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b5aaf286ea
freebsd-dev/sys/fs/fuse/fuse_io.c
Alan Somers b5aaf286ea fusefs: fix the "write-through" of write-through cacheing 
Our fusefs(5) module supports three cache modes: uncached, write-through,
and write-back.  However, the write-through mode (which is the default) has
never actually worked as its name suggests.  Rather, it's always been more
like "write-around".  It wrote directly, bypassing the cache.  The cache
would only be populated by a subsequent read of the same data.

This commit fixes that problem.  Now the write-through mode works as one
would expect: write(2) immediately adds data to the cache and then blocks
while the daemon processes the write operation.

A side effect of this change is that non-cache-block-aligned writes will now
incur a read-modify-write cycle of the cache block.  The old behavior
(bypassing write cache entirely) can still be achieved by opening a file
with O_DIRECT.

PR:		237588
Sponsored by:	The FreeBSD Foundation
2019-06-14 19:47:48 +00:00

1021 lines
29 KiB
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/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 2007-2009 Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Copyright (C) 2005 Csaba Henk.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/module.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/uio.h>
#include <sys/malloc.h>
#include <sys/queue.h>
#include <sys/lock.h>
#include <sys/sx.h>
#include <sys/mutex.h>
#include <sys/rwlock.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/stat.h>
#include <sys/unistd.h>
#include <sys/filedesc.h>
#include <sys/file.h>
#include <sys/fcntl.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/sysctl.h>
#include <sys/vmmeter.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_page.h>
#include <vm/vm_object.h>
#include "fuse.h"
#include "fuse_file.h"
#include "fuse_node.h"
#include "fuse_internal.h"
#include "fuse_ipc.h"
#include "fuse_io.h"
SDT_PROVIDER_DECLARE(fusefs);
/*
* Fuse trace probe:
* arg0: verbosity. Higher numbers give more verbose messages
* arg1: Textual message
*/
SDT_PROBE_DEFINE2(fusefs, , io, trace, "int", "char*");
static void
fuse_io_clear_suid_on_write(struct vnode *vp, struct ucred *cred,
struct thread *td);
static int
fuse_read_directbackend(struct vnode *vp, struct uio *uio,
struct ucred *cred, struct fuse_filehandle *fufh);
static int
fuse_read_biobackend(struct vnode *vp, struct uio *uio, int ioflag,
struct ucred *cred, struct fuse_filehandle *fufh, pid_t pid);
static int
fuse_write_directbackend(struct vnode *vp, struct uio *uio,
struct ucred *cred, struct fuse_filehandle *fufh, off_t filesize,
int ioflag, bool pages);
static int
fuse_write_biobackend(struct vnode *vp, struct uio *uio,
struct ucred *cred, struct fuse_filehandle *fufh, int ioflag, pid_t pid);
/*
* FreeBSD clears the SUID and SGID bits on any write by a non-root user.
*/
static void
fuse_io_clear_suid_on_write(struct vnode *vp, struct ucred *cred,
struct thread *td)
{
struct fuse_data *data;
struct mount *mp;
struct vattr va;
int dataflags;
mp = vnode_mount(vp);
data = fuse_get_mpdata(mp);
dataflags = data->dataflags;
if (dataflags & FSESS_DEFAULT_PERMISSIONS) {
if (priv_check_cred(cred, PRIV_VFS_RETAINSUGID)) {
fuse_internal_getattr(vp, &va, cred, td);
if (va.va_mode & (S_ISUID | S_ISGID)) {
mode_t mode = va.va_mode & ~(S_ISUID | S_ISGID);
/* Clear all vattr fields except mode */
vattr_null(&va);
va.va_mode = mode;
/*
* Ignore fuse_internal_setattr's return value,
* because at this point the write operation has
* already succeeded and we don't want to return
* failing status for that.
