Message ID | 1342943986-12413-10-git-send-email-wenqing.lz@taobao.com |
---|---|
State | Superseded, archived |
Headers | show |
On Sun, 22 Jul 2012, Zheng Liu wrote: > Date: Sun, 22 Jul 2012 15:59:45 +0800 > From: Zheng Liu <gnehzuil.liu@gmail.com> > To: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org > Cc: xiaoqiangnk@gmail.com, achender@linux.vnet.ibm.com, wenqing.lz@taobao.com > Subject: [RFC][PATCH 09/10 v1][RESEND] ext4: don't need to writeout all dirty > pages in punch hole > > From: Zheng Liu <wenqing.lz@taobao.com> > > Now we don't need to writeout all dirty pages when punching a hole. The i_mutex > locking is taken to avoid concurrent writes. In truncate_pagecache_range, all > pages in this hole is released, and ext4_es_remove_space is called to update > extent status tree. Hi Zheng, I am currently in the middle of reworking punch hole for ext4 so there will be some changes in this area. See the patch set http://www.spinics.net/lists/linux-ext4/msg33014.html Moreover I think that we should avoid taking i_mutex if we can and I believe that we can in this case, because we only need to prevent allocation. So I just want to let you know that this part is probably going to change anyway. Thanks! -Lukas > > Signed-off-by: Zheng Liu <wenqing.lz@taobao.com> > --- > fs/ext4/extents.c | 28 ++++++++++++---------------- > 1 files changed, 12 insertions(+), 16 deletions(-) > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index f2c5294..2a526b4 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -4529,9 +4529,11 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > loff_t first_page_offset, last_page_offset; > int credits, err = 0; > > + mutex_lock(&inode->i_mutex); > + > /* No need to punch hole beyond i_size */ > if (offset >= inode->i_size) > - return 0; > + goto error; > > /* > * If the hole extends beyond i_size, set the hole > @@ -4549,18 +4551,6 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > first_page_offset = first_page << PAGE_CACHE_SHIFT; > last_page_offset = last_page << PAGE_CACHE_SHIFT; > > - /* > - * Write out all dirty pages to avoid race conditions > - * Then release them. > - */ > - if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) { > - err = filemap_write_and_wait_range(mapping, > - offset, offset + length - 1); > - > - if (err) > - return err; > - } > - > /* Now release the pages */ > if (last_page_offset > first_page_offset) { > truncate_pagecache_range(inode, first_page_offset, > @@ -4572,12 +4562,14 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > > credits = ext4_writepage_trans_blocks(inode); > handle = ext4_journal_start(inode, credits); > - if (IS_ERR(handle)) > - return PTR_ERR(handle); > + if (IS_ERR(handle)) { > + err = PTR_ERR(handle); > + goto error; > + } > > err = ext4_orphan_add(handle, inode); > if (err) > - goto out; > + goto error; > > /* > * Now we need to zero out the non-page-aligned data in the > @@ -4652,6 +4644,8 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > ext4_ext_invalidate_cache(inode); > ext4_discard_preallocations(inode); > > + err = ext4_es_remove_space(inode, first_block, > + stop_block - first_block); > err = ext4_ext_remove_space(inode, first_block, stop_block - 1); > > ext4_ext_invalidate_cache(inode); > @@ -4667,6 +4661,8 @@ out: > inode->i_mtime = inode->i_ctime = ext4_current_time(inode); > ext4_mark_inode_dirty(handle, inode); > ext4_journal_stop(handle); > +error: > + mutex_unlock(&inode->i_mutex); > return err; > } > int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, > -- 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
Hi Lukas, On Mon, Jul 23, 2012 at 01:01:53PM +0200, Lukáš Czerner wrote: > On Sun, 22 Jul 2012, Zheng Liu wrote: > > > Date: Sun, 22 Jul 2012 15:59:45 +0800 > > From: Zheng Liu <gnehzuil.liu@gmail.com> > > To: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org > > Cc: xiaoqiangnk@gmail.com, achender@linux.vnet.ibm.com, wenqing.lz@taobao.com > > Subject: [RFC][PATCH 09/10 v1][RESEND] ext4: don't need to writeout all dirty > > pages in punch hole > > > > From: Zheng Liu <wenqing.lz@taobao.com> > > > > Now we don't need to writeout all dirty pages when punching a hole. The i_mutex > > locking is taken to avoid concurrent writes. In truncate_pagecache_range, all > > pages in this hole is released, and ext4_es_remove_space