[PATCH 1/3] man2/fallocate.2: document behavior with shared blocks
From: Darrick J. Wong <hidden>
Date: 2016-08-25 23:26:36
Also in:
linux-api, linux-fsdevel
Subsystem:
the rest · Maintainer:
Linus Torvalds
Add a blurb to the fallocate manpage explaining that the fallocate command may use CoW to unshare blocks to guarantee that a disk write won't fail with ENOSPC. Signed-off-by: Darrick J. Wong <redacted> --- man2/fallocate.2 | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/man2/fallocate.2 b/man2/fallocate.2
index 54d6340..e050536 100644
--- a/man2/fallocate.2
+++ b/man2/fallocate.2@@ -83,6 +83,12 @@ is useful for optimizing append workloads. Because allocation is done in block size chunks, .BR fallocate () may allocate a larger range of disk space than was specified. +.PP +Filesystems which allow files to share the same physical storage may +employ copy on write to unshare the physical blocks to guarantee that +subsequent writes will not fail due to lack of disk space. +If the disk blocks are then re-shared, a subsequent write may still +fail due to lack of space. .SS Deallocating file space Specifying the .BR FALLOC_FL_PUNCH_HOLE