*/
(void)fuse_internal_setattr(vp, &va, td, NULL);
}
}
}
}
SDT_PROBE_DEFINE5(fusefs, , io, io_dispatch, "struct vnode*", "struct uio*",
"int", "struct ucred*", "struct fuse_filehandle*");
int
fuse_io_dispatch(struct vnode *vp, struct uio *uio, int ioflag, bool pages,
struct ucred *cred, pid_t pid)
{
struct fuse_filehandle *fufh;
int err, directio;
int fflag;
bool closefufh = false;
MPASS(vp->v_type == VREG || vp->v_type == VDIR);
fflag = (uio->uio_rw == UIO_READ) ? FREAD : FWRITE;
err = fuse_filehandle_getrw(vp, fflag, &fufh, cred, pid);
if (err == EBADF && vnode_mount(vp)->mnt_flag & MNT_EXPORTED) {
/*
* nfsd will do I/O without first doing VOP_OPEN. We
* must implicitly open the file here
*/
err = fuse_filehandle_open(vp, fflag, &fufh, curthread, cred);
closefufh = true;
}
else if (err) {
printf("FUSE: io dispatch: filehandles are closed\n");
return err;
}
if (err)
goto out;
SDT_PROBE5(fusefs, , io, io_dispatch, vp, uio, ioflag, cred, fufh);
/*
* Ideally, when the daemon asks for direct io at open time, the
* standard file flag should be set according to this, so that would
* just change the default mode, which later on could be changed via
* fcntl(2).
* But this doesn't work, the O_DIRECT flag gets cleared at some point
* (don't know where). So to make any use of the Fuse direct_io option,
* we hardwire it into the file's private data (similarly to Linux,
* btw.).
*/
directio = (ioflag & IO_DIRECT) || !fsess_opt_datacache(vnode_mount(vp));
switch (uio->uio_rw) {
case UIO_READ:
if (directio) {
SDT_PROBE2(fusefs, , io, trace, 1,
"direct read of vnode");
err = fuse_read_directbackend(vp, uio, cred, fufh);
} else {
SDT_PROBE2(fusefs, , io, trace, 1,
"buffered read of vnode");
err = fuse_read_biobackend(vp, uio, ioflag, cred, fufh,
pid);
}
break;
case UIO_WRITE:
if (directio) {
const int iosize = fuse_iosize(vp);
off_t start, end, filesize;
SDT_PROBE2(fusefs, , io, trace, 1,
"direct write of vnode");
err = fuse_vnode_size(vp, &filesize, cred, curthread);
if (err)
goto out;
start = uio->uio_offset;
end = start + uio->uio_resid;
/*
* Invalidate the write cache unless we're coming from
* VOP_PUTPAGES, in which case we're writing _from_ the
* write cache
*/
if (!pages )
v_inval_buf_range(vp, start, end, iosize);
err = fuse_write_directbackend(vp, uio, cred, fufh,
filesize, ioflag, pages);
} else {
SDT_PROBE2(fusefs, , io, trace, 1,
"buffered write of vnode");
if (fuse_data_cache_mode == FUSE_CACHE_WT)
ioflag |= IO_SYNC;
err = fuse_write_biobackend(vp, uio, cred, fufh, ioflag,
pid);
}
fuse_io_clear_suid_on_write(vp, cred, uio->uio_td);
break;
default:
panic("uninterpreted mode passed to fuse_io_dispatch");
}
out:
if (closefufh)
fuse_filehandle_close(vp, fufh, curthread, cred);
return (err);
}
SDT_PROBE_DEFINE4(fusefs, , io, read_bio_backend_start, "int", "int", "int", "int");
SDT_PROBE_DEFINE2(fusefs, , io, read_bio_backend_feed, "int", "struct buf*");
SDT_PROBE_DEFINE4(fusefs, , io, read_bio_backend_end, "int", "ssize_t", "int",
"struct buf*");
static int
fuse_read_biobackend(struct vnode *vp, struct uio *uio, int ioflag,
struct ucred *cred, struct fuse_filehandle *fufh, pid_t pid)
{
struct buf *bp;
daddr_t lbn;
int bcount;
int err, n = 0, on = 0;
off_t filesize;
const int biosize = fuse_iosize(vp);
if (uio->uio_offset < 0)
return (EINVAL);
err = fuse_vnode_size(vp, &filesize, cred, curthread);
if (err)
return err;
for (err = 0, bp = NULL; uio->uio_resid > 0; bp = NULL) {
if (fuse_isdeadfs(vp)) {
err = ENXIO;
break;
}
if (filesize - uio->uio_offset <= 0)
break;
lbn = uio->uio_offset / biosize;
on = uio->uio_offset & (biosize - 1);
if ((off_t)lbn * biosize >= filesize) {
bcount = 0;
} else if ((off_t)(lbn + 1) * biosize > filesize) {
bcount = filesize - (off_t)lbn *biosize;
} else {
bcount = biosize;
}
SDT_PROBE4(fusefs, , io, read_bio_backend_start,
biosize, (int)lbn, on, bcount);
/* TODO: readahead. See ext2_read for an example */
err = bread(vp, lbn, bcount, NOCRED, &bp);
if (err) {
brelse(bp);
bp = NULL;
break;
}
/*
* on is the offset into the current bp. Figure out how many
* bytes we can copy out of the bp. Note that bcount is
* NOT DEV_BSIZE aligned.
