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    SubjectRe: per BDI dirty limit (was Re: -mm merge plans for 2.6.24)
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    Date
    Hi,

    Thanks for the help so far, however we're still not quite there.

    The below patch still has the funny 20 character name limit. Is there a
    good reason its a char array like this, and not just a char * to a kstr?
    The code does kstrdup all over the place, I can't imagine why suddenly
    limiting it to 20 chars seems like a good idea.


    Mounting NFS filesystems: mount: 192.168.0.1:/mnt/ying failed, reason given by server: Permission denied
    mount: 192.168.0.1:/mnt/yang failed, reason given by server: Permission denied
    [ 52.705052] sysfs: duplicate filename 'bdi-nfs-192.168.0.1' can not be created
    [ 52.712517] WARNING: at /mnt/md0/src/linux-2.6-2/fs/sysfs/dir.c:424 sysfs_add_one()
    [ 52.720243]
    [ 52.720244] Call Trace:
    [ 52.724311] [<ffffffff80304f7c>] sysfs_add_one+0xac/0xe0
    [ 52.729708] [<ffffffff80305613>] create_dir+0x63/0xc0
    [ 52.734832] [<ffffffff803056a4>] sysfs_create_dir+0x34/0x50
    [ 52.740489] [<ffffffff804d5710>] _spin_unlock+0x30/0x60
    [ 52.745792] [<ffffffff8036958e>] kobject_add+0xbe/0x200
    [ 52.751094] [<ffffffff803dfc40>] device_add+0xc0/0x680
    [ 52.756305] [<ffffffff803e0219>] device_register+0x19/0x20
    [ 52.761877] [<ffffffff803e0697>] device_create+0xe7/0x120
    [ 52.767360] [<ffffffff8036e0bc>] vsnprintf+0x2bc/0x690
    [ 52.772585] [<ffffffff80370380>] kvasprintf+0x70/0x90
    [ 52.777724] [<ffffffff80295bbb>] bdi_register+0x9b/0xe0
    [ 52.783037] [<ffffffff8037e039>] percpu_counter_init_irq+0x39/0x50
    [ 52.789299] [<ffffffff8036abcc>] prop_local_init_percpu+0x3c/0x50
    [ 52.795462] [<ffffffff80295a41>] bdi_init+0x61/0xb0
    [ 52.800411] [<ffffffff80308069>] nfs_probe_fsinfo+0x4d9/0x640
    [ 52.806226] [<ffffffff80308f9a>] nfs_create_server+0x1ea/0x560
    [ 52.812123] [<ffffffff80263526>] lock_release_holdtime+0x66/0x80
    [ 52.818217] [<ffffffff802ca936>] __d_lookup+0x106/0x1d0
    [ 52.823529] [<ffffffff802b0fd5>] __kmalloc_track_caller+0xa5/0x100
    [ 52.829789] [<ffffffff80266185>] trace_hardirqs_on+0xd5/0x170
    [ 52.835618] [<ffffffff80312412>] nfs_get_sb+0x2b2/0x740
    [ 52.840931] [<ffffffff80312459>] nfs_get_sb+0x2f9/0x740
    [ 52.846245] [<ffffffff802d0000>] __put_mnt_ns+0x90/0xa0
    [ 52.851556] [<ffffffff802b89db>] vfs_kern_mount+0xbb/0x150
    [ 52.857127] [<ffffffff802b8ade>] do_kern_mount+0x4e/0x100
    [ 52.862614] [<ffffffff802d122c>] do_mount+0x4dc/0x7a0
    [ 52.867751] [<ffffffff80266185>] trace_hardirqs_on+0xd5/0x170
    [ 52.873580] [<ffffffff804d5842>] _spin_unlock_irqrestore+0x42/0x80
    [ 52.879841] [<ffffffff8036c505>] __up_read+0x45/0xb0
    [ 52.884894] [<ffffffff80255aa5>] search_exception_tables+0x25/0x40
    [ 52.891155] [<ffffffff8028d1d5>] get_page_from_freelist+0x4a5/0x760
    [ 52.897487] [<ffffffff8028a58f>] bad_range+0x1f/0x80
    [ 52.902540] [<ffffffff8028d0b7>] get_page_from_freelist+0x387/0x760
    [ 52.908888] [<ffffffff8028d54e>] __alloc_pages+0x6e/0x3b0
    [ 52.914374] [<ffffffff802a80ea>] alloc_pages_current+0x5a/0x90
    [ 52.920290] [<ffffffff8028c97b>] __get_free_pages+0x1b/0x40
    [ 52.925929] [<ffffffff802cf892>] copy_mount_options+0x52/0x170
    [ 52.931827] [<ffffffff802d1584>] sys_mount+0x94/0xe0
    [ 52.936881] [<ffffffff804d49cd>] trace_hardirqs_on_thunk+0x35/0x3a
    [ 52.943141] [<ffffffff8020c43e>] system_call+0x7e/0x83
    [ 52.948357]
    [ 52.949850] kobject_add failed for bdi-nfs-192.168.0.1 with -EEXIST, don't try to register things with the same name in the same directory.
    [ 52.962332]