is called to update > > extent status tree. > > Hi Zheng, > > I am currently in the middle of reworking punch hole for ext4 so > there will be some changes in this area. See the patch set > > http://www.spinics.net/lists/linux-ext4/msg33014.html Thank you for your reminding. I have seen your patch set and it is pretty cool. IMHO your patch set shall be merged into upstream kernel before applying io tree because io tree still has a lot of things that needs to be done. So I will change it according to your patches. :-) > Moreover I think that we should avoid taking i_mutex if we can and I > believe that we can in this case, because we only need to prevent > allocation. So I just want to let you know that this part is > probably going to change anyway. It seems that we need to take i_mutex locking to prevent from buffered writes after page cache has been truncated by truncate_pagecache_range. If a buffered write without delalloc occurs after truncating page cache and before taking i_data_sem, that means that the allocated block for this buffered write will be removed in ext4_ext_remove_space when the offset is within the range of the hole. Am I missing something? Regards, Zheng > > > > Signed-off-by: Zheng Liu <wenqing.lz@taobao.com> > > --- > > fs/ext4/extents.c | 28 ++++++++++++---------------- > > 1 files changed, 12 insertions(+), 16 deletions(-) > > > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > > index f2c5294..2a526b4 100644 > > --- a/fs/ext4/extents.c > > +++ b/fs/ext4/extents.c > > @@ -4529,9 +4529,11 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > > loff_t first_page_offset, last_page_offset; > > int credits, err = 0; > > > > + mutex_lock(&inode->i_mutex); > > + > > /* No need to punch hole beyond i_size */ > > if (offset >= inode->i_size) > > - return 0; > > + goto error; > > > > /* > > * If the hole extends beyond i_size, set the hole > > @@ -4549,18 +4551,6 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > > first_page_offset = first_page << PAGE_CACHE_SHIFT; > > last_page_offset = last_page << PAGE_CACHE_SHIFT; > > > > - /* > > - * Write out all dirty pages to avoid race conditions > > - * Then release them. > > - */ > > - if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) { > > - err = filemap_write_and_wait_range(mapping, > > - offset, offset + length - 1); > > - > > - if (err) > > - return err; > > - } > > - > > /* Now release the pages */ > > if (last_page_offset > first_page_offset) { > > truncate_pagecache_range(inode, first_page_offset, > > @@ -4572,12 +4562,14 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > > > > credits = ext4_writepage_trans_blocks(inode); > > handle = ext4_journal_start(inode, credits); > > - if (IS_ERR(handle)) > > - return PTR_ERR(handle); > > + if (IS_ERR(handle)) { > > + err = PTR_ERR(handle); > > + goto error; > > + } > > > > err = ext4_orphan_add(handle, inode); > > if (err) > > - goto out; > > + goto error; > > > > /* > > * Now we need to zero out the non-page-aligned data in the > > @@ -4652,6 +4644,8 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > > ext4_ext_invalidate_cache(inode); > > ext4_discard_preallocations(inode); > > > > + err = ext4_es_remove_space(inode, first_block, > > + stop_block - first_block); > > err = ext4_ext_remove_space(inode, first_block, stop_block - 1); > > > > ext4_ext_invalidate_cache(inode); > > @@ -4667,6 +4661,8 @@ out: > > inode->i_mtime = inode->i_ctime = ext4_current_time(inode); > > ext4_mark_inode_dirty(handle, inode); > > ext4_journal_stop(handle); > > +error: > > + mutex_unlock(&inode->i_mutex); > > return err; > > } > > int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, > > -- 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 Mon, 23 Jul 2012, Zheng Liu wrote: > Date: Mon, 23 Jul 2012 19:57:22 +0800 > From: Zheng Liu <gnehzuil.liu@gmail.com> > To: Lukáš Czerner <lczerner@redhat.com> > Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, > xiaoqiangnk@gmail.com, achender@linux.vnet.ibm.com, wenqing.lz@taobao.com > Subject: Re: [RFC][PATCH 09/10 v1][RESEND] ext4: don't need to writeout all > dirty pages in punch hole > > Hi Lukas, > > On Mon, Jul 23, 2012 at 01:01:53PM +0200, Lukáš Czerner wrote: > > On Sun, 22 Jul 2012, Zheng Liu wrote: > > > > > Date: Sun, 22 Jul 2012 15:59:45 +0800 > > > From: Zheng Liu <gnehzuil.liu@gmail.com> > > > To: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org > > > Cc: xiaoqiangnk@gmail.com, achender@linux.vnet.ibm.com, wenqing.lz@taobao.com > > > Subject: [RFC][PATCH 09/10 v1][RESEND] ext4: don't need to writeout all dirty > > > pages in punch hole > > > > > > From: Zheng Liu <wenqing.lz@taobao.com> > > > > > > Now we don't need to writeout all dirty pages when punching a hole. The i_mutex > > > locking is taken to avoid concurrent writes. In truncate_pagecache_range, all > > > pages in this hole is released, and ext4_es_remove_space is called to update > > > extent status tree. > > > > Hi Zheng, > > > > I am currently in the middle of reworking punch hole for ext4 so > > there will be some changes in this area. See the patch set > > > > http://www.spinics.net/lists/linux-ext4/msg33014.html > > Thank you for your reminding. I have seen your patch set and it is > pretty cool. IMHO your patch set shall be merged into upstream kernel > before applying io tree because io tree still has a lot of things that > needs to be done. So I will change it according to your patches. :-) Great, thanks! > > > Moreover I think that we should avoid taking i_mutex if we can and I > > believe that we can in this case, because we only need to prevent > > allocation. So I just want to let you know that this part is > > probably going to change anyway. > > It seems that we need to take i_mutex locking to prevent from buffered > writes after page cache has been truncated by truncate_pagecache_range. > If a buffered write without delalloc occurs after truncating page cache > and before taking i_data_sem, that means that the allocated block for > this buffered write will be removed in ext4_ext_remove_space when the > offset is within the range of the hole. Am I missing something? You're absolutely right, currently this is possible. But I think that we can take i_data_sem before truncating the pagecache hence preventing anyone from mapping new blocks. However this is not yet implemented in my patch set. ... hmm, looking at the ext4_write_begin() it seems like it might not be such good idea after all. It seems to take page lock before i_data_sem so we might get deadlock, moreover if the punch hole happened in the middle of the ext4_write_begin() we might have only part of the data written, moreover this does not have to be hole aligned, which is bad. I need to revise that. Thanks! -Lukas > > Regards, > Zheng > > > > > > > Signed-off-by: Zheng Liu <wenqing.lz@taobao.com> > > > --- > > > fs/ext4/extents.c | 28 ++++++++++++---------------- > > > 1 files changed, 12 insertions(+), 16 deletions(-) > > > > > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > > > index f2c5294..2a526b4 100644 > > > --- a/fs/ext4/extents.c > > > +++ b/fs/ext4/extents.c > > > @@ -4529,9 +4529,11 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > > > loff_t first_page_offset, last_page_offset; > > > int credits, err = 0; > > > > > > + mutex_lock(&inode->i_mutex); > > > + > > > /* No need to punch hole beyond i_size */ > > > if (offset >= inode->i_size) > > > - return 0; > > > + goto error; > > > > > > /* > > > * If the hole extends beyond i_size, set the hole > > > @@ -4549,18 +4551,6 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > > > first_page_offset = first_page << PAGE_CACHE_SHIFT; > > > last_page_offset = last_page << PAGE_CACHE_SHIFT; > > > > > > - /* > > > - * Write out all dirty pages to avoid race conditions > > > - * Then release them. > > > - */ > > > - if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) { > > > - err = filemap_write_and_wait_range(mapping, > > > - offset, offset + length - 1); > > > - > > > - if (err) > > > - return err; > > > - } > > > - > > > /* Now release the pages */ > > > if (last_page_offset > first_page_offset) { > > > truncate_pagecache_range(inode, first_page_offset, > > > @@ -4572,12 +4562,14 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > > > > > > credits = ext4_writepage_trans_blocks(inode); > > > handle = ext4_journal_start(inode, credits); > > > - if (IS_ERR(handle)) > > > - return PTR_ERR(handle); > > > + if (IS_ERR(handle)) { > > > + err = PTR_ERR(handle); > > > + goto error; > > > + } > > > > > > err = ext4_orphan_add(handle, inode); > > > if (err) > > > - goto out; > > > + goto error; > > > > > > /* > > > * Now