On Tue, 29 Nov 2011 13:33:12 +0800 Cong Wang <amwang@xxxxxxxxxx> wrote: > Systemd needs tmpfs to support fallocate [1], to be able > to safely use mmap(), regarding SIGBUS, on files on the > /dev/shm filesystem. The glibc fallback loop for -ENOSYS > on fallocate is just ugly. > > This patch adds fallocate support to tmpfs, and as we > already have shmem_truncate_range(), it is also easy to > add FALLOC_FL_PUNCH_HOLE support too. > > 1. http://lkml.org/lkml/2011/10/20/275 > one question. > V3->V4: > Handle 'undo' ENOSPC more correctly. > > V2->V3: > a) Read i_size directly after holding i_mutex; > b) Call page_cache_release() too after shmem_getpage(); > c) Undo previous changes when -ENOSPC. > > Cc: Pekka Enberg <penberg@xxxxxxxxxx> > Cc: Christoph Hellwig <hch@xxxxxx> > Cc: Hugh Dickins <hughd@xxxxxxxxxx> > Cc: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> > Cc: Lennart Poettering <lennart@xxxxxxxxxxxxxx> > Cc: Kay Sievers <kay.sievers@xxxxxxxx> > Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > Signed-off-by: WANG Cong <amwang@xxxxxxxxxx> > > --- > mm/shmem.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 files changed, 90 insertions(+), 0 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index d672250..90c835b 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -30,6 +30,7 @@ > #include <linux/mm.h> > #include <linux/export.h> > #include <linux/swap.h> > +#include <linux/falloc.h> > > static struct vfsmount *shm_mnt; > > @@ -1016,6 +1017,35 @@ failed: > return error; > } > > +static void shmem_putpage_noswap(struct inode *inode, pgoff_t index) > +{ > + struct address_space *mapping = inode->i_mapping; > + struct shmem_inode_info *info; > + struct shmem_sb_info *sbinfo; > + struct page *page; > + > + page = find_lock_page(mapping, index); > + You can't know whether the 'page' is allocated by alloc_page() in fallocate() or just found as exiting one. Then, yourwill corrupt existing pages in error path. Is it allowed ? Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>