diff options
| author | David Howells <dhowells@redhat.com> | 2021-11-05 13:36:49 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-11-06 13:30:34 -0700 |
| commit | 8c8387ee3f55a38c3388882f1dd72dc526965211 (patch) | |
| tree | 9fc8dceb13c73dd91dda02df30d656945a6631c7 /mm/filemap.c | |
| parent | d1fea155ee3d90fb3adcb3d6c42751860be3b158 (diff) | |
mm: stop filemap_read() from grabbing a superfluous page
Under some circumstances, filemap_read() will allocate sufficient pages
to read to the end of the file, call readahead/readpages on them and
copy the data over - and then it will allocate another page at the EOF
and call readpage on that and then ignore it. This is unnecessary and a
waste of time and resources.
filemap_read() *does* check for this, but only after it has already done
the allocation and I/O. Fix this by checking before calling
filemap_get_pages() also.
Link: https://lkml.kernel.org/r/163472463105.3126792.7056099385135786492.stgit@warthog.procyon.org.uk
Link: https://lore.kernel.org/r/160588481358.3465195.16552616179674485179.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/163456863216.2614702.6384850026368833133.stgit@warthog.procyon.org.uk/
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/filemap.c')
| -rw-r--r-- | mm/filemap.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index dae481293b5d..e50be519f6a4 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2625,6 +2625,9 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter, if ((iocb->ki_flags & IOCB_WAITQ) && already_read) iocb->ki_flags |= IOCB_NOWAIT; + if (unlikely(iocb->ki_pos >= i_size_read(inode))) + break; + error = filemap_get_pages(iocb, iter, &pvec); if (error < 0) break; |