Some filesystems like erofs/reiserfs have the ability to pack tail data into metadata, however iomap framework can only support mapping inline data with IOMAP_INLINE type, it restricts that: - inline data should be locating at page #0. - inline size should equal to .i_size So we can not use IOMAP_INLINE to handle tail-packing case.
This patch introduces new mapping type IOMAP_TAIL to map tail-packed data for further use of erofs. Signed-off-by: Chao Yu <[email protected]> --- fs/iomap.c | 22 ++++++++++++++++++++++ include/linux/iomap.h | 1 + 2 files changed, 23 insertions(+) diff --git a/fs/iomap.c b/fs/iomap.c index 12654c2e78f8..ae7777ce77d0 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -280,6 +280,23 @@ iomap_read_inline_data(struct inode *inode, struct page *page, SetPageUptodate(page); } +static void +iomap_read_tail_data(struct inode *inode, struct page *page, + struct iomap *iomap) +{ + size_t size = i_size_read(inode) & (PAGE_SIZE - 1); + void *addr; + + if (PageUptodate(page)) + return; + + addr = kmap_atomic(page); + memcpy(addr, iomap->inline_data, size); + memset(addr + size, 0, PAGE_SIZE - size); + kunmap_atomic(addr); + SetPageUptodate(page); +} + static loff_t iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data, struct iomap *iomap) @@ -298,6 +315,11 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data, return PAGE_SIZE; } + if (iomap->type == IOMAP_TAIL) { + iomap_read_tail_data(inode, page, iomap); + return PAGE_SIZE; + } + /* zero post-eof blocks as the page may be mapped */ iomap_adjust_read_range(inode, iop, &pos, length, &poff, &plen); if (plen == 0) diff --git a/include/linux/iomap.h b/include/linux/iomap.h index 2103b94cb1bf..7e1ee48e3db7 100644 --- a/include/linux/iomap.h +++ b/include/linux/iomap.h @@ -25,6 +25,7 @@ struct vm_fault; #define IOMAP_MAPPED 0x03 /* blocks allocated at @addr */ #define IOMAP_UNWRITTEN 0x04 /* blocks allocated at @addr in unwritten state */ #define IOMAP_INLINE 0x05 /* data inline in the inode */ +#define IOMAP_TAIL 0x06 /* tail data packed in metdata */ /* * Flags for all iomap mappings: -- 2.18.0.rc1
