Re: [PATCH 1/1] Btrfs: fix sparse warning
> On 05 August 2014 at 23:32 Zach Brown wrote: > > > > > > Hello Zach, > > > > > > > > Here's an untested patch which > > > > > > Try testing it. It's easy with virtualization and xfstests. > > > > > > You'll find that sending to a file fails because each individual file > > > write call that makes up a send starts at offset 0 -- at the start of > > > the file. > > > > > > Getting this right means getting the semantics around updating the send > > > descriptors f_pos right. It requires having a bit of a think about send > > > semantics and f_pos update locking. > > > > Thanks for those informations Zach, > > > > I've tried btrfs test scripts related to ioctl in xfstests (tests/btrfs/025, > > 035, 052, 055) > > but was not able to trigger that problem. Do I have to create another > > script, > > use some generic one > > or maybe use big test/scratch devices ? > > No idea, sorry. Maybe your patch is fine and I'm a dummy. Maybe you > didn't test the kernel you thought you were testing. Maybe the test > doesn't test what you changed. You'll have to do some investigating to > find out. After checking both kernel and btrfs-progs, it seems file offset is only being passed through TLV(see send.c/ send_write/ TLV_PUT_U64(BTRFS_SEND_A_FILE_OFFSET). Tell me if I'm wrong but when we do 'btrfs send backup | btrfs receive backupvolume', btrfs-progs calls btrfs_ioctl_send emitting several BTRFS_SEND_C_WRITE with relevant BTRFS_SEND_A_FILE_OFFSET (growing by 48kb). At the other side of | , 'btrfs receive' executes read_and_process_cmd which does TLV_GET before s->ops->write. All btrfs interactions being done with | maybe we could simply replace vfs_write stuff as you suggested and remove sctx->send_off ? Regards, Fabian > > - z -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 1/1] Btrfs: fix sparse warning
> > > Hello Zach, > > > > > > Here's an untested patch which > > > > Try testing it. It's easy with virtualization and xfstests. > > > > You'll find that sending to a file fails because each individual file > > write call that makes up a send starts at offset 0 -- at the start of > > the file. > > > > Getting this right means getting the semantics around updating the send > > descriptors f_pos right. It requires having a bit of a think about send > > semantics and f_pos update locking. > > Thanks for those informations Zach, > > I've tried btrfs test scripts related to ioctl in xfstests (tests/btrfs/025, > 035, 052, 055) > but was not able to trigger that problem. Do I have to create another script, > use some generic one > or maybe use big test/scratch devices ? No idea, sorry. Maybe your patch is fine and I'm a dummy. Maybe you didn't test the kernel you thought you were testing. Maybe the test doesn't test what you changed. You'll have to do some investigating to find out. - z -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 1/1] Btrfs: fix sparse warning
> On 04 August 2014 at 20:31 Zach Brown wrote: > > > On Sat, Aug 02, 2014 at 02:24:49PM +0200, Fabian Frederick wrote: > > On Thu, 17 Jul 2014 12:01:52 -0700 > > Zach Brown wrote: > > > > > > > > @@ -515,7 +515,8 @@ static int write_buf(struct file *filp, const > > > > > > void *buf, > > > > > > u32 len, loff_t *off) > > > > > > > > > > Though this probably wants to be rewritten in terms of kernel_write(). > > > > > That'd give an opportunity to get rid of the sctx->send_off and have > > > > > it > > > > > use f_pos in the filp. > > > > > > > > Do you mean directly call kernel_write from send_cmd/send_header ? > > > > I guess that loop around vfs_write in write_buf is there for something > > > > ... > > > > > > write_buf() could still exist to iterate over the buffer in the case of > > > partial writes but it doesn't need to muck around with set_fs() and > > > forcing casts. > > > > > > - z > > > > Hello Zach, > > > > Here's an untested patch which > > Try testing it. It's easy with virtualization and xfstests. > > You'll find that sending to a file fails because each individual file > write call that makes up a send starts at offset 0 -- at the start of > the file. > > Getting this right means getting the semantics around updating the send > descriptors f_pos right. It requires having a bit of a think about send > semantics and f_pos update locking. Thanks for those informations Zach, I've tried btrfs test scripts related to ioctl in xfstests (tests/btrfs/025, 035, 052, 055) but was not able to trigger that problem. Do I have to create another script, use some generic one or maybe use big test/scratch devices ? Regards, Fabian > > - z -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 1/1] Btrfs: fix sparse warning
On Sat, Aug 02, 2014 at 02:24:49PM +0200, Fabian Frederick wrote: > On Thu, 17 Jul 2014 12:01:52 -0700 > Zach Brown wrote: > > > > > > @@ -515,7 +515,8 @@ static int write_buf(struct file *filp, const > > > > > void *buf, > > > > > u32 len, loff_t *off) > > > > > > > > Though this probably wants to be rewritten in terms of kernel_write(). > > > > That'd give an opportunity to get rid of the sctx->send_off and have it > > > > use f_pos in the filp. > > > > > > Do you mean directly call kernel_write from send_cmd/send_header ? > > > I guess that loop around vfs_write in write_buf is there for something ... > > > > write_buf() could still exist to iterate over the buffer in the case of > > partial writes but it doesn't need to muck around with set_fs() and > > forcing casts. > > > > - z > > Hello Zach, > > Here's an untested patch which Try testing it. It's easy with virtualization and xfstests. You'll find that sending to a file fails because each individual file write call that makes up a send starts at offset 0 -- at the start of the file. Getting this right means getting the semantics around updating the send descriptors f_pos right. It requires having a bit of a think about send semantics and f_pos update locking. - z -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 1/1] Btrfs: fix sparse warning
On Thu, 17 Jul 2014 12:01:52 -0700
Zach Brown wrote:
> > > > @@ -515,7 +515,8 @@ static int write_buf(struct file *filp, const void
> > > > *buf,
> > > > u32 len, loff_t *off)
> > >
> > > Though this probably wants to be rewritten in terms of kernel_write().