*
* Then figure out how many bytes we can copy into the uio.
*/
n = 0;
if (on < bcount)
n = MIN((unsigned)(bcount - on), uio->uio_resid);
if (n > 0) {
SDT_PROBE2(fusefs, , io, read_bio_backend_feed, n, bp);
err = uiomove(bp->b_data + on, n, uio);
}
vfs_bio_brelse(bp, ioflag);
SDT_PROBE4(fusefs, , io, read_bio_backend_end, err,
uio->uio_resid, n, bp);
}
return (err);
}
SDT_PROBE_DEFINE1(fusefs, , io, read_directbackend_start,
"struct fuse_read_in*");
SDT_PROBE_DEFINE3(fusefs, , io, read_directbackend_complete,
"struct fuse_dispatcher*", "struct fuse_read_in*", "struct uio*");
static int
fuse_read_directbackend(struct vnode *vp, struct uio *uio,
struct ucred *cred, struct fuse_filehandle *fufh)
{
struct fuse_data *data;
struct fuse_dispatcher fdi;
struct fuse_read_in *fri;
int err = 0;
data = fuse_get_mpdata(vp->v_mount);
if (uio->uio_resid == 0)
return (0);
fdisp_init(&fdi, 0);
/*
* XXX In "normal" case we use an intermediate kernel buffer for
* transmitting data from daemon's context to ours. Eventually, we should
* get rid of this. Anyway, if the target uio lives in sysspace (we are
* called from pageops), and the input data doesn't need kernel-side
* processing (we are not called from readdir) we can already invoke
* an optimized, "peer-to-peer" I/O routine.
*/
while (uio->uio_resid > 0) {
fdi.iosize = sizeof(*fri);
fdisp_make_vp(&fdi, FUSE_READ, vp, uio->uio_td, cred);
fri = fdi.indata;
fri->fh = fufh->fh_id;
fri->offset = uio->uio_offset;
fri->size = MIN(uio->uio_resid,
fuse_get_mpdata(vp->v_mount)->max_read);
if (fuse_libabi_geq(data, 7, 9)) {
/* See comment regarding FUSE_WRITE_LOCKOWNER */
fri->read_flags = 0;
fri->flags = fufh_type_2_fflags(fufh->fufh_type);
}
SDT_PROBE1(fusefs, , io, read_directbackend_start, fri);
if ((err = fdisp_wait_answ(&fdi)))
goto out;
SDT_PROBE3(fusefs, , io, read_directbackend_complete,
&fdi, fri, uio);
if ((err = uiomove(fdi.answ, MIN(fri->size, fdi.iosize), uio)))
break;
if (fdi.iosize < fri->size)
break;
}
out:
fdisp_destroy(&fdi);
return (err);
}
static int
fuse_write_directbackend(struct vnode *vp, struct uio *uio,
struct ucred *cred, struct fuse_filehandle *fufh, off_t filesize,
int ioflag, bool pages)
{
struct fuse_vnode_data *fvdat = VTOFUD(vp);
struct fuse_data *data;
struct fuse_write_in *fwi;
struct fuse_write_out *fwo;
struct fuse_dispatcher fdi;
size_t chunksize;
void *fwi_data;
off_t as_written_offset;
int diff;
int err = 0;
bool direct_io = fufh->fuse_open_flags & FOPEN_DIRECT_IO;
uint32_t write_flags;
data = fuse_get_mpdata(vp->v_mount);
/*
* Don't set FUSE_WRITE_LOCKOWNER in write_flags. It can't be set
* accurately when using POSIX AIO, libfuse doesn't use it, and I'm not
* aware of any file systems that do. It was an attempt to add
* Linux-style mandatory locking to the FUSE protocol, but mandatory
* locking is deprecated even on Linux. See Linux commit
* f33321141b273d60cbb3a8f56a5489baad82ba5e .
