From 468c09ac43fcea994c4e8827f130bedc2827c625 Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Sat, 21 Jul 2012 10:54:08 +1000 Subject: [PATCH] mm, fadvise: don't return -EINVAL when filesystem cannot implement fadvise() Eric Wong reported his test suite failex when /tmp is tmpfs. https://lkml.org/lkml/2012/2/24/479 Currentlt the input check of POSIX_FADV_WILLNEED has two problems. - requires a_ops->readpage. But in fact, force_page_cache_readahead() requires that the target filesystem has either ->readpage or ->readpages. - returns -EINVAL when the filesystem doesn't have ->readpage. But posix says that fadvise is merely a hint. Thus fadvise() should return 0 if filesystem has no means of implementing fadvise(). The userland application should not know nor care whcih type of filesystem backs the TMPDIR directory, as Eric pointed out. There is nothing which userspace can do to solve this error. So change the return value to 0 when filesytem doesn't support readahead. Signed-off-by: KOSAKI Motohiro Cc: Hugh Dickins Cc: Hillf Danton Signed-off-by: Eric Wong Tested-by: Eric Wong Reviewed-by: Wanlong Gao Signed-off-by: Andrew Morton --- mm/fadvise.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/mm/fadvise.c b/mm/fadvise.c index 469491e0af79..33e6baff72fe 100644 --- a/mm/fadvise.c +++ b/mm/fadvise.c @@ -93,11 +93,6 @@ SYSCALL_DEFINE(fadvise64_64)(int fd, loff_t offset, loff_t len, int advice) spin_unlock(&file->f_lock); break; case POSIX_FADV_WILLNEED: - if (!mapping->a_ops->readpage) { - ret = -EINVAL; - break; - } - /* First and last PARTIAL page! */ start_index = offset >> PAGE_CACHE_SHIFT; end_index = endbyte >> PAGE_CACHE_SHIFT; @@ -106,12 +101,13 @@ SYSCALL_DEFINE(fadvise64_64)(int fd, loff_t offset, loff_t len, int advice) nrpages = end_index - start_index + 1; if (!nrpages) nrpages = ~0UL; - - ret = force_page_cache_readahead(mapping, file, - start_index, - nrpages); - if (ret > 0) - ret = 0; + + /* + * Ignore return value because fadvise() shall return + * success even if filesystem can't retrieve a hint, + */ + force_page_cache_readahead(mapping, file, start_index, + nrpages); break; case POSIX_FADV_NOREUSE: break; -- 2.39.5