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Message-ID: <202012011138.5766F520D9@keescook>
Date: Tue, 1 Dec 2020 11:40:28 -0800
From: Kees Cook <keescook@...omium.org>
To: Christoph Hellwig <hch@....de>
Cc: Anton Vorontsov <anton@...msg.org>,
Colin Cross <ccross@...roid.com>,
Tony Luck <tony.luck@...el.com>,
WeiXiong Liao <liaoweixiong@...winnertech.com>,
linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/9] pstore/blk: simplify the block device open / close
path
On Fri, Oct 16, 2020 at 03:20:43PM +0200, Christoph Hellwig wrote:
> Remove the pointless psblk_get_bdev and psblk_put_bdev helper,
> and don't bother holding pstore_blk_lock over the block device
> open / close interactions given that they only happen first thing
> during module init and last thing during module exit. Also don't
> bother with unregistering a zone info that did not come from the
> actually block backed code, as users like mtd have to unregister
> it themselves already.
I don't like this because it's changing too many things at once. Of the
stuff I don't want is:
- removal of checking for already-active zoneinfo (there can be only one)
- collapsing register_blk into _init (it seems clearer to me to keep
them separate)
-Kees
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
> fs/pstore/blk.c | 156 ++++++++++++------------------------------------
> 1 file changed, 38 insertions(+), 118 deletions(-)
>
> diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
> index 3a2214ecf942ae..a8aa56cba96d59 100644
> --- a/fs/pstore/blk.c
> +++ b/fs/pstore/blk.c
> @@ -91,12 +91,6 @@ static DEFINE_MUTEX(pstore_blk_lock);
> static struct block_device *psblk_bdev;
> static struct pstore_zone_info *pstore_zone_info;
>
> -struct bdev_info {
> - dev_t devt;
> - sector_t nr_sects;
> - sector_t start_sect;
> -};
> -
> #define check_size(name, alignsize) ({ \
> long _##name_ = (name); \
> _##name_ = _##name_ <= 0 ? 0 : (_##name_ * 1024); \
> @@ -205,75 +199,6 @@ void unregister_pstore_device(struct pstore_device_info *dev)
> }
> EXPORT_SYMBOL_GPL(unregister_pstore_device);
>
> -/**
> - * psblk_get_bdev() - open block device
> - *
> - * @holder: Exclusive holder identifier
> - * @info: Information about bdev to fill in
> - *
> - * Return: pointer to block device on success and others on error.
> - *
> - * On success, the returned block_device has reference count of one.
> - */
> -static struct block_device *psblk_get_bdev(void *holder,
> - struct bdev_info *info)
> -{
> - struct block_device *bdev = ERR_PTR(-ENODEV);
> - fmode_t mode = FMODE_READ | FMODE_WRITE;
> - sector_t nr_sects;
> -
> - lockdep_assert_held(&pstore_blk_lock);
> -
> - if (pstore_zone_info)
> - return ERR_PTR(-EBUSY);
> -
> - if (!blkdev[0])
> - return ERR_PTR(-ENODEV);
> -
> - if (holder)
> - mode |= FMODE_EXCL;
> - bdev = blkdev_get_by_path(blkdev, mode, holder);
> - if (IS_ERR(bdev)) {
> - dev_t devt;
> -
> - devt = name_to_dev_t(blkdev);
> - if (devt == 0)
> - return ERR_PTR(-ENODEV);
> - bdev = blkdev_get_by_dev(devt, mode, holder);
> - if (IS_ERR(bdev))
> - return bdev;
> - }
> -
> - nr_sects = part_nr_sects_read(bdev->bd_part);
> - if (!nr_sects) {
> - pr_err("not enough space for '%s'\n", blkdev);
> - blkdev_put(bdev, mode);
> - return ERR_PTR(-ENOSPC);
> - }
> -
> - if (info) {
> - info->devt = bdev->bd_dev;
> - info->nr_sects = nr_sects;
> - info->start_sect = get_start_sect(bdev);
> - }
> -
> - return bdev;
> -}
> -
> -static void psblk_put_bdev(struct block_device *bdev, void *holder)
> -{
> - fmode_t mode = FMODE_READ | FMODE_WRITE;
> -
> - lockdep_assert_held(&pstore_blk_lock);
> -
> - if (!bdev)
> - return;
> -
> - if (holder)
> - mode |= FMODE_EXCL;