*/
/*
* Set FUSE_WRITE_CACHE whenever we don't know the uid, gid, and/or pid
* that originated a write. For example when writing from the
* writeback cache. I don't know of a single file system that cares,
* but the protocol says we're supposed to do this.
*/
write_flags = !pages && (
(ioflag & IO_DIRECT) ||
!fsess_opt_datacache(vnode_mount(vp)) ||
fuse_data_cache_mode != FUSE_CACHE_WB) ? 0 : FUSE_WRITE_CACHE;
if (uio->uio_resid == 0)
return (0);
if (ioflag & IO_APPEND)
uio_setoffset(uio, filesize);
if (vn_rlimit_fsize(vp, uio, uio->uio_td))
return (EFBIG);
fdisp_init(&fdi, 0);
while (uio->uio_resid > 0) {
chunksize = MIN(uio->uio_resid, data->max_write);
fdi.iosize = sizeof(*fwi) + chunksize;
fdisp_make_vp(&fdi, FUSE_WRITE, vp, uio->uio_td, cred);
fwi = fdi.indata;
fwi->fh = fufh->fh_id;
fwi->offset = uio->uio_offset;
fwi->size = chunksize;
fwi->write_flags = write_flags;
if (fuse_libabi_geq(data, 7, 9)) {
fwi->flags = fufh_type_2_fflags(fufh->fufh_type);
fwi_data = (char *)fdi.indata + sizeof(*fwi);
} else {
fwi_data = (char *)fdi.indata +
FUSE_COMPAT_WRITE_IN_SIZE;
}
if ((err = uiomove(fwi_data, chunksize, uio)))
break;
retry:
err = fdisp_wait_answ(&fdi);
if (err == ERESTART || err == EINTR || err == EWOULDBLOCK) {
/*
* Rewind the uio so dofilewrite will know it's
* incomplete
*/
uio->uio_resid += fwi->size;
uio->uio_offset -= fwi->size;
/*
* Change ERESTART into EINTR because we can't rewind
* uio->uio_iov. Basically, once uiomove(9) has been
* called, it's impossible to restart a syscall.