    (just in case it wasn't obvious, the -%p part that was supposed to make
    it unique got truncated)

    ---
    block/genhd.c | 3 +
    fs/fuse/inode.c | 3 -
    fs/nfs/client.c | 3 -
    include/linux/backing-dev.h | 19 +++++++
    include/linux/writeback.h | 3 +
    lib/percpu_counter.c | 1
    mm/backing-dev.c | 107 ++++++++++++++++++++++++++++++++++++++++++++
    mm/page-writeback.c | 2
    8 files changed, 138 insertions(+), 3 deletions(-)

    Index: linux-2.6-2/block/genhd.c
    ===================================================================
    --- linux-2.6-2.orig/block/genhd.c
    +++ linux-2.6-2/block/genhd.c
    @@ -182,6 +182,8 @@ void add_disk(struct gendisk *disk)
    disk->minors, NULL, exact_match, exact_lock, disk);
    register_disk(disk);
    blk_register_queue(disk);
    + bdi_register(&disk->queue->backing_dev_info, NULL,
    + "bdi-%s", disk->disk_name);
    }

    EXPORT_SYMBOL(add_disk);
    @@ -190,6 +192,7 @@ EXPORT_SYMBOL(del_gendisk); /* in partit
    void unlink_gendisk(struct gendisk *disk)
    {
    blk_unregister_queue(disk);
    + bdi_unregister(&disk->queue->backing_dev_info);
    blk_unregister_region(MKDEV(disk->major, disk->first_minor),
    disk->minors);
    }
    Index: linux-2.6-2/fs/fuse/inode.c
    ===================================================================
    --- linux-2.6-2.orig/fs/fuse/inode.c
    +++ linux-2.6-2/fs/fuse/inode.c
    @@ -467,7 +467,8 @@ static struct fuse_conn *new_conn(void)
    atomic_set(&fc->num_waiting, 0);
    fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
    fc->bdi.unplug_io_fn = default_unplug_io_fn;
    - err = bdi_init(&fc->bdi);
    + err = bdi_init_fmt(&fc->bdi, NULL,
    + "bdi-fuse-%llu", (unsigned long long)fc->id);
    if (err) {
    kfree(fc);
    fc = NULL;
    Index: linux-2.6-2/fs/nfs/client.c
    ===================================================================
    --- linux-2.6-2.orig/fs/nfs/client.c
    +++ linux-2.6-2/fs/nfs/client.c
    @@ -678,7 +678,8 @@ static int nfs_probe_fsinfo(struct nfs_s
    goto out_error;

    nfs_server_set_fsinfo(server, &fsinfo);
    - error = bdi_init(&server->backing_dev_info);
    + error = bdi_init_fmt(&server->backing_dev_info, NULL,
    + "bdi-nfs-%s-%p", clp->cl_hostname, server);
    if (error)
    goto out_error;

    Index: linux-2.6-2/include/linux/backing-dev.h
    ===================================================================
    --- linux-2.6-2.orig/include/linux/backing-dev.h
    +++ linux-2.6-2/include/linux/backing-dev.h
    @@ -11,6 +11,8 @@
    #include <linux/percpu_counter.h>
    #include <linux/log2.h>
    #include <linux/proportions.h>
    +#include <linux/kernel.h>
    +#include <linux/device.h>
    #include <asm/atomic.h>

    struct page;
    @@ -48,11 +50,28 @@ struct backing_dev_info {

    struct prop_local_percpu completions;
    int dirty_exceeded;
    +
    + struct device *dev;
    };

    int bdi_init(struct backing_dev_info *bdi);
    void bdi_destroy(struct backing_dev_info *bdi);

    +int bdi_register(struct backing_dev_info *bdi, struct device *parent,
    + const char *fmt, ...);
    +void bdi_unregister(struct backing_dev_info *bdi);
    +
    +#define bdi_init_fmt(bdi, parent, fmt...) \
    + ({ \
    + int ret = bdi_init(bdi); \
    + if (!ret) { \
    + ret = bdi_register(bdi, parent, ##fmt); \
    + if (ret) \
    + bdi_destroy(bdi); \
    + } \
    + ret; \
    + })
    +
    static inline void __add_bdi_stat(struct backing_dev_info *bdi,
    enum bdi_stat_item item, s64 amount)
    {
    Index: linux-2.6-2/include/linux/writeback.h
    ===================================================================
    --- linux-2.6-2.orig/include/linux/writeback.h
    +++ linux-2.6-2/include/linux/writeback.h
    @@ -113,6 +113,9 @@ struct file;
    int dirty_writeback_centisecs_handler(struct ctl_table *, int, struct file *,
    void __user *, size_t *, loff_t *);