> > > That'd give an opportunity to get rid of the sctx->send_off and have it
> > > use f_pos in the filp.
> >
> > Do you mean directly call kernel_write from send_cmd/send_header ?
> > I guess that loop around vfs_write in write_buf is there for something ...
>
> write_buf() could still exist to iterate over the buffer in the case of
> partial writes but it doesn't need to muck around with set_fs() and
> forcing casts.
>
> - z
Hello Zach,
Here's an untested patch which
-removes send_off and set_fs
-calls kernel_write with ppos 0
but I don't know if something like adding filp->f_pos = pos
at the end of write_buf would be enough to replace send_off ...
Regards,
Fabian
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 6528aa6..a144b4e 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -83,7 +83,6 @@ struct clone_root {
struct send_ctx {
struct file *send_filp;
- loff_t send_off;
char *send_buf;
u32 send_size;
u32 send_max_size;
@@ -505,35 +504,28 @@ static struct btrfs_path *alloc_path_for_send(void)
return path;
}
-static int write_buf(struct file *filp, const void *buf, u32 len, loff_t *off)
+static int write_buf(struct file *filp, const void *buf, u32 len)
{
int ret;
mm_segment_t old_fs;
u32 pos = 0;
- old_fs = get_fs();
- set_fs(KERNEL_DS);
-
while (pos < len) {
- ret = vfs_write(filp, (char *)buf + pos, len - pos, off);
+ ret = kernel_write(filp, (char *)buf + pos, len - pos, 0);
/* TODO handle that correctly */
/*if (ret == -ERESTARTSYS) {
continue;
}*/
if (ret < 0)
- goto out;
+ return ret;
if (ret == 0) {
ret = -EIO;
- goto out;
+ return ret;
}
pos += ret;
}
- ret = 0;
-
-out:
- set_fs(old_fs);
- return ret;
+ return 0;
}
static int tlv_put(struct send_ctx *sctx, u16 attr, const void *data, int len)
@@ -639,8 +631,7 @@ static int send_header(struct send_ctx *sctx)
strcpy(hdr.magic, BTRFS_SEND_STREAM_MAGIC);
hdr.version = cpu_to_le32(BTRFS_SEND_STREAM_VERSION);
- return write_buf(sctx->send_filp, &hdr, sizeof(hdr),
- &sctx->send_off);
+ return write_buf(sctx->send_filp, &hdr, sizeof(hdr));
}
/*
@@ -675,8 +666,7 @@ static int send_cmd(struct send_ctx *sctx)
crc = btrfs_crc32c(0, (unsigned char *)sctx->send_buf, sctx->send_size);
hdr->crc = cpu_to_le32(crc);
- ret = write_buf(sctx->send_filp, sctx->send_buf, sctx->send_size,
- &sctx->send_off);
+ ret = write_buf(sctx->send_filp, sctx->send_buf);
sctx->total_send_size += sctx->send_size;
sctx->cmd_send_size[le16_to_cpu(hdr->cmd)] += sctx->send_size;
--
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Re: [PATCH 1/1] Btrfs: fix sparse warning
> > > @@ -515,7 +515,8 @@ static int write_buf(struct file *filp, const void > > > *buf, > > > u32 len, loff_t *off) > > > > Though this probably wants to be rewritten in terms of kernel_write(). > > That'd give an opportunity to get rid of the sctx->send_off and have it > > use f_pos in the filp. > > Do you mean directly call kernel_write from send_cmd/send_header ? > I guess that loop around vfs_write in write_buf is there for something ... write_buf() could still exist to iterate over the buffer in the case of partial writes but it doesn't need to muck around with set_fs() and forcing casts. - z -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 1/1] Btrfs: fix sparse warning
> On 16 July 2014 at 19:20 Zach Brown wrote: > > > On Tue, Jul 15, 2014 at 09:17:17PM +0200, Fabian Frederick wrote: > > Fix the following sparse warning: > > fs/btrfs/send.c:518:51: warning: incorrect type in argument 2 (different > > address spaces) > > fs/btrfs/send.c:518:51: expected char const [noderef] * > > fs/btrfs/send.c:518:51: got char * > > > > We can safely use (const char __user *) with set_fs(KERNEL_DS) > > Yeah, that cast is correct. > > Reviewed-by: Zach Brown > > > @@ -515,7 +515,8 @@ static int write_buf(struct file *filp, const void *buf, > > u32 len, loff_t *off) > > Though this probably wants to be rewritten in terms of kernel_write(). > That'd give an opportunity to get rid of the sctx->send_off and have it > use f_pos in the filp. Do you mean directly call kernel_write from send_cmd/send_header ? I guess that loop around vfs_write in write_buf is there for something ... Fabian > > - z -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 1/1] Btrfs: fix sparse warning
On Tue, Jul 15, 2014 at 09:17:17PM +0200, Fabian Frederick wrote: > Fix the following sparse warning: > fs/btrfs/send.c:518:51: warning: incorrect type in argument 2 (different > address spaces) > fs/btrfs/send.c:518:51:expected char const [noderef] * > fs/btrfs/send.c:518:51:got char * > > We can safely use (const char __user *) with set_fs(KERNEL_DS) Yeah, that cast is correct. Reviewed-by: Zach Brown > @@ -515,7 +515,8 @@ static int write_buf(struct file *filp, const void *buf, > u32 len, loff_t *off) Though this probably wants to be rewritten in terms of kernel_write(). That'd give an opportunity to get rid of the sctx->send_off and have it use f_pos in the filp. - z -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
