| Message ID | 1424701661-21241-3-git-send-email-pl@kamp.de |
|---|---|
| State | New |
| Headers | show |
On 2015-02-23 at 09:27, Peter Lieven wrote: > Signed-off-by: Peter Lieven <pl@kamp.de> > --- > block/vpc.c | 116 +++++++++++++++++++++++++++-------------------------------- > 1 file changed, 52 insertions(+), 64 deletions(-) > > diff --git a/block/vpc.c b/block/vpc.c > index 326c2bb..4e5ba85 100644 > --- a/block/vpc.c > +++ b/block/vpc.c > @@ -497,40 +497,70 @@ static int vpc_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) > return 0; > } > > -static int vpc_read(BlockDriverState *bs, int64_t sector_num, > - uint8_t *buf, int nb_sectors) > +static int64_t coroutine_fn vpc_co_get_block_status(BlockDriverState *bs, > + int64_t sector_num, int nb_sectors, int *pnum) How about just putting the function header here? If you really have to move vpc_co_get_block_status() up, I'd rather like it to be in a separate patch. Second, while apparently vpc_read() is actually called in a coroutine, that is pretty hard to know. Most importantly, it's not marked as a coroutine_fn. Therefore I don't think it's a good idea to call vpc_co_get_block_status() directly; I'd vote for either using bdrv_get_block_status(), or moving the content of vpc_co_get_block_status() to a non-coroutine_fn (it doesn't contain an coroutine-related function calls, so this is fine) and then making vpc_co_get_block_status() a wrapper around that, or just dropping this patch. The latter I'm proposing because I don't really see what this patch improves. The previous vpc_read() function was pretty straightforward, too, and I don't think it was unbearably longer. One could argue that the coroutine_fn stuff doesn't really matter in this situation because it doesn't actually do anything right now and vpc_co_get_block_status() does not call any other coroutine_fn functions in turn; however, it is a semantic contract established by include/block/coroutine.h and as far as I remember, Stefan did eventually want to have something to error out on compile-time if a non-coroutine_fn function calls a coroutine_fn. I don't like breaking this contract even if it's not bad in this specific case. Considering you probably think bdrv_get_block_status() to be too much overhead (it will fall down to the protocol layer on VHD_FIXED) and you probably find making vpc_read() shorter justified (again, which I don't necessarily), I think moving the contents of vpc_co_get_block_status() to a non-coroutine_fn might be the best way to go. > { > BDRVVPCState *s = bs->opaque; > - int ret; > - int64_t offset; > - int64_t sectors, sectors_per_block; > - VHDFooter *footer = (VHDFooter *) s->footer_buf; > + VHDFooter *footer = (VHDFooter*) s->footer_buf; > + int64_t start, offset; > + bool allocated; > + int n; > > if (be32_to_cpu(footer->type) == VHD_FIXED) { > - return bdrv_read(bs->file, sector_num, buf, nb_sectors); > + *pnum = nb_sectors; > + return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_DATA | > + (sector_num << BDRV_SECTOR_BITS); > } > - while (nb_sectors > 0) { > - offset = get_sector_offset(bs, sector_num, 0); > > - sectors_per_block = s->block_size >> BDRV_SECTOR_BITS; > - sectors = sectors_per_block - (sector_num % sectors_per_block); > - if (sectors > nb_sectors) { > - sectors = nb_sectors; > + offset = get_sector_offset(bs, sector_num, 0); > + start = offset; > + allocated = (offset != -1); > + *pnum = 0; > + > + do { > + /* All sectors in a block are contiguous (without using the bitmap) */ > + n = ROUND_UP(sector_num + 1, s->block_size / BDRV_SECTOR_SIZE) > + - sector_num; > + n = MIN(n, nb_sectors); > + > + *pnum += n; > + sector_num += n; > + nb_sectors -= n; > + > + if (allocated) { > + return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID | start; > } > + if (nb_sectors == 0) { > + break; > + } > + offset = get_sector_offset(bs, sector_num, 0); > + } while (offset == -1); > > - if (offset == -1) { > - memset(buf, 0, sectors * BDRV_SECTOR_SIZE); > - } else { > - ret = bdrv_pread(bs->file, offset, buf, > - sectors * BDRV_SECTOR_SIZE); > - if (ret != sectors * BDRV_SECTOR_SIZE) { > + return 0; > +} > + > +static int vpc_read(BlockDriverState *bs, int64_t sector_num, > + uint8_t *buf, int nb_sectors) > +{ > + int ret, n; > + int64_t ret2; > + > + while (nb_sectors > 0) { > + ret2 = vpc_co_get_block_status(bs, sector_num, nb_sectors, &n); > + Superfluous whitespace here. > + if (ret2 & BDRV_BLOCK_OFFSET_VALID) { > + ret = bdrv_pread(bs->file, ret2 & BDRV_SECTOR_MASK, buf, > + n * BDRV_SECTOR_SIZE); > + if (ret != n * BDRV_SECTOR_SIZE) { > return -1; Please make that "return ret" (and possibly "if (ret < 0)", if you want to). Max > } > + } else { > + memset(buf, 0x00, n * BDRV_SECTOR_SIZE); > } > > - nb_sectors -= sectors; > - sector_num += sectors; > - buf += sectors * BDRV_SECTOR_SIZE; > + sector_num += n; > + nb_sectors -= n; > + buf += n * BDRV_SECTOR_SIZE; > } > return 0; > } > @@ -597,48 +627,6 @@ static coroutine_fn int vpc_co_write(BlockDriverState *bs, int64_t sector_num, > return ret; > } > > -static int64_t coroutine_fn vpc_co_get_block_status(BlockDriverState *bs, > - int64_t sector_num, int nb_sectors, int *pnum) > -{ > - BDRVVPCState *s = bs->opaque; > - VHDFooter *footer = (VHDFooter*) s->footer_buf; > - int64_t start, offset; > - bool allocated; > - int n; > - > - if (be32_to_cpu(footer->type) == VHD_FIXED) { > - *pnum = nb_sectors; > - return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_DATA | > - (sector_num << BDRV_SECTOR_BITS); > - } > - > - offset = get_sector_offset(bs, sector_num, 0); > - start = offset; > - allocated = (offset != -1); > - *pnum = 0; > - > - do { > - /* All sectors in a block are contiguous (without using the bitmap) */ > - n = ROUND_UP(sector_num + 1, s->block_size / BDRV_SECTOR_SIZE) > - - sector_num; > - n = MIN(n, nb_sectors); > - > - *pnum += n; > - sector_num += n; > - nb_sectors -= n; > - > - if (allocated) { > - return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID | start; > - } > - if (nb_sectors == 0) { > - break; > - } > - offset = get_sector_offset(bs, sector_num, 0); > - } while (offset == -1); > - > - return 0; > -} > - > /* > * Calculates the number of cylinders, heads and sectors per cylinder > * based on a given number of sectors. This is the algorithm described
Am 23.02.2015 um 19:29 schrieb Max Reitz: > On 2015-02-23 at 09:27, Peter Lieven wrote: >> Signed-off-by: Peter Lieven <pl@kamp.de> >> --- >> block/vpc.c | 116 +++++++++++++++++++++++++++-------------------------------- >> 1 file changed, 52 insertions(+), 64 deletions(-) >> >> diff --git a/block/vpc.c b/block/vpc.c >> index 326c2bb..4e5ba85 100644 >> --- a/block/vpc.c >> +++ b/block/vpc.c >> @@ -497,40 +497,70 @@ static int vpc_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) >> return 0; >> } >> -static int vpc_read(BlockDriverState *bs, int64_t sector_num, >> - uint8_t *buf, int nb_sectors) >> +static int64_t coroutine_fn vpc_co_get_block_status(BlockDriverState *bs, >> + int64_t sector_num, int nb_sectors, int *pnum) > > How about just putting the function header here? If you really have to move vpc_co_get_block_status() up, I'd rather like it to be in a separate patch. > > Second, while apparently vpc_read() is actually called in a coroutine, that is pretty hard to know. Most importantly, it's not marked as a coroutine_fn. Therefore I don't think it's a good idea to call vpc_co_get_block_status() directly; I'd vote for > either using bdrv_get_block_status(), or moving the content of vpc_co_get_block_status() to a non-coroutine_fn (it doesn't contain an coroutine-related