| Message ID | a01641c22af0856fa2b19ab00a6660706056666d.1714046808.git.ritesh.list@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | ext2 iomap changes and iomap improvements | expand |
On Thu, Apr 25, 2024 at 06:58:50PM +0530, Ritesh Harjani (IBM) wrote: > +static loff_t iomap_read_folio_iter(const struct iomap_iter *iter, > + struct iomap_readpage_ctx *ctx) > +{ > + struct folio *folio = ctx->cur_folio; > + size_t pos = offset_in_folio(folio, iter->pos); "pos" is position in file. You should call this 'offset'. > + loff_t length = min_t(loff_t, folio_size(folio) - pos, > + iomap_length(iter)); > + loff_t done, ret; > + > + for (done = 0; done < length; done += ret) { > + ret = iomap_readpage_iter(iter, ctx, done); > + if (ret <= 0) > + return ret; > + }
On Thu, Apr 25, 2024 at 06:58:50PM +0530, Ritesh Harjani (IBM) wrote: > iomap_readpage_iter() handles "uptodate blocks" and "not uptodate blocks" > within a folio separately. This makes iomap_read_folio() to call into > ->iomap_begin() to request for extent mapping even though it might already > have an extent which is not fully processed. > > This happens when we either have a large folio or with bs < ps. In these > cases we can have sub blocks which can be uptodate (say for e.g. due to > previous writes). With iomap_read_folio_iter(), this is handled more > efficiently by not calling ->iomap_begin() call until all the sub blocks > with the current folio are processed. Maybe throw in a sentence here that this copies what iomap_readahead_iter already does? Otherwise this looks good to me modulo the offset comment from willy.
Christoph Hellwig <hch@infradead.org> writes: > On Thu, Apr 25, 2024 at 06:58:50PM +0530, Ritesh Harjani (IBM) wrote: >> iomap_readpage_iter() handles "uptodate blocks" and "not uptodate blocks" >> within a folio separately. This makes iomap_read_folio() to call into >> ->iomap_begin() to request for extent mapping even though it might already >> have an extent which is not fully processed. >> >> This happens when we either have a large folio or with bs < ps. In these >> cases we can have sub blocks which can be uptodate (say for e.g. due to >> previous writes). With iomap_read_folio_iter(), this is handled more >> efficiently by not calling ->iomap_begin() call until all the sub blocks >> with the current folio are processed. > > Maybe throw in a sentence here that this copies what > iomap_readahead_iter already does? Does this sound any better? iomap_read_folio_iter() handles multiple sub blocks within a given folio but it's implementation logic is similar to how iomap_readahead_iter() handles multiple folios within a single mapped extent. Both of them iterate over a given range of folio/mapped extent and call iomap_readpage_iter() for reading. > > Otherwise this looks good to me modulo the offset comment from willy. Yes, I will address willy's comment too. Thanks for the review! -ritesh
On Fri, Apr 26, 2024 at 02:20:05PM +0530, Ritesh Harjani wrote: > iomap_read_folio_iter() handles multiple sub blocks within a given > folio but it's implementation logic is similar to how > iomap_readahead_iter() handles multiple folios within a single mapped > extent. Both of them iterate over a given range of folio/mapped extent > and call iomap_readpage_iter() for reading. Sounds good.
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index 9f79c82d1f73..0a4269095ae2 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -444,6 +444,24 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter, return pos - orig_pos + plen; } +static loff_t iomap_read_folio_iter(const struct iomap_iter *iter, + struct iomap_readpage_ctx *ctx) +{ + struct folio *folio = ctx->cur_folio; + size_t pos = offset_in_folio(folio, iter->pos); + loff_t length = min_t(loff_t, folio_size(folio) - pos, + iomap_length(iter)); + loff_t done, ret; + + for (done = 0; done < length; done += ret) { + ret = iomap_readpage_iter(iter, ctx, done); + if (ret <= 0) + return ret; + } + + return done; +} + int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops) { struct iomap_iter iter = { @@ -459,7 +477,7 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops) trace_iomap_readpage(iter.inode, 1); while ((ret = iomap_iter(&iter, ops)) > 0) - iter.processed = iomap_readpage_iter(&iter, &ctx, 0); + iter.processed = iomap_read_folio_iter(&iter, &ctx); if (ret < 0) folio_set_error(folio);
iomap_readpage_iter() handles "uptodate blocks" and "not uptodate blocks" within a folio separately. This makes iomap_read_folio() to call into ->iomap_begin() to request for extent mapping even though it might already have an extent which is not fully processed. This happens when we either have a large folio or with bs < ps. In these cases we can have sub blocks which can be uptodate (say for e.g. due to previous writes). With iomap_read_folio_iter(), this is handled more efficiently by not calling ->iomap_begin() call until all the sub blocks with the current folio are processed. Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> cc: Ojaswin Mujoo <ojaswin@linux.ibm.com> --- fs/iomap/buffered-io.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-)