qemu-io: Respect early image end for map

[qemu.git] / qemu-img.texi

diff --git a/qemu-img.texi b/qemu-img.texi
index 4380d5688960ebf93516c42e37df4e775728adab..e3ef4a00e96923f5792fd237fe358b450451587e 100644 (file)
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -228,8 +228,8 @@ compression is read-only. It means that if a compressed sector is
 rewritten, then it is rewritten as uncompressed data.
 
 Image conversion is also useful to get smaller image when using a
-growable format such as @code{qcow} or @code{cow}: the empty sectors
-are detected and suppressed from the destination image.
+growable format such as @code{qcow}: the empty sectors are detected and
+suppressed from the destination image.
 
 @var{sparse_size} indicates the consecutive number of bytes (defaults to 4k)
 that must contain only zeros for qemu-img to create a sparse image during
@@ -341,7 +341,7 @@ string), then the image is rebased onto no backing file (i.e. it will exist
 independently of any backing file).
 
 @var{cache} specifies the cache mode to be used for @var{filename}, whereas
-@var{src_cache} specifies the cache mode for reading the new backing file.
+@var{src_cache} specifies the cache mode for reading backing files.
 
 There are two different modes in which @code{rebase} can operate:
 @table @option
@@ -419,6 +419,15 @@ Linux or NTFS on Windows), then only the written sectors will reserve
 space. Use @code{qemu-img info} to know the real size used by the
 image or @code{ls -ls} on Unix/Linux.
 
+Supported options:
+@table @code
+@item preallocation
+Preallocation mode (allowed values: @code{off}, @code{falloc}, @code{full}).
+@code{falloc} mode preallocates space for image by calling posix_fallocate().
+@code{full} mode preallocates space for image by writing zeros to underlying
+storage.
+@end table
+
 @item qcow2
 QEMU image format, the most versatile format. Use it to have smaller
 images (useful if your filesystem does not supports holes, for example
@@ -467,9 +476,11 @@ sizes can improve the image file size whereas larger cluster sizes generally
 provide better performance.
 
 @item preallocation
-Preallocation mode (allowed values: off, metadata). An image with preallocated
-metadata is initially larger but can improve performance when the image needs
-to grow.
+Preallocation mode (allowed values: @code{off}, @code{metadata}, @code{falloc},
+@code{full}). An image with preallocated metadata is initially larger but can
+improve performance when the image needs to grow. @code{falloc} and @code{full}
+preallocations are like the same options of @code{raw} format, but sets up
+metadata also.
 
 @item lazy_refcounts
 If this option is set to @code{on}, reference count updates are postponed with