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example/passthrough_hp: No auto FOPEN_DIRECT_IO in passthrough mode

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sfs_open and sfs_create set fi->direct_io (FOPEN_DIRECT_IO) when
O_DIRECT is given, in order to benefit from a shared inode lock
in kernel, i.e. to get parallel DIO writes. However, kernel side
disabled passthrough when FOPEN_DIRECT_IO is set. Reads/writes
had been totally failing in this case for O_DIRECT as
sfs_write_buf() and sfs_read() have a sanity check. That sanity
check could be modified, but for performance passthrough is
better than parallel DIO, hence, we only want automatic
FOPEN_DIRECT_IO for O_DIRECT when passthrough is not enabled.

Fixes: https://github.com/libfuse/libfuse/issues/1027

This also fixes automatically switching to FOPEN_DIRECT_IO
for O_DIRECT in sfs_create().
This commit is contained in:
Bernd Schubert 2024-09-12 16:06:09 +02:00 committed by Bernd Schubert
parent 0a76670183
commit c00c9fd831
1 changed files with 27 additions and 22 deletions
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47
example/passthrough_hp.cc
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@ -851,6 +851,28 @@ static void do_passthrough_open(fuse_req_t req, fuse_ino_t ino, int fd,
fi->keep_cache = false;
}
static void sfs_create_open_flags(fuse_file_info *fi)
{
if (fs.direct_io)
fi->direct_io = 1;
/*
* fi->direct_io (FOPEN_DIRECT_IO) is set to benefit from
* parallel_direct_writes, which kernel cannot do for plain O_DIRECT.
* However, passthrough is preferred, but which is not possible when
* FOPEN_DIRECT_IO is set.
*/
if (!fs.passthrough) {
if (fi->flags & O_DIRECT)
fi->direct_io = 1;
}
/* parallel_direct_writes feature depends on direct_io features.
To make parallel_direct_writes valid, need set fi->direct_io
in current function. */
fi->parallel_direct_writes = 1;
}
static void sfs_create(fuse_req_t req, fuse_ino_t parent, const char *name,
mode_t mode, fuse_file_info *fi) {
Inode& inode_p = get_inode(parent);
@ -875,17 +897,12 @@ static void sfs_create(fuse_req_t req, fuse_ino_t parent, const char *name,
return;
}
if (fs.direct_io)
fi->direct_io = 1;
/* parallel_direct_writes feature depends on direct_io features.
To make parallel_direct_writes valid, need set fi->direct_io
in current function. */
fi->parallel_direct_writes = 1;
Inode& inode = get_inode(e.ino);
lock_guard<mutex> g {inode.m};
inode.nopen++;
sfs_create_open_flags(fi);
if (fs.passthrough)
do_passthrough_open(req, e.ino, fd, fi);
fuse_reply_create(req, &e, fi);
@ -942,19 +959,7 @@ static void sfs_open(fuse_req_t req, fuse_ino_t ino, fuse_file_info *fi) {
fi->keep_cache = (fs.timeout != 0);
fi->noflush = (fs.timeout == 0 && (fi->flags & O_ACCMODE) == O_RDONLY);
if (fs.direct_io)
fi->direct_io = 1;
/* Enable direct_io when open has flags O_DIRECT to enjoy the feature
parallel_direct_writes (i.e., to get a shared lock, not exclusive lock,
for writes to the same file). */
if (fi->flags & O_DIRECT)
fi->direct_io = 1;
/* parallel_direct_writes feature depends on direct_io features.
To make parallel_direct_writes valid, need set fi->direct_io
in current function. */
fi->parallel_direct_writes = 1;
sfs_create_open_flags(fi);
fi->fh = fd;
if (fs.passthrough)