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fusefs: diff reduction between fuse_read_biobackend and ext_read

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The main difference is to replace some custom logic with bread.  No
functional change at this point, but this is one step towards adding
readahead.

Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Alan Somers 2019-04-23 22:34:32 +00:00
parent 3746a90aef
commit 21d4686c5c
1 changed files with 19 additions and 38 deletions
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57
sys/fs/fuse/fuse_io.c
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@ -110,7 +110,7 @@ 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,
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,
@ -160,7 +160,8 @@ fuse_io_dispatch(struct vnode *vp, struct uio *uio, int ioflag,
} else {
SDT_PROBE2(fusefs, , io, trace, 1,
"buffered read of vnode");
err = fuse_read_biobackend(vp, uio, cred, fufh, pid);
err = fuse_read_biobackend(vp, uio, ioflag, cred, fufh,
pid);
}
break;
case UIO_WRITE:
@ -198,71 +199,51 @@ SDT_PROBE_DEFINE3(fusefs, , io, read_bio_backend_start, "int", "int", "int");
SDT_PROBE_DEFINE2(fusefs, , io, read_bio_backend_feed, "int", "int");
SDT_PROBE_DEFINE3(fusefs, , io, read_bio_backend_end, "int", "ssize_t", "int");
static int
fuse_read_biobackend(struct vnode *vp, struct uio *uio,
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 = 0, n = 0, on = 0;
int err, n = 0, on = 0;
off_t filesize;
const int biosize = fuse_iosize(vp);
if (uio->uio_resid == 0)
return (0);
if (uio->uio_offset < 0)
return (EINVAL);
bcount = biosize;
filesize = VTOFUD(vp)->filesize;
do {
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);
SDT_PROBE3(fusefs, , io, read_bio_backend_start,
biosize, (int)lbn, on);
/*
* Obtain the buffer cache block. Figure out the buffer size
* when we are at EOF. If we are modifying the size of the
* buffer based on an EOF condition we need to hold
* nfs_rslock() through obtaining the buffer to prevent
* a potential writer-appender from messing with n_size.
* Otherwise we may accidentally truncate the buffer and
* lose dirty data.
*
* Note that bcount is *not* DEV_BSIZE aligned.
*/
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;
}
bp = getblk(vp, lbn, bcount, PCATCH, 0, 0);
if (!bp)
return (EINTR);
/*
* If B_CACHE is not set, we must issue the read. If this
* fails, we return an error.
*/
if ((bp->b_flags & B_CACHE) == 0) {
bp->b_iocmd = BIO_READ;
vfs_busy_pages(bp, 0);
err = fuse_io_strategy(vp, bp);
if (err) {
brelse(bp);
return (err);
}
/* 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
@ -279,10 +260,10 @@ fuse_read_biobackend(struct vnode *vp, struct uio *uio,
n, n + (int)bp->b_resid);
err = uiomove(bp->b_data + on, n, uio);
}
brelse(bp);
vfs_bio_brelse(bp, ioflag);
SDT_PROBE3(fusefs, , io, read_bio_backend_end, err,
uio->uio_resid, n);
} while (err == 0 && uio->uio_resid > 0 && n > 0);
}
return (err);
}