function calls, so this is fine) and then making vpc_co_get_block_status() a wrapper around that, or > just dropping this patch. > > The latter I'm proposing because I don't really see what this patch improves. The previous vpc_read() function was pretty straightforward, too, and I don't think it was unbearably longer. > > One could argue that the coroutine_fn stuff doesn't really matter in this situation because it doesn't actually do anything right now and vpc_co_get_block_status() does not call any other coroutine_fn functions in turn; however, it is a semantic > contract established by include/block/coroutine.h and as far as I remember, Stefan did eventually want to have something to error out on compile-time if a non-coroutine_fn function calls a coroutine_fn. I don't like breaking this contract even if it's > not bad in this specific case. > > Considering you probably think bdrv_get_block_status() to be too much overhead (it will fall down to the protocol layer on VHD_FIXED) and you probably find making vpc_read() shorter justified (again, which I don't necessarily), I think moving the > contents of vpc_co_get_block_status() to a non-coroutine_fn might be the best way to go. > >> { >> BDRVVPCState *s = bs->opaque; >> - int ret; >> - int64_t offset; >> - int64_t sectors, sectors_per_block; >> - VHDFooter *footer = (VHDFooter *) s->footer_buf; >> + VHDFooter *footer = (VHDFooter*) s->footer_buf; >> + int64_t start, offset; >> + bool allocated; >> + int n; >> if (be32_to_cpu(footer->type) == VHD_FIXED) { >> - return bdrv_read(bs->file, sector_num, buf, nb_sectors); >> + *pnum = nb_sectors; >> + return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_DATA | >> + (sector_num << BDRV_SECTOR_BITS); >> } >> - while (nb_sectors > 0) { >> - offset = get_sector_offset(bs, sector_num, 0); >> - sectors_per_block = s->block_size >> BDRV_SECTOR_BITS; >> - sectors = sectors_per_block - (sector_num % sectors_per_block); >> - if (sectors > nb_sectors) { >> - sectors = nb_sectors; >> + offset = get_sector_offset(bs, sector_num, 0); >> + start = offset; >> + allocated = (offset != -1); >> + *pnum = 0; >> + >> + do { >> + /* All sectors in a block are contiguous (without using the bitmap) */ >> + n = ROUND_UP(sector_num + 1, s->block_size / BDRV_SECTOR_SIZE) >> + - sector_num; >> + n = MIN(n, nb_sectors); >> + >> + *pnum += n; >> + sector_num += n; >> + nb_sectors -= n; >> + >> + if (allocated) { >> + return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID | start; >> } >> + if (nb_sectors == 0) { >> + break; >> + } >> + offset = get_sector_offset(bs, sector_num, 0); >> + } while (offset == -1); >> - if (offset == -1) { >> - memset(buf, 0, sectors * BDRV_SECTOR_SIZE); >> - } else { >> - ret = bdrv_pread(bs->file, offset, buf, >> - sectors * BDRV_SECTOR_SIZE); >> - if (ret != sectors * BDRV_SECTOR_SIZE) { >> + return 0; >> +} >> + >> +static int vpc_read(BlockDriverState *bs, int64_t sector_num, >> + uint8_t *buf, int nb_sectors) >> +{ >> + int ret, n; >> + int64_t ret2; >> + >> + while (nb_sectors > 0) { >> + ret2 = vpc_co_get_block_status(bs, sector_num, nb_sectors, &n); >> + > > Superfluous whitespace here. > >> + if (ret2 & BDRV_BLOCK_OFFSET_VALID) { >> + ret = bdrv_pread(bs->file, ret2 & BDRV_SECTOR_MASK, buf, >> + n * BDRV_SECTOR_SIZE); >> + if (ret != n * BDRV_SECTOR_SIZE) { >> return -1; > > Please make that "return ret" (and possibly "if (ret < 0)", if you want to). I took this from the orignal vpc_read function. Maybe the author also wanted to catch short reads. I tend to drop the whole patch anyway. I was tempted to use that new vpc_co_get_block_status function somehow because I saw that part of its logic is in vpc_read as well. If it should stay maybe it would be an option to inline vpc_read in vpc_co_read (and the same for write)?
