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fusefs: Fix a bug during VOP_STRATEGY when the server changes file size

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If the FUSE server tells the kernel that a file's size has changed, then
the kernel must invalidate any portion of that file in cache.  But the
kernel can't do that during VOP_STRATEGY, because the file's buffers are
already locked.  Instead, proceed with the write.

PR:		256937
Reported by:	Agata <chogata@moosefs.pro>
Tested by:	Agata <chogata@moosefs.pro>
MFC after:	2 weeks
Reviewed by:	pfg
Differential Revision: https://reviews.freebsd.org/D32332
This commit is contained in:
Alan Somers 2021-10-03 11:51:14 -06:00
parent 7430017b99
commit 032a5bd55b
2 changed files with 93 additions and 7 deletions
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19
sys/fs/fuse/fuse_io.c
View File

@ -1007,13 +1007,18 @@ fuse_io_strategy(struct vnode *vp, struct buf *bp)
/*
* Setup for actual write
*/
error = fuse_vnode_size(vp, &filesize, cred, curthread);
if (error) {
bp->b_ioflags |= BIO_ERROR;
bp->b_error = error;
bufdone(bp);
return (error);
}
/*
* If the file's size is cached, use that value, even if the
* cache is expired. At this point we're already committed to
* writing something. If the FUSE server has changed the
* file's size behind our back, it's too late for us to do
* anything about it. In particular, we can't invalidate any
* part of the file's buffers because VOP_STRATEGY is called
* with them already locked.
*/
filesize = fvdat->cached_attrs.va_size;
/* filesize must've been cached by fuse_vnop_open. */
KASSERT(filesize != VNOVAL, ("filesize should've been cached"));
if ((off_t)bp->b_lblkno * biosize + bp->b_dirtyend > filesize)
bp->b_dirtyend = filesize -

81
tests/sys/fs/fusefs/write.cc
View File

@ -208,6 +208,9 @@ virtual void SetUp() {
}
};
class WriteEofDuringVnopStrategy: public Write, public WithParamInterface<int>
{};
void sigxfsz_handler(int __unused sig) {
Write::s_sigxfsz = 1;
}
@ -526,6 +529,84 @@ TEST_F(Write, eof_during_rmw)
leak(fd);
}
/*
* VOP_STRATEGY should not query the server for the file's size, even if its
* cached attributes have expired.
* Regression test for https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=256937
*/
TEST_P(WriteEofDuringVnopStrategy, eof_during_vop_strategy)
{
const char FULLPATH[] = "mountpoint/some_file.txt";
const char RELPATH[] = "some_file.txt";
Sequence seq;
const off_t filesize = 2 * m_maxbcachebuf;
void *contents;
uint64_t ino = 42;
uint64_t attr_valid = 0;
uint64_t attr_valid_nsec = 0;
mode_t mode = S_IFREG | 0644;
int fd;
int ngetattrs;
ngetattrs = GetParam();
contents = calloc(1, filesize);
EXPECT_LOOKUP(FUSE_ROOT_ID, RELPATH)
.WillRepeatedly(Invoke(
ReturnImmediate([=](auto in __unused, auto& out) {
SET_OUT_HEADER_LEN(out, entry);
out.body.entry.attr.mode = mode;
out.body.entry.nodeid = ino;
out.body.entry.attr.nlink = 1;
out.body.entry.attr.size = filesize;
out.body.entry.attr_valid = attr_valid;
out.body.entry.attr_valid_nsec = attr_valid_nsec;
})));
expect_open(ino, 0, 1);
EXPECT_CALL(*m_mock, process(
ResultOf([=](auto in) {
return (in.header.opcode == FUSE_GETATTR &&
in.header.nodeid == ino);
}, Eq(true)),
_)
).Times(Between(ngetattrs - 1, ngetattrs))
.InSequence(seq)
.WillRepeatedly(Invoke(ReturnImmediate([=](auto i __unused, auto& out) {
SET_OUT_HEADER_LEN(out, attr);
out.body.attr.attr.ino = ino;
out.body.attr.attr.mode = mode;
out.body.attr.attr_valid = attr_valid;
out.body.attr.attr_valid_nsec = attr_valid_nsec;
out.body.attr.attr.size = filesize;
})));
EXPECT_CALL(*m_mock, process(
ResultOf([=](auto in) {
return (in.header.opcode == FUSE_GETATTR &&
in.header.nodeid == ino);
}, Eq(true)),
_)
).InSequence(seq)
.WillRepeatedly(Invoke(ReturnImmediate([=](auto i __unused, auto& out) {
SET_OUT_HEADER_LEN(out, attr);
out.body.attr.attr.ino = ino;
out.body.attr.attr.mode = mode;
out.body.attr.attr_valid = attr_valid;
out.body.attr.attr_valid_nsec = attr_valid_nsec;
out.body.attr.attr.size = filesize / 2;
})));
expect_write(ino, 0, filesize / 2, filesize / 2, contents);
fd = open(FULLPATH, O_RDWR);
ASSERT_LE(0, fd) << strerror(errno);
ASSERT_EQ(filesize / 2, write(fd, contents, filesize / 2))
<< strerror(errno);
}
INSTANTIATE_TEST_CASE_P(W, WriteEofDuringVnopStrategy,
Values(1, 2, 3)
);
/*
* If the kernel cannot be sure which uid, gid, or pid was responsible for a
* write, then it must set the FUSE_WRITE_CACHE bit