*/
if (err == ERESTART)
err = EINTR;
break;
} else if (err) {
break;
}
fwo = ((struct fuse_write_out *)fdi.answ);
/* Adjust the uio in the case of short writes */
diff = fwi->size - fwo->size;
as_written_offset = uio->uio_offset - diff;
if (as_written_offset - diff > filesize &&
fuse_data_cache_mode != FUSE_CACHE_UC)
fuse_vnode_setsize(vp, as_written_offset);
if (as_written_offset - diff >= filesize)
fvdat->flag &= ~FN_SIZECHANGE;
if (diff < 0) {
printf("WARNING: misbehaving FUSE filesystem "
"wrote more data than we provided it\n");
err = EINVAL;
break;
} else if (diff > 0) {
/* Short write */
if (!direct_io) {
printf("WARNING: misbehaving FUSE filesystem: "
"short writes are only allowed with "
"direct_io\n");
}
if (ioflag & IO_DIRECT) {
/* Return early */
uio->uio_resid += diff;
uio->uio_offset -= diff;
break;
} else {
/* Resend the unwritten portion of data */
fdi.iosize = sizeof(*fwi) + diff;
/* Refresh fdi without clearing data buffer */
fdisp_refresh_vp(&fdi, FUSE_WRITE, vp,
uio->uio_td, cred);
fwi = fdi.indata;
MPASS2(fwi == fdi.indata, "FUSE dispatcher "
"reallocated despite no increase in "
"size?");
void *src = (char*)fwi_data + fwo->size;
memmove(fwi_data, src, diff);
fwi->fh = fufh->fh_id;
fwi->offset = as_written_offset;
fwi->size = diff;
fwi->write_flags = write_flags;
goto retry;
}
}
}
fdisp_destroy(&fdi);
return (err);
}
SDT_PROBE_DEFINE6(fusefs, , io, write_biobackend_start, "int64_t", "int", "int",
"struct uio*", "int", "bool");
SDT_PROBE_DEFINE2(fusefs, , io, write_biobackend_append_race, "long", "int");
SDT_PROBE_DEFINE2(fusefs, , io, write_biobackend_issue, "int", "struct buf*");
static int
fuse_write_biobackend(struct vnode *vp, struct uio *uio,
struct ucred *cred, struct fuse_filehandle *fufh, int ioflag, pid_t pid)
{
struct fuse_vnode_data *fvdat = VTOFUD(vp);
struct buf *bp;
daddr_t lbn;
off_t filesize;
int bcount;
int n, on, seqcount, err = 0;
bool last_page;
const int biosize = fuse_iosize(vp);
seqcount = ioflag >> IO_SEQSHIFT;
KASSERT(uio->uio_rw == UIO_WRITE, ("fuse_write_biobackend mode"));
if (vp->v_type != VREG)
return (EIO);
if (uio->uio_offset < 0)
return (EINVAL);
if (uio->uio_resid == 0)
return (0);
err = fuse_vnode_size(vp, &filesize, cred, curthread);
if (err)
return err;
if (ioflag & IO_APPEND)
uio_setoffset(uio, filesize);
if (vn_rlimit_fsize(vp, uio, uio->uio_td))
return (EFBIG);
do {
bool direct_append, extending;
if (fuse_isdeadfs(vp)) {
err = ENXIO;
break;
}
lbn = uio->uio_offset / biosize;
on = uio->uio_offset & (biosize - 1);
n = MIN((unsigned)(biosize - on), uio->uio_resid);
again:
/* Get or create a buffer for the write */
direct_append = uio->uio_offset == filesize && n;
if (uio->uio_offset + n < filesize) {
extending = false;
if ((off_t)(lbn + 1) * biosize < filesize) {
/* Not the file's last block */
bcount = biosize;
} else {
/* The file's last block */
bcount = filesize - (off_t)lbn * biosize;
}
} else {
extending = true;
bcount = on + n;
}
if (howmany(((off_t)lbn * biosize + on + n - 1), PAGE_SIZE) >=
howmany(filesize, PAGE_SIZE))
last_page = true;
else
last_page = false;
if (direct_append) {
/*
* Take care to preserve the buffer's B_CACHE state so
* as not to cause an unnecessary read.
*/
bp = getblk(vp, lbn, on, PCATCH, 0, 0);
if (bp != NULL) {
uint32_t save = bp->b_flags & B_CACHE;
allocbuf(bp, bcount);
bp->b_flags |= save;
}
} else {
bp = getblk(vp, lbn, bcount, PCATCH, 0, 0);
}
if (!bp) {
err = EINTR;
break;
}
if (extending) {
/*
* Extend file _after_ locking buffer so we won't race
* with other readers
*/
err = fuse_vnode_setsize(vp, uio->uio_offset + n);
filesize = uio->uio_offset + n;
fvdat->flag |= FN_SIZECHANGE;
if (err) {
brelse(bp);
break;
}
}
SDT_PROBE6(fusefs, , io, write_biobackend_start,
lbn, on, n, uio, bcount, direct_append);
/*
* Issue a READ if B_CACHE is not set. In special-append
* mode, B_CACHE is based on the buffer prior to the write
* op and is typically set, avoiding the read. If a read
* is required in special append mode, the server will
* probably send us a short-read since we extended the file
* on our end, resulting in b_resid == 0 and, thusly,
* B_CACHE getting set.
