Re: [PATCH v9 30/34] qcow2: Add prealloc field to QCowL2Meta

2020-07-03 Thread Max Reitz
On 03.07.20 01:05, Alberto Garcia wrote: > On Thu 02 Jul 2020 05:09:47 PM CEST, Max Reitz wrote: >>> Without a backing file, there is no read required - writing to an >>> unallocated subcluster within a preallocated cluster merely has to >>> provide zeros to the rest of the write.  And depending on

Re: [PATCH v9 30/34] qcow2: Add prealloc field to QCowL2Meta

2020-07-02 Thread Alberto Garcia
On Thu 02 Jul 2020 05:09:47 PM CEST, Max Reitz wrote: >> Without a backing file, there is no read required - writing to an >> unallocated subcluster within a preallocated cluster merely has to >> provide zeros to the rest of the write.  And depending on whether we >> can intelligently guarantee tha

Re: [PATCH v9 30/34] qcow2: Add prealloc field to QCowL2Meta

2020-07-02 Thread Max Reitz
On 02.07.20 16:58, Eric Blake wrote: > On 7/2/20 9:50 AM, Max Reitz wrote: >> On 28.06.20 13:02, Alberto Garcia wrote: >>> This field allows us to indicate that the L2 metadata update does not >>> come from a write request with actual data but from a preallocation >>> request. >>> >>> For tradition

Re: [PATCH v9 30/34] qcow2: Add prealloc field to QCowL2Meta

2020-07-02 Thread Eric Blake
On 7/2/20 9:50 AM, Max Reitz wrote: On 28.06.20 13:02, Alberto Garcia wrote: This field allows us to indicate that the L2 metadata update does not come from a write request with actual data but from a preallocation request. For traditional images this does not make any difference, but for image

Re: [PATCH v9 30/34] qcow2: Add prealloc field to QCowL2Meta

2020-07-02 Thread Max Reitz
On 28.06.20 13:02, Alberto Garcia wrote: > This field allows us to indicate that the L2 metadata update does not > come from a write request with actual data but from a preallocation > request. > > For traditional images this does not make any difference, but for > images with extended L2 entries

[PATCH v9 30/34] qcow2: Add prealloc field to QCowL2Meta

2020-06-28 Thread Alberto Garcia
This field allows us to indicate that the L2 metadata update does not come from a write request with actual data but from a preallocation request. For traditional images this does not make any difference, but for images with extended L2 entries this means that the clusters are allocated normally i