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Message-ID: <20070625214626.GJ5181@schatzie.adilger.int> Date: Mon, 25 Jun 2007 15:46:26 -0600 From: Andreas Dilger <adilger@...sterfs.com> To: "Amit K. Arora" <aarora@...ux.vnet.ibm.com> Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org, David Chinner <dgc@....com>, suparna@...ibm.com, cmm@...ibm.com, xfs@....sgi.com Subject: Re: [PATCH 4/7][TAKE5] support new modes in fallocate On Jun 25, 2007 20:33 +0530, Amit K. Arora wrote: > I have not implemented FA_FL_FREE_ENOSPC and FA_ZERO_SPACE flags yet, as > *suggested* by Andreas in http://lkml.org/lkml/2007/6/14/323 post. > If it is decided that these flags are also needed, I will update this > patch. Thanks! Can you clarify - what is the current behaviour when ENOSPC (or some other error) is hit? Does it keep the current fallocate() or does it free it? For FA_ZERO_SPACE - I'd think this would (IMHO) be the default - we don't want to expose uninitialized disk blocks to userspace. I'm not sure if this makes sense at all. > On Mon, Jun 25, 2007 at 07:15:00PM +0530, Amit K. Arora wrote: > > Implement new flags and values for mode argument. > > > > This patch implements the new flags and values for the "mode" argument > > of the fallocate system call. It is based on the discussion between > > Andreas Dilger and David Chinner on the man page proposed (by the later) > > on fallocate. > > > > Signed-off-by: Amit Arora <aarora@...ibm.com> > > > > Index: linux-2.6.22-rc4/include/linux/fs.h > > =================================================================== > > --- linux-2.6.22-rc4.orig/include/linux/fs.h > > +++ linux-2.6.22-rc4/include/linux/fs.h > > @@ -267,15 +267,16 @@ extern int dir_notify_enable; > > #define SYNC_FILE_RANGE_WAIT_AFTER 4 > > > > /* > > - * sys_fallocate modes > > - * Currently sys_fallocate supports two modes: > > - * FA_ALLOCATE : This is the preallocate mode, using which an application/user > > - * may request (pre)allocation of blocks. > > - * FA_DEALLOCATE: This is the deallocate mode, which can be used to free > > - * the preallocated blocks. > > + * sys_fallocate mode flags and values > > */ > > -#define FA_ALLOCATE 0x1 > > -#define FA_DEALLOCATE 0x2 > > +#define FA_FL_DEALLOC 0x01 /* default is allocate */ > > +#define FA_FL_KEEP_SIZE 0x02 /* default is extend/shrink size */ > > +#define FA_FL_DEL_DATA 0x04 /* default is keep written data on DEALLOC */ > > + > > +#define FA_ALLOCATE 0 > > +#define FA_DEALLOCATE FA_FL_DEALLOC > > +#define FA_RESV_SPACE FA_FL_KEEP_SIZE > > +#define FA_UNRESV_SPACE (FA_FL_DEALLOC | FA_FL_KEEP_SIZE | FA_FL_DEL_DATA) > > > > #ifdef __KERNEL__ > > > > Index: linux-2.6.22-rc4/fs/open.c > > =================================================================== > > --- linux-2.6.22-rc4.orig/fs/open.c > > +++ linux-2.6.22-rc4/fs/open.c > > @@ -356,23 +356,26 @@ asmlinkage long sys_ftruncate64(unsigned > > * sys_fallocate - preallocate blocks or free preallocated blocks > > * @fd: the file descriptor > > * @mode: mode specifies if fallocate should preallocate blocks OR free > > - * (unallocate) preallocated blocks. Currently only FA_ALLOCATE and > > - * FA_DEALLOCATE modes are supported. > > + * (unallocate) preallocated blocks. > > * @offset: The offset within file, from where (un)allocation is being > > * requested. It should not have a negative value. > > * @len: The amount (in bytes) of space to be (un)allocated, from the offset. > > * > > * This system call, depending on the mode, preallocates or unallocates blocks > > * for a file. The range of blocks depends on the value of offset and len > > - * arguments provided by the user/application. For FA_ALLOCATE mode, if this > > + * arguments provided by the user/application. For FA_ALLOCATE and > > + * FA_RESV_SPACE modes, if the sys_fallocate() > > * system call succeeds, subsequent writes to the file in the given range > > * (specified by offset & len) should not fail - even if the file system > > * later becomes full. Hence the preallocation done is persistent (valid > > - * even after reopen of the file and remount/reboot). > > + * even after reopen of the file and remount/reboot). If FA_RESV_SPACE mode > > + * is passed, the file size will not be changed even if the preallocation > > + * is beyond EOF. > > * > > * It is expected that the ->fallocate() inode operation implemented by the > > * individual file systems will update the file size and/or ctime/mtime > > - * depending on the mode and also on the success of the operation. > > + * depending on the mode (change is visible to user or not - say file size) > > + * and obviously, on the success of the operation. > > * > > * Note: Incase the file system does not support preallocation, > > * posix_fallocate() should fall back to the library implementation (i.e. > > @@ -398,7 +401,8 @@ asmlinkage long sys_fallocate(int fd, in > > > > /* Return error if mode is not supported */ > > ret = -EOPNOTSUPP; > > - if (mode != FA_ALLOCATE && mode != FA_DEALLOCATE) > > + if (!(mode == FA_ALLOCATE || mode == FA_DEALLOCATE || > > + mode == FA_RESV_SPACE || mode == FA_UNRESV_SPACE)) > > goto out; > > > > ret = -EBADF; > > - > > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > > the body of a message to majordomo@...r.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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