    +void get_dirty_limits(long *pbackground, long *pdirty, long *pbdi_dirty,
    + struct backing_dev_info *bdi);
    +
    void page_writeback_init(void);
    void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
    unsigned long nr_pages_dirtied);
    Index: linux-2.6-2/mm/backing-dev.c
    ===================================================================
    --- linux-2.6-2.orig/mm/backing-dev.c
    +++ linux-2.6-2/mm/backing-dev.c
    @@ -4,12 +4,115 @@
    #include <linux/fs.h>
    #include <linux/sched.h>
    #include <linux/module.h>
    +#include <linux/writeback.h>
    +#include <linux/device.h>
    +
    +
    +static struct class *bdi_class;
    +
    +static ssize_t readahead_store(struct device *dev,
    + struct device_attribute *attr,
    + const char *buf, size_t count)
    +{
    + struct backing_dev_info *bdi = dev_get_drvdata(dev);
    + char *end;
    +
    + bdi->ra_pages = simple_strtoul(buf, &end, 10);
    +
    + return end - buf;
    +}
    +
    +#define BDI_SHOW(name, expr) \
    +static ssize_t name##_show(struct device *dev, \
    + struct device_attribute *attr, char *page) \
    +{ \
    + struct backing_dev_info *bdi = dev_get_drvdata(dev); \
    + \
    + return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
    +}
    +
    +BDI_SHOW(readahead, bdi->ra_pages)
    +
    +BDI_SHOW(reclaimable, bdi_stat(bdi, BDI_RECLAIMABLE))
    +BDI_SHOW(writeback, bdi_stat(bdi, BDI_WRITEBACK))
    +
    +static inline unsigned long get_dirty(struct backing_dev_info *bdi, int i)
    +{
    + unsigned long thresh[3];
    +
    + get_dirty_limits(&thresh[0], &thresh[1], &thresh[2], bdi);
    +
    + return thresh[i];
    +}
    +
    +BDI_SHOW(dirty, get_dirty(bdi, 1))
    +BDI_SHOW(bdi_dirty, get_dirty(bdi, 2))
    +
    +static struct device_attribute bdi_dev_attrs[] = {
    + __ATTR(readahead, 0644, readahead_show, readahead_store),
    + __ATTR_RO(reclaimable),
    + __ATTR_RO(writeback),
    + __ATTR_RO(dirty),
    + __ATTR_RO(bdi_dirty),
    + __ATTR_NULL,
    +};
    +
    +static __init int bdi_class_init(void)
    +{
    + bdi_class = class_create(THIS_MODULE, "bdi");
    + bdi_class->dev_attrs = bdi_dev_attrs;
    + return 0;
    +}
    +
    +__initcall(bdi_class_init);
    +
    +int bdi_register(struct backing_dev_info *bdi, struct device *parent,
    + const char *fmt, ...)
    +{
    + char *name;
    + va_list args;
    + int ret = 0;
    + struct device *dev;
    +
    + va_start(args, fmt);
    + name = kvasprintf(GFP_KERNEL, fmt, args);
    + va_end(args);
    +
    + if (!name)
    + return -ENOMEM;
    +
    + dev = device_create(bdi_class, parent, MKDEV(0,0), name);
    + if (IS_ERR(dev)) {
    + ret = PTR_ERR(dev);
    + goto exit;
    + }
    +
    + bdi->dev = dev;
    + dev_set_drvdata(bdi->dev, bdi);
    +
    +exit:
    + kfree(name);
    + return ret;
    +}
    +
    +void bdi_unregister(struct backing_dev_info *bdi)
    +{
    + if (bdi->dev) {
    + device_unregister(bdi->dev);
    + bdi->dev = NULL;
    + }
    +}
    +
    +EXPORT_SYMBOL(bdi_register);
    +EXPORT_SYMBOL(bdi_unregister);

    int bdi_init(struct backing_dev_info *bdi)
    {
    int i, j;
    int err;

    + bdi->dev = NULL;
    +
    for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
    err = percpu_counter_init_irq(&bdi->bdi_stat[i], 0);
    if (err)
    @@ -33,6 +136,8 @@ void bdi_destroy(struct backing_dev_info
    {
    int i;

    + bdi_unregister(bdi);
    +
    for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
    percpu_counter_destroy(&bdi->bdi_stat[i]);

    Index: linux-2.6-2/mm/page-writeback.c
    ===================================================================
    --- linux-2.6-2.orig/mm/page-writeback.c
    +++ linux-2.6-2/mm/page-writeback.c
    @@ -291,7 +291,7 @@ static unsigned long determine_dirtyable
    return x + 1; /* Ensure that we never return 0 */
    }

    -static void
    +void
    get_dirty_limits(long *pbackground, long *pdirty, long *pbdi_dirty,
    struct backing_dev_info *bdi)
    {
    Index: linux-2.6-2/lib/percpu_counter.c
    ===================================================================
    --- linux-2.6-2.orig/lib/percpu_counter.c
    +++ linux-2.6-2/lib/percpu_counter.c
    @@ -102,6 +102,7 @@ void percpu_counter_destroy(struct percp
    return;

    free_percpu(fbc->counters);
    + fbc->counters = NULL;
    #ifdef CONFIG_HOTPLUG_CPU
    mutex_lock(&percpu_counters_lock);
    list_del(&fbc->list);

    -
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