,7 @@ This is pretty boring
                        }
                        if (disk.state & (1<<MD_DISK_REMOVED)) printf(" removed");
                        if (disk.state & (1<<MD_DISK_WRITEMOSTLY)) printf(" writemostly");
+                       if (disk.state & (1<<MD_DISK_FAILFAST)) printf(" failfast");
                        if (disk.state & (1<<MD_DISK_JOURNAL)) printf(" journal");
                        if ((disk.state &
                             ((1<<MD_DISK_ACTIVE)|(1<<MD_DISK_SYNC)

diff --git a/Incremental.c b/Incremental.c
index cc01d41e641af8c46fc151594cd6628daafad206..75d95ccc497a4a3c7fcb364b15a71cc9478b6238 100644 (file)
--- a/Incremental.c
+++ b/Incremental.c
@@ -1035,6 +1035,7 @@ static int array_try_spare(char *devname, int *dfdp, struct dev_policy *pol,
                        devlist.next = NULL;
                        devlist.used = 0;
                        devlist.writemostly = 0;
+                       devlist.failfast = 0;
                        devlist.devname = chosen_devname;
                        sprintf(chosen_devname, "%d:%d", major(stb.st_rdev),
                                minor(stb.st_rdev));

diff --git a/Manage.c b/Manage.c
index 1b7b0c111c837a01e084114840d4969d54601121..429d8631cd23a2efc2d18c2388395d5b34ef3951 100644 (file)
--- a/Manage.c
+++ b/Manage.c
@@ -683,8 +683,13 @@ int attempt_re_add(int fd, int tfd, struct mddev_dev *dv,
                        disc.state |= 1 << MD_DISK_WRITEMOSTLY;
                if (dv->writemostly == 2)
                        disc.state &= ~(1 << MD_DISK_WRITEMOSTLY);
+               if (dv->failfast == 1)
+                       disc.state |= 1 << MD_DISK_FAILFAST;
+               if (dv->failfast == 2)
+                       disc.state &= ~(1 << MD_DISK_FAILFAST);
                remove_partitions(tfd);
-               if (update || dv->writemostly > 0) {
+               if (update || dv->writemostly > 0
+                       || dv->failfast > 0) {
                        int rv = -1;
                        tfd = dev_open(dv->devname, O_RDWR);
                        if (tfd < 0) {
@@ -700,6 +705,14 @@ int attempt_re_add(int fd, int tfd, struct mddev_dev *dv,
                                rv = dev_st->ss->update_super(
                                        dev_st, NULL, "readwrite",
                                        devname, verbose, 0, NULL);
+                       if (dv->failfast == 1)
+                               rv = dev_st->ss->update_super(
+                                       dev_st, NULL, "failfast",
+                                       devname, verbose, 0, NULL);
+                       if (dv->failfast == 2)
+                               rv = dev_st->ss->update_super(
+                                       dev_st, NULL, "nofailfast",
+                                       devname, verbose, 0, NULL);
                        if (update)
                                rv = dev_st->ss->update_super(
                                        dev_st, NULL, update,
@@ -964,6 +977,8 @@ int Manage_add(int fd, int tfd, struct mddev_dev *dv,
                        disc.state |= (1 << MD_DISK_JOURNAL) | (1 << MD_DISK_SYNC);
                if (dv->writemostly == 1)
                        disc.state |= 1 << MD_DISK_WRITEMOSTLY;
+               if (dv->failfast == 1)
+                       disc.state |= 1 << MD_DISK_FAILFAST;
                dfd = dev_open(dv->devname, O_RDWR | O_EXCL|O_DIRECT);
                if (tst->ss->add_to_super(tst, &disc, dfd,
                                          dv->devname, INVALID_SECTORS))
@@ -1009,6 +1024,8 @@ int Manage_add(int fd, int tfd, struct mddev_dev *dv,
 
        if (dv->writemostly == 1)
                disc.state |= (1 << MD_DISK_WRITEMOSTLY);
+       if (dv->failfast == 1)
+               disc.state |= (1 << MD_DISK_FAILFAST);
        if (tst->ss->external) {
                /* add a disk
                 * to an external metadata container */
@@ -1785,6 +1802,7 @@ int move_spare(char *from_devname, char *to_devname, dev_t devid)
        devlist.next = NULL;
        devlist.used = 0;
        devlist.writemostly = 0;
+       devlist.failfast = 0;
        devlist.devname = devname;
        sprintf(devname, "%d:%d", major(devid), minor(devid));
 

