Dima, please review.
--
Best regards,
Konstantin Khorenko,
Virtuozzo Linux Kernel Team
On 03/13/2016 09:01 PM, Maxim Patlasov wrote:
Long time ago, when ploop used FALLOC_FL_KEEP_SIZE, the logic of
updating io->prealloced_size was implemented correctly:
1) Calculate [pos, end_pos) -- a fragment of image file we're going to
write to.
2) If [pos, end_pos) is beyond end of file (i.e. end_pos > i_size), let's
either simply use preallocated space:
io->prealloced_size -= clu_siz;
or firstly prealloc more space and then use the space:
fallocate(file, mode, pos, prealloc);
io->prealloced_size -= clu_siz;
Now, when ploop doesn't use FALLOC_FL_KEEP_SIZE, the logic above doesn't
work as expected because after prealloc, i_size is extended and the condition
"end_pos > i_size" is false. Hence, a lot of writes to preallocated space
come without "io->prealloced_size -= clu_siz;". And, when all preallocated
space is logically exhausted, io->prealloced_size is still not zero. Then
ploop skips fallocate() and goes to pagecache_write_begin() stuff.
Signed-off-by: Maxim Patlasov <[email protected]>
---
drivers/block/ploop/io_direct.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/drivers/block/ploop/io_direct.c b/drivers/block/ploop/io_direct.c
index cfd7882..3678d5b 100644
--- a/drivers/block/ploop/io_direct.c
+++ b/drivers/block/ploop/io_direct.c
@@ -69,7 +69,7 @@ struct bio_list_walk
static int cached_submit(struct ploop_io *io, iblock_t iblk,
struct ploop_request * preq,
- struct bio_list * sbl, unsigned int size);
+ struct bio_list * sbl, unsigned int size, bool use_prealloc);
static void
dio_submit(struct ploop_io *io, struct ploop_request * preq,
@@ -268,7 +268,7 @@ write_unint:
ploop_add_lockout(preq, 0);
spin_unlock_irq(&preq->plo->lock);
- err = cached_submit(io, iblk, preq, sbl, size);
+ err = cached_submit(io, iblk, preq, sbl, size, false);
goto out;
write_unint_fail:
@@ -362,7 +362,7 @@ static inline void bzero_page(struct page *page)
static int
cached_submit(struct ploop_io *io, iblock_t iblk, struct ploop_request * preq,
- struct bio_list * sbl, unsigned int size)
+ struct bio_list * sbl, unsigned int size, bool use_prealloc)
{
struct ploop_device * plo = preq->plo;
int err = 0;
@@ -370,14 +370,16 @@ cached_submit(struct ploop_io *io, iblock_t iblk, struct
ploop_request * preq,
loff_t clu_siz = 1 << (plo->cluster_log + 9);
struct bio_iter biter;
loff_t new_size;
+ loff_t used_pos;
trace_cached_submit(preq);
pos = (loff_t)iblk << (plo->cluster_log + 9);
end_pos = pos + clu_siz;
+ used_pos = (io->alloc_head - 1) << (io->plo->cluster_log + 9);
#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,24)
- if (end_pos > i_size_read(io->files.inode) &&
+ if (use_prealloc && end_pos > used_pos &&
io->files.file->f_op->fallocate &&
io->files.flags & EXT4_EXTENTS_FL) {
if (unlikely(io->prealloced_size < clu_siz)) {
@@ -701,7 +703,7 @@ dio_submit_alloc(struct ploop_io *io, struct ploop_request
* preq,
return;
}
- err = cached_submit(io, iblk, preq, sbl, size);
+ err = cached_submit(io, iblk, preq, sbl, size, true);
if (err) {
if (err == -ENOSPC)
io->alloc_head--;
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