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splice: fix offset mangling with direct splicing (sendfile) 

If the output actor doesn't transfer the full amount of data, we will
increment ppos too much. Two related bugs in there:

- We need to break out and return actor() retval if it is shorted than
  what we spliced into the pipe.

- Adjust ppos only according to actor() return.

Also fix loop problem in generic_file_splice_read(), it should not keep
going when data has already been transferred.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2007-07-13 14:11:43 +02:00
parent 29ce20586b
commit 51a92c0f6c
1 changed files with 11 additions and 23 deletions
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34
fs/splice.c
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@ -492,7 +492,7 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
ret = 0; ret = 0;
spliced = 0; spliced = 0;
while (len) { while (len && !spliced) {
ret = __generic_file_splice_read(in, ppos, pipe, len, flags); ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
if (ret < 0) if (ret < 0)
@ -1060,15 +1060,10 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
sd->flags &= ~SPLICE_F_NONBLOCK; sd->flags &= ~SPLICE_F_NONBLOCK;
while (len) { while (len) {
size_t read_len, max_read_len; size_t read_len;
/* ret = do_splice_to(in, &sd->pos, pipe, len, flags);
* Do at most PIPE_BUFFERS pages worth of transfer: if (unlikely(ret <= 0))
*/
max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
ret = do_splice_to(in, &sd->pos, pipe, max_read_len, flags);
if (unlikely(ret < 0))
goto out_release; goto out_release;
read_len = ret; read_len = ret;
@ -1080,26 +1075,17 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
* could get stuck data in the internal pipe: * could get stuck data in the internal pipe:
*/ */
ret = actor(pipe, sd); ret = actor(pipe, sd);
if (unlikely(ret < 0)) if (unlikely(ret <= 0))
goto out_release; goto out_release;
bytes += ret; bytes += ret;
len -= ret; len -= ret;
/* if (ret < read_len)
* In nonblocking mode, if we got back a short read then goto out_release;
* that was due to either an IO error or due to the
* pagecache entry not being there. In the IO error case
* the _next_ splice attempt will produce a clean IO error
* return value (not a short read), so in both cases it's
* correct to break out of the loop here:
*/
if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
break;
} }
pipe->nrbufs = pipe->curbuf = 0; pipe->nrbufs = pipe->curbuf = 0;
return bytes; return bytes;
out_release: out_release:
@ -1161,10 +1147,12 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
.pos = *ppos, .pos = *ppos,
.u.file = out, .u.file = out,
}; };
size_t ret; long ret;
ret = splice_direct_to_actor(in, &sd, direct_splice_actor); ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
*ppos = sd.pos; if (ret > 0)
*ppos += ret;
return ret; return ret;
} }