On 2015-02-24 at 01:44, Peter Lieven wrote: > Am 23.02.2015 um 19:29 schrieb Max Reitz: >> On 2015-02-23 at 09:27, Peter Lieven wrote: >>> Signed-off-by: Peter Lieven <pl@kamp.de> >>> --- >>> block/vpc.c | 116 >>> +++++++++++++++++++++++++++-------------------------------- >>> 1 file changed, 52 insertions(+), 64 deletions(-) >>> >>> diff --git a/block/vpc.c b/block/vpc.c >>> index 326c2bb..4e5ba85 100644 >>> --- a/block/vpc.c >>> +++ b/block/vpc.c >>> @@ -497,40 +497,70 @@ static int vpc_get_info(BlockDriverState *bs, >>> BlockDriverInfo *bdi) >>> return 0; >>> } >>> -static int vpc_read(BlockDriverState *bs, int64_t sector_num, >>> - uint8_t *buf, int nb_sectors) >>> +static int64_t coroutine_fn >>> vpc_co_get_block_status(BlockDriverState *bs, >>> + int64_t sector_num, int nb_sectors, int *pnum) >> >> How about just putting the function header here? If you really have >> to move vpc_co_get_block_status() up, I'd rather like it to be in a >> separate patch. >> >> Second, while apparently vpc_read() is actually called in a >> coroutine, that is pretty hard to know. Most importantly, it's not >> marked as a coroutine_fn. Therefore I don't think it's a good idea to >> call vpc_co_get_block_status() directly; I'd vote for either using >> bdrv_get_block_status(), or moving the content of >> vpc_co_get_block_status() to a non-coroutine_fn (it doesn't contain >> an coroutine-related function calls, so this is fine) and then making >> vpc_co_get_block_status() a wrapper around that, or just dropping >> this patch. >> >> The latter I'm proposing because I don't really see what this patch >> improves. The previous vpc_read() function was pretty >> straightforward, too, and I don't think it was unbearably longer. >> >> One could argue that the coroutine_fn stuff doesn't really matter in >> this situation because it doesn't actually do anything right now and >> vpc_co_get_block_status() does not call any other coroutine_fn >> functions in turn; however, it is a semantic contract established by >> include/block/coroutine.h and as far as I remember, Stefan did >> eventually want to have something to error out on compile-time if a >> non-coroutine_fn function calls a coroutine_fn. I don't like breaking >> this contract even if it's not bad in this specific case. >> >> Considering you probably think bdrv_get_block_status() to be too much >> overhead (it will fall down to the protocol layer on VHD_FIXED) and >> you probably find making vpc_read() shorter justified (again, which I >> don't necessarily), I think moving the contents of >> vpc_co_get_block_status() to a non-coroutine_fn might be the best way >> to go. >> >>> { >>> BDRVVPCState *s = bs->opaque; >>> - int ret; >>> - int64_t offset; >>> - int64_t sectors, sectors_per_block; >>> - VHDFooter *footer = (VHDFooter *) s->footer_buf; >>> + VHDFooter *footer = (VHDFooter*) s->footer_buf; >>> + int64_t start, offset; >>> + bool allocated; >>> + int n; >>> if (be32_to_cpu(footer->type) == VHD_FIXED) { >>> - return bdrv_read(bs->file, sector_num, buf, nb_sectors); >>> + *pnum = nb_sectors; >>> + return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | >>> BDRV_BLOCK_DATA | >>> + (sector_num << BDRV_SECTOR_BITS); >>> } >>> - while (nb_sectors > 