we need to zero out the non-page-aligned data in the > > > @@ -4652,6 +4644,8 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) > > > ext4_ext_invalidate_cache(inode); > > > ext4_discard_preallocations(inode); > > > > > > + err = ext4_es_remove_space(inode, first_block, > > > + stop_block - first_block); > > > err = ext4_ext_remove_space(inode, first_block, stop_block - 1); > > > > > > ext4_ext_invalidate_cache(inode); > > > @@ -4667,6 +4661,8 @@ out: > > > inode->i_mtime = inode->i_ctime = ext4_current_time(inode); > > > ext4_mark_inode_dirty(handle, inode); > > > ext4_journal_stop(handle); > > > +error: > > > + mutex_unlock(&inode->i_mutex); > > > return err; > > > } > > > int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, > > > > -- > 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 Mon, Jul 23, 2012 at 02:20:57PM +0200, Lukáš Czerner wrote: [cut...] > > > Moreover I think that we should avoid taking i_mutex if we can and I > > > believe that we can in this case, because we only need to prevent > > > allocation. So I just want to let you know that this part is > > > probably going to change anyway. > > > > It seems that we need to take i_mutex locking to prevent from buffered > > writes after page cache has been truncated by truncate_pagecache_range. > > If a buffered write without delalloc occurs after truncating page cache > > and before taking i_data_sem, that means that the allocated block for > > this buffered write will be removed in ext4_ext_remove_space when the > > offset is within the range of the hole. Am I missing something? > > You're absolutely right, currently this is possible. But I think that we > can take i_data_sem before truncating the pagecache hence preventing anyone > from mapping new blocks. However this is not yet implemented in my > patch set. > > ... > hmm, looking at the ext4_write_begin() it seems like it might not be > such good idea after all. It seems to take page lock before > i_data_sem so we might get deadlock, moreover if the punch hole > happened in the middle of the ext4_write_begin() we might have only > part of the data written, moreover this does not have to be hole > aligned, which is bad. I need to revise that. Yes, this is why I think that i_mutex locking should be taken. At least we are safty when we take the i_mutex. :-) 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 f2c5294..2a526b4 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4529,9 +4529,11 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) loff_t first_page_offset, last_page_offset; int credits, err = 0; + mutex_lock(&inode->i_mutex); + /* No need to punch hole beyond i_size */ if (offset >= inode->i_size) - return 0; + goto error; /* * If the hole extends beyond i_size, set the hole @@ -4549,18 +4551,6 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) first_page_offset = first_page << PAGE_CACHE_SHIFT; last_page_offset = last_page << PAGE_CACHE_SHIFT; - /* - * Write out all dirty pages to avoid race conditions - * Then release them. - */ - if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) { - err = filemap_write_and_wait_range(mapping, - offset, offset + length - 1); - - if (err) - return err; - } - /* Now release the pages */ if (last_page_offset > first_page_offset) { truncate_pagecache_range(inode, first_page_offset, @@ -4572,12 +4562,14 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) credits = ext4_writepage_trans_blocks(inode); handle = ext4_journal_start(inode, credits); - if (IS_ERR(handle)) - return PTR_ERR(handle); + if (IS_ERR(handle)) { + err = PTR_ERR(handle); + goto error; + } err = ext4_orphan_add(handle, inode); if (err) - goto out; + goto error; /* * Now we need to zero out the non-page-aligned data in the @@ -4652,6 +4644,8 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) ext4_ext_invalidate_cache(inode); ext4_discard_preallocations(inode); + err = ext4_es_remove_space(inode, first_block, + stop_block - first_block); err = ext4_ext_remove_space(inode, first_block, stop_block - 1); ext4_ext_invalidate_cache(inode); @@ -4667,6 +4661,8 @@ out: inode->i_mtime = inode->i_ctime = ext4_current_time(inode); ext4_mark_inode_dirty(handle, inode); ext4_journal_stop(handle); +error: + mutex_unlock(&inode->i_mutex); return err; } int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,