| Message ID | 1347211634-11509-7-git-send-email-dmonakhov@openvz.org |
|---|---|
| State | Superseded, archived |
| Headers | show |
Hi Dmitry, Could you please provide more detailed workload to convince me? I am thinking about whether we really need to disable dioread_nolock feature in here. In our benchmarks, we don't see this problem. Regards, Zheng On Sun, Sep 09, 2012 at 09:27:13PM +0400, Dmitry Monakhov wrote: > If we have enough aggressive DIO readers, truncate and other dio > waiters will wait forever inside inode_dio_wait(). It is reasonable > to disable nonlock DIO read optimization during truncate. > > Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org> > --- > fs/ext4/extents.c | 2 +- > fs/ext4/fsync.c | 2 +- > fs/ext4/inode.c | 2 +- > 3 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index 8252651..b5b801f 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -4853,7 +4853,7 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > } > > /* finish any pending end_io work */ > - inode_dio_wait(inode); > + ext4_inode_dio_wait(inode, 1); > ext4_flush_completed_IO(inode); > > credits = ext4_writepage_trans_blocks(inode); > diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c > index 290c5cf..bdf6bfd 100644 > --- a/fs/ext4/fsync.c > +++ b/fs/ext4/fsync.c > @@ -204,7 +204,7 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync) > if (inode->i_sb->s_flags & MS_RDONLY) > goto out; > > - inode_dio_wait(inode); > + ext4_inode_dio_wait(inode, 1); > ret = ext4_flush_completed_IO(inode); > if (ret < 0) > goto out; > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 93e6b09..a850026 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -4335,7 +4335,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) > truncate_setsize(inode, attr->ia_size); > /* Inode size will be reduced, wait for dio in flight */ > if (orphan) > - inode_dio_wait(inode); > + ext4_inode_dio_wait(inode, 1); > } > ext4_truncate(inode); > } > -- > 1.7.7.6 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello, On Thu 13-09-12 18:41:36, Zheng Liu wrote: > Could you please provide more detailed workload to convince me? I > am thinking about whether we really need to disable dioread_nolock > feature in here. In our benchmarks, we don't see this problem. I just did: # Create file dd if=/dev/zero of=/mnt/file bs=1M count=30 sync # Start 10 DIO dio readers in parallel reading the file in a loop for (( i = 0; i < 10; i++ )); do while true; do dd if=/mnt/file bs=4k iflag=direct of=/dev/null done & done sleep 1 # Try to truncate the file - never finishes. truncate -s 16 /mnt/file It is pretty easy to hit this. Besides being a DOS attack vector (but I won't be too concerned about this - there are plenty of ways how local process can screw you) I can easily imagine some application to get bitten by this. Honza > > Regards, > Zheng > > On Sun, Sep 09, 2012 at 09:27:13PM +0400, Dmitry Monakhov wrote: > > If we have enough aggressive DIO readers, truncate and other dio > > waiters will wait forever inside inode_dio_wait(). It is reasonable > > to disable nonlock DIO read optimization during truncate. > > > > Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org> > > --- > > fs/ext4/extents.c | 2 +- > > fs/ext4/fsync.c | 2 +- > > fs/ext4/inode.c | 2 +- > > 3 files changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > > index 8252651..b5b801f 100644 > > --- a/fs/ext4/extents.c > > +++ b/fs/ext4/extents.c > > @@ -4853,7 +4853,7 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > > } > > > > /* finish any pending end_io work */ > > - inode_dio_wait(inode); > > + ext4_inode_dio_wait(inode, 1); > > ext4_flush_completed_IO(inode); > > > > credits = ext4_writepage_trans_blocks(inode); > > diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c > > index 290c5cf..bdf6bfd 100644 > > --- a/fs/ext4/fsync.c > > +++ b/fs/ext4/fsync.c > > @@ -204,7 +204,7 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync) > > if (inode->i_sb->s_flags & MS_RDONLY) > > goto out; > > > > - inode_dio_wait(inode); > > + ext4_inode_dio_wait(inode, 1); > > ret = ext4_flush_completed_IO(inode); > > if (ret < 0) > > goto out; > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > > index 93e6b09..a850026 100644 > > --- a/fs/ext4/inode.c > > +++ b/fs/ext4/inode.c > > @@ -4335,7 +4335,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) > > truncate_setsize(inode, attr->ia_size); > > /* Inode size will be reduced, wait for dio in flight */ > > if (orphan) > > - inode_dio_wait(inode); > > + ext4_inode_dio_wait(inode, 1); > > } > > ext4_truncate(inode); > > } > > -- > > 1.7.7.6 > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Sep 13, 2012 at 02:07:36PM +0200, Jan Kara wrote: > Hello, > > On Thu 13-09-12 18:41:36, Zheng Liu wrote: > > Could you please provide more detailed workload to convince me? I > > am thinking about whether we really need to disable dioread_nolock > > feature in here. In our benchmarks, we don't see this problem. > I just did: > > # Create file > dd if=/dev/zero of=/mnt/file bs=1M count=30 > sync > # Start 10 DIO dio readers in parallel reading the file in a loop > for (( i = 0; i < 10; i++ )); do > while true; do > dd if=/mnt/file bs=4k iflag=direct of=/dev/null > done & > done > sleep 1 > > # Try to truncate the file - never finishes. > truncate -s 16 /mnt/file > > It is pretty easy to hit this. Besides being a DOS attack vector (but I > won't be too concerned about this - there are plenty of ways how local > process can screw you) I can easily imagine some application to get bitten > by this. Hi Jan, Thanks for your explanation, but in my desktop I cannot reproduce this problem. The size of `file' is 16. Am I missing something? Regards, Zheng -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu 13-09-12 20:57:26, Zheng Liu wrote: > On Thu, Sep 13, 2012 at 02:07:36PM +0200, Jan Kara wrote: > > Hello, > > > > On Thu 13-09-12 18:41:36, Zheng Liu wrote: > > > Could you please provide more detailed workload to convince me? I > > > am thinking about whether we really need to disable dioread_nolock > > > feature in here. In our benchmarks, we don't see this problem. > > I just did: > > > > # Create file > > dd if=/dev/zero of=/mnt/file bs=1M count=30 > > sync > > # Start 10 DIO dio readers in parallel reading the file in a loop > > for (( i = 0; i < 10; i++ )); do > > while true; do > > dd if=/mnt/file bs=4k iflag=direct of=/dev/null > > done & > > done > > sleep 1 > > > > # Try to truncate the file - never finishes. > > truncate -s 16 /mnt/file > > > > It is pretty easy to hit this. Besides being a DOS attack vector (but I > > won't be too concerned about this - there are plenty of ways how local > > process can screw you) I can easily imagine some application to get bitten > > by this. > > Hi Jan, > > Thanks for your explanation, but in my desktop I cannot reproduce this > problem. The size of `file' is 16. Am I missing something? Hum, on my test machine with 3.6-rc1 it does not... Maybe for your desktop you need a larger sleep before running truncate so that readers have time to start up? Also I suppose you have ext4 mounted with dioread_nolock mount option? Honza
On Thu, Sep 13, 2012 at 04:34:55PM +0200, Jan Kara wrote: > On Thu 13-09-12 20:57:26, Zheng Liu wrote: > > On Thu, Sep 13, 2012 at 02:07:36PM +0200, Jan Kara wrote: > > > Hello, > > > > > > On Thu 13-09-12 18:41:36, Zheng Liu wrote: > > > > Could you please provide more detailed workload to convince me? I > > > > am thinking about whether we really need to disable dioread_nolock > > > > feature in here. In our benchmarks, we don't see this problem. > > > I just did: > > > > > > # Create file > > > dd if=/dev/zero of=/mnt/file bs=1M count=30 > > > sync > > > # Start 10 DIO dio readers in parallel reading the file in a loop > > > for (( i = 0; i < 10; i++ )); do > > > while true; do > > > dd if=/mnt/file bs=4k iflag=direct of=/dev/null > > > done & > > > done > > > sleep 1 > > > > > > # Try to truncate the file - never finishes. > > > truncate -s 16 /mnt/file > > > > > > It is pretty easy to hit this. Besides being a DOS attack vector (but I > > > won't be too concerned about this - there are plenty of ways how local > > > process can screw you) I can easily imagine some application to get bitten > > > by this. > > > > Hi Jan, > > > > Thanks for your explanation, but in my desktop I cannot reproduce this > > problem. The size of `file' is 16. Am I missing something? > Hum, on my test machine with 3.6-rc1 it does not... Maybe for your > desktop you need a larger sleep before running truncate so that readers > have time to start up? Also I suppose you have ext4 mounted with > dioread_nolock mount option? Yes, it can be reproduced after increasing sleep time. Thanks. Regards, Zheng -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 8252651..b5b801f 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4853,7 +4853,7 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) } /* finish any pending end_io work */ - inode_dio_wait(inode); + ext4_inode_dio_wait(inode, 1); ext4_flush_completed_IO(inode); credits = ext4_writepage_trans_blocks(inode); diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c index 290c5cf..bdf6bfd 100644 --- a/fs/ext4/fsync.c +++ b/fs/ext4/fsync.c @@ -204,7 +204,7 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync) if (inode->i_sb->s_flags & MS_RDONLY) goto out; - inode_dio_wait(inode); + ext4_inode_dio_wait(inode, 1); ret = ext4_flush_completed_IO(inode); if (ret < 0) goto out; diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 93e6b09..a850026 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4335,7 +4335,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) truncate_setsize(inode, attr->ia_size); /* Inode size will be reduced, wait for dio in flight */ if (orphan) - inode_dio_wait(inode); + ext4_inode_dio_wait(inode, 1); } ext4_truncate(inode); }
If we have enough aggressive DIO readers, truncate and other dio waiters will wait forever inside inode_dio_wait(). It is reasonable to disable nonlock DIO read optimization during truncate. Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org> --- fs/ext4/extents.c | 2 +- fs/ext4/fsync.c | 2 +- fs/ext4/inode.c | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-)