> - blkdev_put(bdev, mode);
> -}
> -
> static ssize_t psblk_generic_blk_read(char *buf, size_t bytes, loff_t pos)
> {
> struct block_device *bdev = psblk_bdev;
> @@ -340,29 +265,39 @@ static ssize_t psblk_generic_blk_write(const char *buf, size_t bytes,
> return ret;
> }
>
> -static int __register_pstore_blk(void)
> +static int __init pstore_blk_init(void)
> {
> char bdev_name[BDEVNAME_SIZE];
> struct block_device *bdev;
> struct pstore_device_info dev;
> - struct bdev_info binfo;
> - void *holder = blkdev;
> int ret = -ENODEV;
> -
> - lockdep_assert_held(&pstore_blk_lock);
> + fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
> + sector_t nr_sects;
> +
> + if (!best_effort || !blkdev[0])
> + return 0;
>
> /* hold bdev exclusively */
> - memset(&binfo, 0, sizeof(binfo));
> - bdev = psblk_get_bdev(holder, &binfo);
> + bdev = blkdev_get_by_path(blkdev, mode, blkdev);
> if (IS_ERR(bdev)) {
> - pr_err("failed to open '%s'!\n", blkdev);
> - return PTR_ERR(bdev);
> + dev_t devt;
> +
> + devt = name_to_dev_t(blkdev);
> + if (devt == 0) {
> + pr_err("failed to open '%s'!\n", blkdev);
> + return -ENODEV;
> + }
> + bdev = blkdev_get_by_dev(devt, mode, blkdev);
> + if (IS_ERR(bdev)) {
> + pr_err("failed to open '%s'!\n", blkdev);
> + return PTR_ERR(bdev);
> + }
> }
>
> - /* only allow driver matching the @blkdev */
> - if (!binfo.devt) {
> - pr_debug("no major\n");
> - ret = -ENODEV;
> + nr_sects = part_nr_sects_read(bdev->bd_part);
> + if (!nr_sects) {
> + pr_err("not enough space for '%s'\n", blkdev);
> + ret = -ENOSPC;
> goto err_put_bdev;
> }
>
> @@ -370,11 +305,11 @@ static int __register_pstore_blk(void)
> psblk_bdev = bdev;
>
> memset(&dev, 0, sizeof(dev));
> - dev.total_size = binfo.nr_sects << SECTOR_SHIFT;
> + dev.total_size = nr_sects << SECTOR_SHIFT;
> dev.read = psblk_generic_blk_read;
> dev.write = psblk_generic_blk_write;
>
> - ret = __register_pstore_device(&dev);
> + ret = register_pstore_device(&dev);
> if (ret)
> goto err_put_bdev;
>
> @@ -383,10 +318,22 @@ static int __register_pstore_blk(void)
> return 0;
>
> err_put_bdev:
> + blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
> psblk_bdev = NULL;
> - psblk_put_bdev(bdev, holder);
> return ret;
> }
> +late_initcall(pstore_blk_init);
> +
> +static void __exit pstore_blk_exit(void)
> +{
> + struct pstore_device_info dev = { .read = psblk_generic_blk_read };
> +
> + if (!psblk_bdev)
> + return;
> + unregister_pstore_device(&dev);
> + blkdev_put(psblk_bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
> +}
> +module_exit(pstore_blk_exit);
>
> /* get information of pstore/blk */
> int pstore_blk_get_config(struct pstore_blk_config *info)
> @@ -402,33 +349,6 @@ int pstore_blk_get_config(struct pstore_blk_config *info)
> }
> EXPORT_SYMBOL_GPL(pstore_blk_get_config);
>
> -static int __init pstore_blk_init(void)
> -{
> - int ret = 0;
> -
> - mutex_lock(&pstore_blk_lock);
> - if (!pstore_zone_info && best_effort && blkdev[0])
> - ret = __register_pstore_blk();
> - mutex_unlock(&pstore_blk_lock);
> -
> - return ret;
> -}
> -late_initcall(pstore_blk_init);
> -
> -static void __exit pstore_blk_exit(void)
> -{
> - struct pstore_device_info dev = { };
> -
> - mutex_lock(&pstore_blk_lock);
> - if (pstore_zone_info)
> - dev.read = pstore_zone_info->read;
> - __unregister_pstore_device(&dev);
> - if (psblk_bdev)
> - psblk_put_bdev(psblk_bdev, blkdev);
> - mutex_unlock(&pstore_blk_lock);
> -}
> -module_exit(pstore_blk_exit);
> -
> MODULE_LICENSE("GPL");
> MODULE_AUTHOR("WeiXiong Liao <liaoweixiong@...winnertech.com>");
> MODULE_AUTHOR("Kees Cook <keescook@...omium.org>");
> --
> 2.28.0
>
--
Kees Cook
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