*
* We can also avoid issuing the read if the write covers
* the entire buffer. We have to make sure the buffer state
* is reasonable in this case since we will not be initiating
* I/O. See the comments in kern/vfs_bio.c's getblk() for
* more information.
*
* B_CACHE may also be set due to the buffer being cached
* normally.
*/
if (on == 0 && n == bcount) {
bp->b_flags |= B_CACHE;
bp->b_flags &= ~B_INVAL;
bp->b_ioflags &= ~BIO_ERROR;
}
if ((bp->b_flags & B_CACHE) == 0) {
bp->b_iocmd = BIO_READ;
vfs_busy_pages(bp, 0);
fuse_io_strategy(vp, bp);
if ((err = bp->b_error)) {
brelse(bp);
break;
}
}
if (bp->b_wcred == NOCRED)
bp->b_wcred = crhold(cred);
/*
* If dirtyend exceeds file size, chop it down. This should
* not normally occur but there is an append race where it
* might occur XXX, so we log it.
*
* If the chopping creates a reverse-indexed or degenerate
* situation with dirtyoff/end, we 0 both of them.
*/
if (bp->b_dirtyend > bcount) {
SDT_PROBE2(fusefs, , io, write_biobackend_append_race,
(long)bp->b_blkno * biosize,
bp->b_dirtyend - bcount);
bp->b_dirtyend = bcount;
}
if (bp->b_dirtyoff >= bp->b_dirtyend)
bp->b_dirtyoff = bp->b_dirtyend = 0;
/*
* If the new write will leave a contiguous dirty
* area, just update the b_dirtyoff and b_dirtyend,
* otherwise force a write rpc of the old dirty area.
*
* While it is possible to merge discontiguous writes due to
* our having a B_CACHE buffer ( and thus valid read data
* for the hole), we don't because it could lead to
* significant cache coherency problems with multiple clients,
* especially if locking is implemented later on.
*
* as an optimization we could theoretically maintain
* a linked list of discontinuous areas, but we would still
* have to commit them separately so there isn't much
* advantage to it except perhaps a bit of asynchronization.
*/
if (bp->b_dirtyend > 0 &&
(on > bp->b_dirtyend || (on + n) < bp->b_dirtyoff)) {
/*
* Yes, we mean it. Write out everything to "storage"
* immediately, without hesitation. (Apart from other
* reasons: the only way to know if a write is valid
* if its actually written out.)
*/
SDT_PROBE2(fusefs, , io, write_biobackend_issue, 0, bp);
bwrite(bp);
if (bp->b_error == EINTR) {
err = EINTR;
break;
}
goto again;
}
err = uiomove((char *)bp->b_data + on, n, uio);
if (err) {
bp->b_ioflags |= BIO_ERROR;
bp->b_error = err;
brelse(bp);
break;
/* TODO: vfs_bio_clrbuf like ffs_write does? */
}
/*
* Only update dirtyoff/dirtyend if not a degenerate
* condition.
*/
if (n) {
if (bp->b_dirtyend > 0) {
bp->b_dirtyoff = MIN(on, bp->b_dirtyoff);
bp->b_dirtyend = MAX((on + n), bp->b_dirtyend);
} else {
bp->b_dirtyoff = on;
bp->b_dirtyend = on + n;
}
vfs_bio_set_valid(bp, on, n);
}
vfs_bio_set_flags(bp, ioflag);
if (last_page) {
/*
* When writing the last page of a file we must write
* synchronously. If we didn't, then a subsequent
* operation could extend the file, making the last
* page of this buffer invalid because it would only be
* partially cached.
*
* As an optimization, it would be allowable to only
* write the last page synchronously. Or, it should be
* possible to synchronously flush the last
* already-written page whenever extending a file with
* ftruncate or another write.