diff --git a/ReadMe.c b/ReadMe.c
index d3fcb6132fe97f24292aef9c6c1faf3d3339e9c0..8da49ef46dfbf0abf86040a1e8098bad17eb201e 100644 (file)
--- a/ReadMe.c
+++ b/ReadMe.c
@@ -136,6 +136,8 @@ struct option long_options[] = {
     {"bitmap-chunk", 1, 0, BitmapChunk},
     {"write-behind", 2, 0, WriteBehind},
     {"write-mostly",0, 0, WriteMostly},
+    {"failfast",  0, 0,  FailFast},
+    {"nofailfast",0, 0,  NoFailFast},
     {"re-add",    0, 0,  ReAdd},
     {"homehost",  1, 0,  HomeHost},
     {"symlinks",  1, 0,  Symlinks},

diff --git a/md.4 b/md.4
index f1b88ee6bb03ee462d2a832b4ab760964539a9fe..5bdf7a7bd37565b59f518bef2d358474f9ed4326 100644 (file)
--- a/md.4
+++ b/md.4
@@ -916,6 +916,60 @@ slow).  The extra latency of the remote link will not slow down normal
 operations, but the remote system will still have a reasonably
 up-to-date copy of all data.
 
+.SS FAILFAST
+
+From Linux 4.10,
+.I
+md
+supports FAILFAST for RAID1 and RAID10 arrays.  This is a flag that
+can be set on individual drives, though it is usually set on all
+drives, or no drives.
+
+When
+.I md
+sends an I/O request to a drive that is marked as FAILFAST, and when
+the array could survive the loss of that drive without losing data,
+.I md
+will request that the underlying device does not perform any retries.
+This means that a failure will be reported to
+.I md
+promptly, and it can mark the device as faulty and continue using the
+other device(s).
+.I md
+cannot control the timeout that the underlying devices use to
+determine failure.  Any changes desired to that timeout must be set
+explictly on the underlying device, separately from using
+.IR mdadm .
+
+If a FAILFAST request does fail, and if it is still safe to mark the
+device as faulty without data loss, that will be done and the array
+will continue functioning on a reduced number of devices.  If it is not
+possible to safely mark the device as faulty,
+.I md
+will retry the request without disabling retries in the underlying
+device.  In any case,
+.I md
+will not attempt to repair read errors on a device marked as FAILFAST
+by writing out the correct.  It will just mark the device as faulty.
+
+FAILFAST is appropriate for storage arrays that have a low probability
+of true failure, but will sometimes introduce unacceptable delays to
+I/O requests while performing internal maintenance.  The value of
+setting FAILFAST involves a trade-off.  The gain is that the chance of
+unacceptable delays is substantially reduced.  The cost is that the
+unlikely event of data-loss on one device is slightly more likely to
+result in data-loss for the array.
+
+When a device in an array using FAILFAST is marked as faulty, it will
+usually become usable again in a short while.
+.I mdadm
+makes no attempt to detect that possibility.  Some separate
+mechanism, tuned to the specific details of the expected failure modes,
+needs to be created to monitor devices to see when they return to full
+functionality, and to then re-add them to the array.  In order of
+this "re-add" functionality to be effective, an array using FAILFAST
+should always have a write-intent bitmap.
+
 .SS RESTRIPING
 
 .IR Restriping ,

diff --git a/md_p.h b/md_p.h
index 0d691fbc987dc3bd9a0845a8c63d7af40cd925c7..dc9fec165cb657c1f93e709a5c2267d5d242ac60 100644 (file)
--- a/md_p.h
+++ b/md_p.h
@@ -89,6 +89,7 @@
                                   * read requests will only be sent here in
                                   * dire need
                                   */
+#define        MD_DISK_FAILFAST        10 /* Fewer retries, more failures */
 
 #define MD_DISK_REPLACEMENT    17
 #define MD_DISK_JOURNAL                18 /* disk is used as the write journal in RAID-5/6 */

diff --git a/mdadm.8.in b/mdadm.8.in
index 3c0c58f95f35680ad1dcc79a591ae2df5a4f82d2..aa80f0c1a631bfd6428a7ec812a4b34d5b831786 100644 (file)
--- a/mdadm.8.in
+++ b/mdadm.8.in
@@ -747,7 +747,7 @@ subsequent devices listed in a
 .BR \-\-create ,
 or
 .B \-\-add
-command will be flagged as 'write-mostly'.  This is valid for RAID1
+command will be flagged as 'write\-mostly'.  This is valid for RAID1
 only and means that the 'md' driver will avoid reading from these
 devices if at all possible.  This can be useful if mirroring over a
 slow link.
@@ -761,6 +761,25 @@ A write-intent bitmap is required in order to use write-behind
 mode, and write-behind is only attempted on drives marked as
 .IR write-mostly .
 
