On Tue, 2022-01-18 at 13:53 +0000, David Howells wrote: > Cachefiles keeps track of how much space is available on the backing > filesystem and refuses new writes permission to start if there isn't enough > (we especially don't want ENOSPC happening). It also tracks the amount of > data pending in DIO writes (cache->b_writing) and reduces the amount of > free space available by this amount before deciding if it can set up a new > write. > > However, the old fscache I/O API was very much page-granularity dependent > and, as such, cachefiles's cache->bshift was meant to be a multiplier to > get from PAGE_SIZE to block size (ie. a blocksize of 512 would give a shift > of 3 for a 4KiB page) - and this was incorrectly being used to turn the > number of bytes in a DIO write into a number of blocks, leading to a > massive over estimation of the amount of data in flight. > > Fix this by changing cache->bshift to be a multiplier from bytes to > blocksize and deal with quantities of blocks, not quantities of pages. > > Fix also the rounding in the calculation in cachefiles_write() which needs > a "- 1" inserting. > > Fixes: 047487c947e8 ("cachefiles: Implement the I/O routines") > Signed-off-by: David Howells <dhowells@xxxxxxxxxx> > cc: linux-cachefs@xxxxxxxxxx > --- > > fs/cachefiles/cache.c | 7 ++----- > fs/cachefiles/internal.h | 2 +- > fs/cachefiles/io.c | 2 +- > 3 files changed, 4 insertions(+), 7 deletions(-) > > diff --git a/fs/cachefiles/cache.c b/fs/cachefiles/cache.c > index ce4d4785003c..1e9c71666c6a 100644 > --- a/fs/cachefiles/cache.c > +++ b/fs/cachefiles/cache.c > @@ -84,9 +84,7 @@ int cachefiles_add_cache(struct cachefiles_cache *cache) > goto error_unsupported; > > cache->bsize = stats.f_bsize; > - cache->bshift = 0; > - if (stats.f_bsize < PAGE_SIZE) > - cache->bshift = PAGE_SHIFT - ilog2(stats.f_bsize); > + cache->bshift = ilog2(stats.f_bsize); > > _debug("blksize %u (shift %u)", > cache->bsize, cache->bshift); > @@ -106,7 +104,6 @@ int cachefiles_add_cache(struct cachefiles_cache *cache) > (unsigned long long) cache->fcull, > (unsigned long long) cache->fstop); > > - stats.f_blocks >>= cache->bshift; > do_div(stats.f_blocks, 100); > cache->bstop = stats.f_blocks * cache->bstop_percent; > cache->bcull = stats.f_blocks * cache->bcull_percent; > @@ -209,7 +206,7 @@ int cachefiles_has_space(struct cachefiles_cache *cache, > return ret; > } > > - b_avail = stats.f_bavail >> cache->bshift; > + b_avail = stats.f_bavail; > b_writing = atomic_long_read(&cache->b_writing); > if (b_avail > b_writing) > b_avail -= b_writing; > diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h > index 8dd54d9375b6..c793d33b0224 100644 > --- a/fs/cachefiles/internal.h > +++ b/fs/cachefiles/internal.h > @@ -86,7 +86,7 @@ struct cachefiles_cache { > unsigned bcull_percent; /* when to start culling (% blocks) */ > unsigned bstop_percent; /* when to stop allocating (% blocks) */ > unsigned bsize; /* cache's block size */ > - unsigned bshift; /* min(ilog2(PAGE_SIZE / bsize), 0) */ > + unsigned bshift; /* ilog2(bsize) */ > uint64_t frun; /* when to stop culling */ > uint64_t fcull; /* when to start culling */ > uint64_t fstop; /* when to stop allocating */ > diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c > index 60b1eac2ce78..04eb52736990 100644 > --- a/fs/cachefiles/io.c > +++ b/fs/cachefiles/io.c > @@ -264,7 +264,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres, > ki->term_func = term_func; > ki->term_func_priv = term_func_priv; > ki->was_async = true; > - ki->b_writing = (len + (1 << cache->bshift)) >> cache->bshift; > + ki->b_writing = (len + (1 << cache->bshift) - 1) >> cache->bshift; > > if (ki->term_func) > ki->iocb.ki_complete = cachefiles_write_complete; > > Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> -- Linux-cachefs mailing list Linux-cachefs@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/linux-cachefs