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author | Jan Kara <jack@suse.com> | 2015-10-22 13:32:21 -0700 |
---|---|---|
committer | Sasha Levin <sasha.levin@oracle.com> | 2015-11-15 12:51:48 -0500 |
commit | f95cfc6a159ca8db816ac4cdb2ad52a0418a1db6 (patch) | |
tree | 4d720ea4c30a19724f10e848183acde48faa2a48 | |
parent | a8b451d26cabcfac073b014feb89dfa23992295c (diff) | |
download | linux-stable-f95cfc6a159ca8db816ac4cdb2ad52a0418a1db6.tar.gz linux-stable-f95cfc6a159ca8db816ac4cdb2ad52a0418a1db6.tar.bz2 linux-stable-f95cfc6a159ca8db816ac4cdb2ad52a0418a1db6.zip |
mm: make sendfile(2) killable
[ Upstream commit 296291cdd1629c308114504b850dc343eabc2782 ]
Currently a simple program below issues a sendfile(2) system call which
takes about 62 days to complete in my test KVM instance.
int fd;
off_t off = 0;
fd = open("file", O_RDWR | O_TRUNC | O_SYNC | O_CREAT, 0644);
ftruncate(fd, 2);
lseek(fd, 0, SEEK_END);
sendfile(fd, fd, &off, 0xfffffff);
Now you should not ask kernel to do a stupid stuff like copying 256MB in
2-byte chunks and call fsync(2) after each chunk but if you do, sysadmin
should have a way to stop you.
We actually do have a check for fatal_signal_pending() in
generic_perform_write() which triggers in this path however because we
always succeed in writing something before the check is done, we return
value > 0 from generic_perform_write() and thus the information about
signal gets lost.
Fix the problem by doing the signal check before writing anything. That
way generic_perform_write() returns -EINTR, the error gets propagated up
and the sendfile loop terminates early.
Signed-off-by: Jan Kara <jack@suse.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
-rw-r--r-- | mm/filemap.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index 37beab98b416..7e6ab98d4d3c 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2489,6 +2489,11 @@ again: break; } + if (fatal_signal_pending(current)) { + status = -EINTR; + break; + } + status = a_ops->write_begin(file, mapping, pos, bytes, flags, &page, &fsdata); if (unlikely(status < 0)) @@ -2526,10 +2531,6 @@ again: written += copied; balance_dirty_pages_ratelimited(mapping); - if (fatal_signal_pending(current)) { - status = -EINTR; - break; - } } while (iov_iter_count(i)); return written ? written : status; |