+.TP
+.BR \-\-failfast
+subsequent devices listed in a
+.B \-\-create
+or
+.B \-\-add
+command will be flagged as  'failfast'.  This is valid for RAID1 and
+RAID10 only.  IO requests to these devices will be encouraged to fail
+quickly rather than cause long delays due to error handling.  Also no
+attempt is made to repair a read error on these devices.
+
+If an array becomes degraded so that the 'failfast' device is the only
+usable device, the 'failfast' flag will then be ignored and extended
+delays will be preferred to complete failure.
+
+The 'failfast' flag is appropriate for storage arrays which have a
+low probability of true failure, but which may sometimes
+cause unacceptable delays due to internal maintenance functions.
+
 .TP
 .BR \-\-assume\-clean
 Tell
@@ -1452,6 +1471,17 @@ that had a failed journal. To avoid interrupting on-going write opertions,
 .B \-\-add-journal
 only works for array in Read-Only state.
 
+.TP
+.BR \-\-failfast
+Subsequent devices that are added or re\-added will have
+the 'failfast' flag set.  This is only valid for RAID1 and RAID10 and
+means that the 'md' driver will avoid long timeouts on error handling
+where possible.
+.TP
+.BR \-\-nofailfast
+Subsequent devices that are re\-added will be re\-added without
+the 'failfast' flag set.
+
 .P
 Each of these options requires that the first device listed is the array
 to be acted upon, and the remainder are component devices to be added,

diff --git a/mdadm.c b/mdadm.c
index cca093318d8d2d5f81e09188f624e06a575e2fba..3c8f273c82546bd7c00eb269ac973fbdd054bc22 100644 (file)
--- a/mdadm.c
+++ b/mdadm.c
@@ -90,6 +90,7 @@ int main(int argc, char *argv[])
        int spare_sharing = 1;
        struct supertype *ss = NULL;
        int writemostly = 0;
+       int failfast = 0;
        char *shortopt = short_options;
        int dosyslog = 0;
        int rebuild_map = 0;
@@ -295,6 +296,7 @@ int main(int argc, char *argv[])
                                        dv->devname = optarg;
                                        dv->disposition = devmode;
                                        dv->writemostly = writemostly;
+                                       dv->failfast = failfast;
                                        dv->used = 0;
                                        dv->next = NULL;
                                        *devlistend = dv;
@@ -351,6 +353,7 @@ int main(int argc, char *argv[])
                        dv->devname = optarg;
                        dv->disposition = devmode;
                        dv->writemostly = writemostly;
+                       dv->failfast = failfast;
                        dv->used = 0;
                        dv->next = NULL;
                        *devlistend = dv;
@@ -417,6 +420,14 @@ int main(int argc, char *argv[])
                        writemostly = 2;
                        continue;
 
+               case O(MANAGE,FailFast):
+               case O(CREATE,FailFast):
+                       failfast = 1;
+                       continue;
+               case O(MANAGE,NoFailFast):
+                       failfast = 2;
+                       continue;
+
                case O(GROW,'z'):
                case O(CREATE,'z'):
                case O(BUILD,'z'): /* size */

diff --git a/mdadm.h b/mdadm.h
old mode 100755 (executable)
new mode 100644 (file)
index 240ab7f..d47de01
--- a/mdadm.h
+++ b/mdadm.h
@@ -383,6 +383,8 @@ enum special_options {
        ConfigFile,
        ChunkSize,
        WriteMostly,
+       FailFast,
+       NoFailFast,
        Layout,
        Auto,
        Force,
@@ -516,6 +518,7 @@ struct mddev_dev {
                                 * Not set for names read from .config
                                 */
        char writemostly;       /* 1 for 'set writemostly', 2 for 'clear writemostly' */
+       char failfast;          /* Ditto but for 'failfast' flag */
        int used;               /* set when used */
        long long data_offset;
        struct mddev_dev *next;
@@ -821,6 +824,8 @@ extern struct superswitch {
         *   linear-grow-update - now change the size of the array.
         *   writemostly - set the WriteMostly1 bit in the superblock devflags
         *   readwrite - clear the WriteMostly1 bit in the superblock devflags
+        *   failfast - set the FailFast1 bit in the superblock
+        *   nofailfast - clear the FailFast1 bit
         *   no-bitmap - clear any record that a bitmap is present.
         *   bbl       - add a bad-block-log if possible
         *   no-bbl    - remove any bad-block-log is it is empty.

