On 25-Sep-2014 04:33:36 PM, Matthew Wilcox wrote: > This new function allows us to support hole-punch for DAX files by zeroing > a partial page, as opposed to the dax_truncate_page() function which can > only truncate to the end of the page. Reimplement dax_truncate_page() to > call dax_zero_page_range(). > > Signed-off-by: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx> > [ported to 3.13-rc2] > Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> > --- > Documentation/filesystems/dax.txt | 1 + > fs/dax.c | 36 +++++++++++++++++++++++++++++++----- > include/linux/fs.h | 7 +++++++ > 3 files changed, 39 insertions(+), 5 deletions(-) > > diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt > index 635adaa..ebcd97f 100644 > --- a/Documentation/filesystems/dax.txt > +++ b/Documentation/filesystems/dax.txt > @@ -62,6 +62,7 @@ Filesystem support consists of > for fault and page_mkwrite (which should probably call dax_fault() and > dax_mkwrite(), passing the appropriate get_block() callback) > - calling dax_truncate_page() instead of block_truncate_page() for DAX files > +- calling dax_zero_page_range() instead of zero_user() for DAX files > - ensuring that there is sufficient locking between reads, writes, > truncates and page faults > > diff --git a/fs/dax.c b/fs/dax.c > index 6801be7..91b7561 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -462,13 +462,16 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, > EXPORT_SYMBOL_GPL(dax_fault); > > /** > - * dax_truncate_page - handle a partial page being truncated in a DAX file > + * dax_zero_page_range - zero a range within a page of a DAX file > * @inode: The file being truncated > * @from: The file offset that is being truncated to > + * @length: The number of bytes to zero > * @get_block: The filesystem method used to translate file offsets to blocks > * > - * Similar to block_truncate_page(), this function can be called by a > - * filesystem when it is truncating an DAX file to handle the partial page. > + * This function can be called by a filesystem when it is zeroing part of a > + * page in a DAX file. This is intended for hole-punch operations. If > + * you are truncating a file, the helper function dax_truncate_page() may be > + * more convenient. > * > * We work in terms of PAGE_CACHE_SIZE here for commonality with > * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem > @@ -476,17 +479,18 @@ EXPORT_SYMBOL_GPL(dax_fault); > * block size is smaller than PAGE_SIZE, we have to zero the rest of the page > * since the file might be mmaped. > */ > -int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block) > +int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length, nit: unsigned -> unsigned int ? Do we want a unsigned int or unsigned long here ? > + get_block_t get_block) > { > struct buffer_head bh; > pgoff_t index = from >> PAGE_CACHE_SHIFT; > unsigned offset = from & (PAGE_CACHE_SIZE-1); > - unsigned length = PAGE_CACHE_ALIGN(from) - from; > int err; > > /* Block boundary? Nothing to do */ > if (!length) > return 0; > + BUG_ON((offset + length) > PAGE_CACHE_SIZE); Isn't it a bit extreme to BUG_ON this condition ? We could return an error to the caller, and perhaps WARN_ON_ONCE(), but BUG_ON() appears to be slightly too strong here. > > memset(&bh, 0, sizeof(bh)); > bh.b_size = PAGE_CACHE_SIZE; > @@ -503,4 +507,26 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block) > > return 0; > } > +EXPORT_SYMBOL_GPL(dax_zero_page_range); > + > +/** > + * dax_truncate_page - handle a partial page being truncated in a DAX file > + * @inode: The file being truncated > + * @from: The file offset that is being truncated to > + * @get_block: The filesystem method used to translate file offsets to blocks > + * > + * Similar to block_truncate_page(), this function can be called by a > + * filesystem when it is truncating an DAX file to handle the partial page. an DAX -> a DAX > + * > + * We work in terms of PAGE_CACHE_SIZE here for commonality with > + * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem > + * took care of disposing of the unnecessary blocks. Even if the filesystem > + * block size is smaller than PAGE_SIZE, we have to zero the rest of the page > + * since the file might be mmaped. > + */ > +int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block) > +{ > + unsigned length = PAGE_CACHE_ALIGN(from) - from; unsigned -> unsigned int. Same question about "unsigned long" as above. > + return dax_zero_page_range(inode, from, length, get_block); > +} > EXPORT_SYMBOL_GPL(dax_truncate_page); > diff --git a/include/linux/fs.h b/include/linux/fs.h > index e6b48cc..105d0f0 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -2490,6 +2490,7 @@ extern int nonseekable_open(struct inode * inode, struct file * filp); > > #ifdef CONFIG_FS_DAX > int dax_clear_blocks(struct inode *, sector_t block, long size); > +int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t); > int dax_truncate_page(struct inode *, loff_t from, get_block_t); > ssize_t dax_do_io(int rw, struct kiocb *, struct inode *, struct iov_iter *, > loff_t, get_block_t, dio_iodone_t, int flags); > @@ -2506,6 +2507,12 @@ static inline int dax_truncate_page(struct inode *i, loff_t frm, get_block_t gb) > return 0; > } > > +static inline int dax_zero_page_range(struct inode *i, loff_t frm, > + unsigned len, get_block_t gb) > +{ > + return 0; Should we return 0 or -ENOSYS here ? Thanks, Mathieu > +} > + > static inline ssize_t dax_do_io(int rw, struct kiocb *iocb, > struct inode *inode, struct iov_iter *iter, loff_t pos, > get_block_t get_block, dio_iodone_t end_io, int flags) > -- > 2.1.0 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a> > > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com Key fingerprint: 2A0B 4ED9 15F2 D3FA 45F5 B162 1728 0A97 8118 6ACF -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>