0) { >>> - offset = get_sector_offset(bs, sector_num, 0); >>> - sectors_per_block = s->block_size >> BDRV_SECTOR_BITS; >>> - sectors = sectors_per_block - (sector_num % >>> sectors_per_block); >>> - if (sectors > nb_sectors) { >>> - sectors = nb_sectors; >>> + offset = get_sector_offset(bs, sector_num, 0); >>> + start = offset; >>> + allocated = (offset != -1); >>> + *pnum = 0; >>> + >>> + do { >>> + /* All sectors in a block are contiguous (without using the >>> bitmap) */ >>> + n = ROUND_UP(sector_num + 1, s->block_size / BDRV_SECTOR_SIZE) >>> + - sector_num; >>> + n = MIN(n, nb_sectors); >>> + >>> + *pnum += n; >>> + sector_num += n; >>> + nb_sectors -= n; >>> + >>> + if (allocated) { >>> + return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID | start; >>> } >>> + if (nb_sectors == 0) { >>> + break; >>> + } >>> + offset = get_sector_offset(bs, sector_num, 0); >>> + } while (offset == -1); >>> - if (offset == -1) { >>> - memset(buf, 0, sectors * BDRV_SECTOR_SIZE); >>> - } else { >>> - ret = bdrv_pread(bs->file, offset, buf, >>> - sectors * BDRV_SECTOR_SIZE); >>> - if (ret != sectors * BDRV_SECTOR_SIZE) { >>> + return 0; >>> +} >>> + >>> +static int vpc_read(BlockDriverState *bs, int64_t sector_num, >>> + uint8_t *buf, int nb_sectors) >>> +{ >>> + int ret, n; >>> + int64_t ret2; >>> + >>> + while (nb_sectors > 0) { >>> + ret2 = vpc_co_get_block_status(bs, sector_num, nb_sectors, >>> &n); >>> + >> >> Superfluous whitespace here. >> >>> + if (ret2 & BDRV_BLOCK_OFFSET_VALID) { >>> + ret = bdrv_pread(bs->file, ret2 & BDRV_SECTOR_MASK, buf, >>> + n * BDRV_SECTOR_SIZE); >>> + if (ret != n * BDRV_SECTOR_SIZE) { >>> return -1; >> >> Please make that "return ret" (and possibly "if (ret < 0)", if you >> want to). > > I took this from the orignal vpc_read function. Maybe the author also > wanted > to catch short reads. There are no short reads (any more), though. ;-) > I tend to drop the whole patch anyway. I was tempted to use that new > vpc_co_get_block_status > function somehow because I saw that part of its logic is in vpc_read > as well. > > If it should stay maybe it would be an option to inline vpc_read in > vpc_co_read (and the same for write)? Oh, I totally missed the vpc_co_read(). That would make sense, because you actually can call vpc_co_get_block_status() from there, or you just add the coroutine_fn specifier to vpc_read(). It's up to you, I'm fine with all of dropping, inlining, and making vpc_read() a coroutine_fn. Max
diff --git a/block/vpc.c b/block/vpc.c index 326c2bb..4e5ba85 100644 --- a/block/vpc.c +++ b/block/vpc.c @@ -497,40 +497,70 @@ static int vpc_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) return 0; } -static int vpc_read(BlockDriverState *bs, int64_t sector_num, - uint8_t *buf, int nb_sectors) +static int64_t coroutine_fn vpc_co_get_block_status(BlockDriverState *bs, + int64_t sector_num, int nb_sectors, int *pnum) { BDRVVPCState *s = bs->opaque; - int ret; - int64_t offset; - int64_t sectors, sectors_per_block; - VHDFooter *footer = (VHDFooter *) s->footer_buf; + VHDFooter *footer = (VHDFooter*) s->footer_buf; + int64_t start, offset; + bool allocated; + int n; if (be32_to_cpu(footer->type) == VHD_FIXED) { - return bdrv_read(bs->file, sector_num, buf, nb_sectors); + *pnum = nb_sectors; + return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_DATA | + (sector_num << BDRV_SECTOR_BITS); } - while (nb_sectors > 0) { - offset = get_sector_offset(bs, sector_num, 0); - sectors_per_block = s->block_size >> BDRV_SECTOR_BITS; - sectors = sectors_per_block - (sector_num % sectors_per_block); - if (sectors > nb_sectors) { - sectors = nb_sectors; + offset = get_sector_offset(bs, sector_num, 0); + start = offset; + allocated = (offset != -1); + *pnum = 0; + + do { + /* All sectors in a block are contiguous (without using the bitmap) */ + n = ROUND_UP(sector_num + 1, s->block_size / BDRV_SECTOR_SIZE) + - sector_num; + n = MIN(n, nb_sectors); + + *pnum += n; + sector_num += n; + nb_sectors -= n; + + if (allocated) { + return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID | start; } + if (nb_sectors == 0) { + break; + } + offset = get_sector_offset(bs, sector_num, 0); + } while (offset == -1); - if (offset == -1) { - memset(buf, 0, sectors * BDRV_SECTOR_SIZE); - } else { - ret = bdrv_pread(bs->file, offset, buf, - sectors * BDRV_SECTOR_SIZE); - if (ret != sectors * BDRV_SECTOR_SIZE) { + return 0; +} + +static int vpc_read(BlockDriverState *bs, int64_t sector_num, + uint8_t *buf, int nb_sectors) +{ + int ret, n; + int64_t ret2; + + while (nb_sectors > 0) { + ret2 = vpc_co_get_block_status(bs, sector_num, nb_sectors, &n); + + if (ret2 & BDRV_BLOCK_OFFSET_VALID) { + ret = bdrv_pread(bs->file, ret2 & BDRV_SECTOR_MASK, buf, + n * BDRV_SECTOR_SIZE); + if (ret != n * BDRV_SECTOR_SIZE) { return -1; } + } else { + memset(buf, 0x00, n * BDRV_SECTOR_SIZE); } - nb_sectors -= sectors; - sector_num += sectors; - buf += sectors * BDRV_SECTOR_SIZE; + sector_num += n; + nb_sectors -= n; + buf += n * BDRV_SECTOR_SIZE; } return 0; } @@ -597,48 +627,6 @@ static coroutine_fn int vpc_co_write(BlockDriverState *bs, int64_t sector_num, return ret; } -static int64_t coroutine_fn vpc_co_get_block_status(BlockDriverState *bs, - int64_t sector_num, int nb_sectors, int *pnum) -{ - BDRVVPCState *s = bs->opaque; - VHDFooter *footer = (VHDFooter*) s->footer_buf; - int64_t start, offset; - bool allocated; - int n; - - if (be32_to_cpu(footer->type) == VHD_FIXED) { - *pnum = nb_sectors; - return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_DATA | - (sector_num << BDRV_SECTOR_BITS); - } - - offset = get_sector_offset(bs, sector_num, 0); - start = offset; - allocated = (offset != -1); - *pnum = 0; - - do { - /* All sectors in a block are contiguous (without using the bitmap) */ - n = ROUND_UP(sector_num + 1, s->block_size / BDRV_SECTOR_SIZE) - - sector_num; - n = MIN(n, nb_sectors); - - *pnum += n; - sector_num += n; - nb_sectors -= n; - - if (allocated) { - return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID | start; - } - if (nb_sectors == 0) { - break; - } - offset = get_sector_offset(bs, sector_num, 0); - } while (offset == -1); - - return 0; -} - /* * Calculates the number of cylinders, heads and sectors per cylinder * based on a given number of sectors. This is the algorithm described
Signed-off-by: Peter Lieven <pl@kamp.de> --- block/vpc.c | 116 +++++++++++++++++++++++++++-------------------------------- 1 file changed, 52 insertions(+), 64 deletions(-)