*/
SDT_PROBE2(fusefs, , io, write_biobackend_issue, 1, bp);
err = bwrite(bp);
} else if (ioflag & IO_SYNC) {
SDT_PROBE2(fusefs, , io, write_biobackend_issue, 2, bp);
err = bwrite(bp);
} else if (vm_page_count_severe() ||
buf_dirty_count_severe() ||
(ioflag & IO_ASYNC)) {
bp->b_flags |= B_CLUSTEROK;
SDT_PROBE2(fusefs, , io, write_biobackend_issue, 3, bp);
bawrite(bp);
} else if (on == 0 && n == bcount) {
if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERW) == 0) {
bp->b_flags |= B_CLUSTEROK;
SDT_PROBE2(fusefs, , io, write_biobackend_issue,
4, bp);
cluster_write(vp, bp, filesize, seqcount, 0);
} else {
SDT_PROBE2(fusefs, , io, write_biobackend_issue,
5, bp);
bawrite(bp);
}
} else if (ioflag & IO_DIRECT) {
bp->b_flags |= B_CLUSTEROK;
SDT_PROBE2(fusefs, , io, write_biobackend_issue, 6, bp);
bawrite(bp);
} else {
bp->b_flags &= ~B_CLUSTEROK;
SDT_PROBE2(fusefs, , io, write_biobackend_issue, 7, bp);
bdwrite(bp);
}
if (err)
break;
} while (uio->uio_resid > 0 && n > 0);
return (err);
}
int
fuse_io_strategy(struct vnode *vp, struct buf *bp)
{
struct fuse_filehandle *fufh;
struct ucred *cred;
struct uio *uiop;
struct uio uio;
struct iovec io;
off_t filesize;
int error = 0;
int fflag;
/* We don't know the true pid when we're dealing with the cache */
pid_t pid = 0;
const int biosize = fuse_iosize(vp);
MPASS(vp->v_type == VREG || vp->v_type == VDIR);
MPASS(bp->b_iocmd == BIO_READ || bp->b_iocmd == BIO_WRITE);
fflag = bp->b_iocmd == BIO_READ ? FREAD : FWRITE;
cred = bp->b_iocmd == BIO_READ ? bp->b_rcred : bp->b_wcred;
error = fuse_filehandle_getrw(vp, fflag, &fufh, cred, pid);
if (bp->b_iocmd == BIO_READ && error == EBADF) {
/*
* This may be a read-modify-write operation on a cached file
* opened O_WRONLY. The FUSE protocol allows this.
*/
error = fuse_filehandle_get(vp, FWRITE, &fufh, cred, pid);
}
if (error) {
printf("FUSE: strategy: filehandles are closed\n");
bp->b_ioflags |= BIO_ERROR;
bp->b_error = error;
bufdone(bp);
return (error);
}
uiop = &uio;
uiop->uio_iov = &io;
uiop->uio_iovcnt = 1;
uiop->uio_segflg = UIO_SYSSPACE;
uiop->uio_td = curthread;
/*
* clear BIO_ERROR and B_INVAL state prior to initiating the I/O. We
* do this here so we do not have to do it in all the code that
* calls us.
*/
bp->b_flags &= ~B_INVAL;
bp->b_ioflags &= ~BIO_ERROR;
KASSERT(!(bp->b_flags & B_DONE),
("fuse_io_strategy: bp %p already marked done", bp));
if (bp->b_iocmd == BIO_READ) {
io.iov_len = uiop->uio_resid = bp->b_bcount;
io.iov_base = bp->b_data;
uiop->uio_rw = UIO_READ;
uiop->uio_offset = ((off_t)bp->b_lblkno) * biosize;
error = fuse_read_directbackend(vp, uiop, cred, fufh);
if (!error && uiop->uio_resid) {
/*
* If we had a short read with no error, we must have
* hit a file hole. We should zero-fill the remainder.
* This can also occur if the server hits the file EOF.
*
* Holes used to be able to occur due to pending
* writes, but that is not possible any longer.