diff --git a/super0.c b/super0.c
index 55ebd8bc78778457ee23354dc05fca56dd781a73..938cfd95fa25ed2fb76f723bd1b18251df95b110 100644 (file)
--- a/super0.c
+++ b/super0.c
@@ -232,14 +232,15 @@ static void examine_super0(struct supertype *st, char *homehost)
                mdp_disk_t *dp;
                char *dv;
                char nb[5];
-               int wonly;
+               int wonly, failfast;
                if (d>=0) dp = &sb->disks[d];
                else dp = &sb->this_disk;
                snprintf(nb, sizeof(nb), "%4d", d);
                printf("%4s %5d   %5d    %5d    %5d     ", d < 0 ? "this" : nb,
                       dp->number, dp->major, dp->minor, dp->raid_disk);
                wonly = dp->state & (1 << MD_DISK_WRITEMOSTLY);
-               dp->state &= ~(1 << MD_DISK_WRITEMOSTLY);
+               failfast = dp->state & (1<<MD_DISK_FAILFAST);
+               dp->state &= ~(wonly | failfast);
                if (dp->state & (1 << MD_DISK_FAULTY))
                        printf(" faulty");
                if (dp->state & (1 << MD_DISK_ACTIVE))
@@ -250,6 +251,8 @@ static void examine_super0(struct supertype *st, char *homehost)
                        printf(" removed");
                if (wonly)
                        printf(" write-mostly");
+               if (failfast)
+                       printf(" failfast");
                if (dp->state == 0)
                        printf(" spare");
                if ((dv = map_dev(dp->major, dp->minor, 0)))
@@ -581,7 +584,8 @@ static int update_super0(struct supertype *st, struct mdinfo *info,
        } else if (strcmp(update, "assemble")==0) {
                int d = info->disk.number;
                int wonly = sb->disks[d].state & (1<<MD_DISK_WRITEMOSTLY);
-               int mask = (1<<MD_DISK_WRITEMOSTLY);
+               int failfast = sb->disks[d].state & (1<<MD_DISK_FAILFAST);
+               int mask = (1<<MD_DISK_WRITEMOSTLY)|(1<<MD_DISK_FAILFAST);
                int add = 0;
                if (sb->minor_version >= 91)
                        /* During reshape we don't insist on everything
@@ -590,7 +594,7 @@ static int update_super0(struct supertype *st, struct mdinfo *info,
                        add = (1<<MD_DISK_SYNC);
                if (((sb->disks[d].state & ~mask) | add)
                    != (unsigned)info->disk.state) {
-                       sb->disks[d].state = info->disk.state | wonly;
+                       sb->disks[d].state = info->disk.state | wonly |failfast;
                        rv = 1;
                }
                if (info->reshape_active &&

diff --git a/super1.c b/super1.c
index d3234392d453234b18ecbcb4d92980bb0a758f08..87a74cb945083b7ca82e5d24293015267ac95de4 100644 (file)
--- a/super1.c
+++ b/super1.c
@@ -77,6 +77,7 @@ struct mdp_superblock_1 {
        __u8    device_uuid[16]; /* user-space setable, ignored by kernel */
        __u8    devflags;        /* per-device flags.  Only one defined...*/
 #define WriteMostly1    1        /* mask for writemostly flag in above */
+#define FailFast1      2        /* Device should get FailFast requests */
        /* bad block log.  If there are any bad blocks the feature flag is set.
         * if offset and size are non-zero, that space is reserved and available.
         */
@@ -430,6 +431,8 @@ static void examine_super1(struct supertype *st, char *homehost)
                printf("          Flags :");
                if (sb->devflags & WriteMostly1)
                        printf(" write-mostly");
+               if (sb->devflags & FailFast1)
+                       printf(" failfast");
                printf("\n");
        }
 
@@ -1020,6 +1023,8 @@ static void getinfo_super1(struct supertype *st, struct mdinfo *info, char *map)
        }
        if (sb->devflags & WriteMostly1)
                info->disk.state |= (1 << MD_DISK_WRITEMOSTLY);
+       if (sb->devflags & FailFast1)
+               info->disk.state |= (1 << MD_DISK_FAILFAST);
        info->events = __le64_to_cpu(sb->events);
        sprintf(info->text_version, "1.%d", st->minor_version);
        info->safe_mode_delay = 200;
@@ -1377,6 +1382,10 @@ static int update_super1(struct supertype *st, struct mdinfo *info,
                sb->devflags |= WriteMostly1;
        else if (strcmp(update, "readwrite")==0)
                sb->devflags &= ~WriteMostly1;
+       else if (strcmp(update, "failfast") == 0)
+               sb->devflags |= FailFast1;
+       else if (strcmp(update, "nofailfast") == 0)
+               sb->devflags &= ~FailFast1;
        else
                rv = -1;
 
@@ -1713,6 +1722,10 @@ static int write_init_super1(struct supertype *st)
                        sb->devflags |= WriteMostly1;
                else
                        sb->devflags &= ~WriteMostly1;
+               if (di->disk.state & (1<<MD_DISK_FAILFAST))
+                       sb->devflags |= FailFast1;
+               else
+                       sb->devflags &= ~FailFast1;
 
                random_uuid(sb->device_uuid);