Filesystems can use this for implementing lseek SEEK_HOLE / SEEK_DATA support via iomap.
Signed-off-by: Andreas Gruenbacher <[email protected]> --- fs/iomap.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/iomap.h | 3 ++ 2 files changed, 92 insertions(+) diff --git a/fs/iomap.c b/fs/iomap.c index 4b10892..781f0a0 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -584,6 +584,95 @@ int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi, } EXPORT_SYMBOL_GPL(iomap_fiemap); +static loff_t +iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length, + void *data, struct iomap *iomap) +{ + if (iomap->type == IOMAP_HOLE) + goto found; + length = iomap->offset + iomap->length - offset; + if (iomap->type != IOMAP_UNWRITTEN) + return length; + offset = page_cache_seek_hole_data(inode, offset, length, SEEK_HOLE); + if (offset < 0) + return length; +found: + *(loff_t *)data = offset; + return 0; +} + +static loff_t +iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length, + void *data, struct iomap *iomap) +{ + if (iomap->type != IOMAP_HOLE && iomap->type != IOMAP_UNWRITTEN) + goto found; + length = iomap->offset + iomap->length - offset; + if (iomap->type != IOMAP_UNWRITTEN) + return length; + offset = page_cache_seek_hole_data(inode, offset, length, SEEK_DATA); + if (offset < 0) + return length; +found: + *(loff_t *)data = offset; + return 0; +} + +/* + * Filesystem helper for lseek SEEK_HOLE / SEEK_DATA. + */ +loff_t +iomap_seek_hole_data(struct inode *inode, loff_t offset, + int whence, const struct iomap_ops *ops) +{ + static loff_t (*actor)(struct inode *, loff_t, loff_t, void *, + struct iomap *); + loff_t size = i_size_read(inode); + loff_t length; + + /* Nothing to be found beyond the end of the file. */ + if (offset >= size) + return -ENXIO; + length = size - offset; + + switch(whence) { + case SEEK_HOLE: + actor = iomap_seek_hole_actor; + break; + + case SEEK_DATA: + actor = iomap_seek_data_actor; + break; + } + + while (length > 0) { + loff_t ret; + + ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops, + &offset, actor); + if (ret <= 0) { + if (ret < 0) + return ret; + break; + } + offset += ret; + length -= ret; + } + + if (length <= 0) { + /* There is an implicit hole at the end of the file. */ + if (whence != SEEK_HOLE) + return -ENXIO; + + /* The last segment can extend beyond the end of the file. */ + if (offset > size) + offset = size; + } + + return offset; +} +EXPORT_SYMBOL_GPL(iomap_seek_hole_data); + /* * Private flags for iomap_dio, must not overlap with the public ones in * iomap.h: diff --git a/include/linux/iomap.h b/include/linux/iomap.h index f753e78..ff89026 100644 --- a/include/linux/iomap.h +++ b/include/linux/iomap.h @@ -83,6 +83,9 @@ int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero, int iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops); int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, loff_t start, loff_t len, const struct iomap_ops *ops); +loff_t iomap_seek_hole_data(struct inode *inode, loff_t offset, + int whence, const struct iomap_ops *ops); + /* * Flags for direct I/O ->end_io: -- 2.7.5