*/
int nread = bp->b_bcount - uiop->uio_resid;
int left = uiop->uio_resid;
if (left > 0)
bzero((char *)bp->b_data + nread, left);
uiop->uio_resid = 0;
}
if (error) {
bp->b_ioflags |= BIO_ERROR;
bp->b_error = error;
}
} else {
/*
* 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 ((off_t)bp->b_lblkno * biosize + bp->b_dirtyend > filesize)
bp->b_dirtyend = filesize -
(off_t)bp->b_lblkno * biosize;
if (bp->b_dirtyend > bp->b_dirtyoff) {
io.iov_len = uiop->uio_resid = bp->b_dirtyend
- bp->b_dirtyoff;
uiop->uio_offset = (off_t)bp->b_lblkno * biosize
+ bp->b_dirtyoff;
io.iov_base = (char *)bp->b_data + bp->b_dirtyoff;
uiop->uio_rw = UIO_WRITE;
error = fuse_write_directbackend(vp, uiop, cred, fufh,
filesize, 0, false);
if (error == EINTR || error == ETIMEDOUT) {
bp->b_flags &= ~(B_INVAL | B_NOCACHE);
if ((bp->b_flags & B_PAGING) == 0) {
bdirty(bp);
bp->b_flags &= ~B_DONE;
}
if ((error == EINTR || error == ETIMEDOUT) &&
(bp->b_flags & B_ASYNC) == 0)
bp->b_flags |= B_EINTR;
} else {
if (error) {
bp->b_ioflags |= BIO_ERROR;
bp->b_flags |= B_INVAL;
bp->b_error = error;
}
bp->b_dirtyoff = bp->b_dirtyend = 0;
}
} else {
bp->b_resid = 0;
bufdone(bp);
return (0);
}
}
bp->b_resid = uiop->uio_resid;
bufdone(bp);
return (error);
}
int
fuse_io_flushbuf(struct vnode *vp, int waitfor, struct thread *td)
{
return (vn_fsync_buf(vp, waitfor));
}
/*
* Flush and invalidate all dirty buffers. If another process is already
* doing the flush, just wait for completion.
*/
int
fuse_io_invalbuf(struct vnode *vp, struct thread *td)
{
struct fuse_vnode_data *fvdat = VTOFUD(vp);
int error = 0;
if (vp->v_iflag & VI_DOOMED)
return 0;
ASSERT_VOP_ELOCKED(vp, "fuse_io_invalbuf");
while (fvdat->flag & FN_FLUSHINPROG) {
struct proc *p = td->td_proc;
if (vp->v_mount->mnt_kern_flag & MNTK_UNMOUNTF)
return EIO;
fvdat->flag |= FN_FLUSHWANT;
tsleep(&fvdat->flag, PRIBIO + 2, "fusevinv", 2 * hz);
error = 0;
if (p != NULL) {
PROC_LOCK(p);
if (SIGNOTEMPTY(p->p_siglist) ||
SIGNOTEMPTY(td->td_siglist))
error = EINTR;
PROC_UNLOCK(p);
}
if (error == EINTR)
return EINTR;
}
fvdat->flag |= FN_FLUSHINPROG;
if (vp->v_bufobj.bo_object != NULL) {
VM_OBJECT_WLOCK(vp->v_bufobj.bo_object);
vm_object_page_clean(vp->v_bufobj.bo_object, 0, 0, OBJPC_SYNC);
VM_OBJECT_WUNLOCK(vp->v_bufobj.bo_object);
}
error = vinvalbuf(vp, V_SAVE, PCATCH, 0);
while (error) {
if (error == ERESTART || error == EINTR) {
fvdat->flag &= ~FN_FLUSHINPROG;
if (fvdat->flag & FN_FLUSHWANT) {
fvdat->flag &= ~FN_FLUSHWANT;
wakeup(&fvdat->flag);
}
return EINTR;
}
error = vinvalbuf(vp, V_SAVE, PCATCH, 0);
}
fvdat->flag &= ~FN_FLUSHINPROG;
if (fvdat->flag & FN_FLUSHWANT) {
fvdat->flag &= ~FN_FLUSHWANT;
wakeup(&fvdat->flag);
}
return (error);
}
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