diff options
| author | Goldwyn Rodrigues | 2019-10-18 16:44:10 -0700 |
|---|---|---|
| committer | Darrick J. Wong | 2019-10-21 08:51:59 -0700 |
| commit | c039b99792726346ad46ff17c5a5bcb77a5edac4 (patch) | |
| tree | e9034adc21c6fc3ad6fc775e8f3225e35b015d50 /fs/iomap/apply.c | |
| parent | eb81cf9d0e18d438e27339e0d1a49d3ac8644674 (diff) | |
iomap: use a srcmap for a read-modify-write I/O
The srcmap is used to identify where the read is to be performed from.
It is passed to ->iomap_begin, which can fill it in if we need to read
data for partially written blocks from a different location than the
write target. The srcmap is only supported for buffered writes so far.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
[hch: merged two patches, removed the IOMAP_F_COW flag, use iomap as
srcmap if not set, adjust length down to srcmap end as well]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Diffstat (limited to 'fs/iomap/apply.c')
| -rw-r--r-- | fs/iomap/apply.c | 25 |
1 files changed, 19 insertions, 6 deletions
diff --git a/fs/iomap/apply.c b/fs/iomap/apply.c index 54c02aecf3cd..484dd8eda861 100644 --- a/fs/iomap/apply.c +++ b/fs/iomap/apply.c @@ -23,8 +23,10 @@ loff_t iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags, const struct iomap_ops *ops, void *data, iomap_actor_t actor) { - struct iomap iomap = { 0 }; + struct iomap iomap = { .type = IOMAP_HOLE }; + struct iomap srcmap = { .type = IOMAP_HOLE }; loff_t written = 0, ret; + u64 end; /* * Need to map a range from start position for length bytes. This can @@ -38,7 +40,7 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags, * expose transient stale data. If the reserve fails, we can safely * back out at this point as there is nothing to undo. */ - ret = ops->iomap_begin(inode, pos, length, flags, &iomap); + ret = ops->iomap_begin(inode, pos, length, flags, &iomap, &srcmap); if (ret) return ret; if (WARN_ON(iomap.offset > pos)) @@ -50,15 +52,26 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags, * Cut down the length to the one actually provided by the filesystem, * as it might not be able to give us the whole size that we requested. */ - if (iomap.offset + iomap.length < pos + length) - length = iomap.offset + iomap.length - pos; + end = iomap.offset + iomap.length; + if (srcmap.type != IOMAP_HOLE) + end = min(end, srcmap.offset + srcmap.length); + if (pos + length > end) + length = end - pos; /* - * Now that we have guaranteed that the space allocation will succeed. + * Now that we have guaranteed that the space allocation will succeed, * we can do the copy-in page by page without having to worry about * failures exposing transient data. + * + * To support COW operations, we read in data for partially blocks from + * the srcmap if the file system filled it in. In that case we the + * length needs to be limited to the earlier of the ends of the iomaps. + * If the file system did not provide a srcmap we pass in the normal + * iomap into the actors so that they don't need to have special + * handling for the two cases. */ - written = actor(inode, pos, length, data, &iomap); + written = actor(inode, pos, length, data, &iomap, + srcmap.type != IOMAP_HOLE ? &srcmap : &iomap); /* * Now the data has been copied, commit the range we've copied. This |