Re: [PATCH] block: Fix S_DAX inode flag locking
From: Dan Williams <hidden>
Date: 2016-05-17 19:34:58
Also in:
linux-fsdevel
On Tue, May 17, 2016 at 11:29 AM, Jon Derrick [off-list ref] wrote:
This patch fixes S_DAX bd_inode i_flag locking to conform to suggested
A "fix" implies that its currently broken. I don't see how it is, not until we add an ioctl method or other path that also tries to update the flags outside of blkdev_get() context. So, I don't think this patch stands on its own if you were intending it to be merged separately.
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locking rules. It is presumed that S_DAX is the only valid inode flag for a block device which subscribes to direct-access, and will restore any previously set flags if direct-access initialization fails. This reverts to i_flags behavior prior to bbab37ddc20bae4709bca8745c128c4f46fe63c5 by allowing other bd_inode flags when DAX is disabled Signed-off-by: Jon Derrick <redacted> --- fs/block_dev.c | 31 ++++++++++++++++++++++++++----- 1 file changed, 26 insertions(+), 5 deletions(-)diff --git a/fs/block_dev.c b/fs/block_dev.c index 20a2c02..d41e37f 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c@@ -1159,6 +1159,20 @@ void bd_set_size(struct block_device *bdev, loff_t size) } EXPORT_SYMBOL(bd_set_size); +static void bd_add_dax(struct inode *inode) +{ + inode_lock(inode); + inode->i_flags |= S_DAX; + inode_unlock(inode); +} + +static void bd_clear_dax(struct inode *inode) +{ + inode_lock(inode); + inode->i_flags &= ~S_DAX; + inode_unlock(inode); +}
Since this is inode generic should these helpers be prefixed "i_" rather than "bd_"?
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+ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part); /*@@ -1172,6 +1186,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) { struct gendisk *disk; struct module *owner; + struct inode *inode; int ret; int partno; int perm = 0;@@ -1198,6 +1213,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) if (!disk) goto out; owner = disk->fops->owner; + inode = bdev->bd_inode; disk_block_events(disk); mutex_lock_nested(&bdev->bd_mutex, for_part);@@ -1206,9 +1222,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) bdev->bd_queue = disk->queue; bdev->bd_contains = bdev; if (IS_ENABLED(CONFIG_BLK_DEV_DAX) && disk->fops->direct_access) - bdev->bd_inode->i_flags = S_DAX; - else - bdev->bd_inode->i_flags = 0; + bd_add_dax(inode); if (!partno) { ret = -ENXIO;@@ -1228,6 +1242,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) bdev->bd_part = NULL; bdev->bd_disk = NULL; bdev->bd_queue = NULL; + bd_clear_dax(inode); mutex_unlock(&bdev->bd_mutex); disk_unblock_events(disk); put_disk(disk);@@ -1239,7 +1254,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) if (!ret) { bd_set_size(bdev,(loff_t)get_capacity(disk)<<9); if (!blkdev_dax_capable(bdev)) - bdev->bd_inode->i_flags &= ~S_DAX; + bd_clear_dax(inode); } /*@@ -1276,7 +1291,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) } bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9); if (!blkdev_dax_capable(bdev)) - bdev->bd_inode->i_flags &= ~S_DAX; + bd_clear_dax(inode); } } else { if (bdev->bd_contains == bdev) {@@ -1297,6 +1312,11 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) put_disk(disk); module_put(owner); } + inode_lock(inode); + if (inode->i_flags & S_DAX) + inode->i_flags = S_DAX; + inode_unlock(inode); +
Clear all other flags if S_DAX is set? Why?
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bdev->bd_openers++; if (for_part) bdev->bd_part_count++;@@ -1309,6 +1329,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) bdev->bd_disk = NULL; bdev->bd_part = NULL; bdev->bd_queue = NULL; + bd_clear_dax(inode);
Why?